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The objectives of this study were to identify factors associated with the relative change in prepartum DMI (RCDMI) of 273 cows fed individually, evaluate the performance of linear models to estimate RCDMI using different classes of predictors, and characterize the implications of RCDMI to transition metabolism, health, and subsequent milk production. Two periods of interest were established. Period 1 comprised d −21 to −12 relative to calving, when DMI was stable. Period 2 comprised d −4 to −1, when average DMI was distinctly declined. The RCDMI from period 1 to 2 was calculated as a percentage value, which ranged from −75% to 15% and averaged −18.1% (± 15.0%). Season, parity, body fatness, body weight, milk production in the previous lactation and at dry-off, and length of dry period were associated with RCDMI and explained 11% of the variation in all cows, and 19% when only parous cows were considered. Performance of linear models to predict RCDMI was improved when data on rumination and physical activities and target blood metabolites were added. The adjusted R2 increased to values between 0.45 and 0.55, and selected models performed consistently in cross-validation analyses. To evaluate the implications of RCDMI, cows were ranked within parity according to RCDMI and classified into terciles as large decline (LDec), moderate decline (MDec), or small decline (SDec). By design, DMI did not differ between tercile groups in period 1 (13.3 ± 0.2 kg/d), but differed substantially in period 2 (LDec = 8.8; MDec = 11.2; SDec = 12.7 ± 0.2 kg/d), creating important differences in RCDMI among groups (LDec = −33.8; MDec = −16.2; SDec = −3.4% ± 0.8%). At enrollment, cows in the LDec and MDec groups were heavier (LDec = 788; MDec = 775; SDec = 750 ± 7 kg), and the proportion of cows with BCS >3.5 was higher in LDec (LDec = 63%; MDec = 47%; SDec = 38%). An interaction between group and time was observed for postpartum DMI, which started lower in LDec than in SDec cows, equaled by the end of transition, and inverted at wk 13 and 14 after calving. Yields of ECM were greater in LDec than in SDec cows, and both groups did not differ from MDec (LDec = 41.0; MDec = 40.3; SDec = 39.0 ± 0.5 kg/d). The LDec cows had decreased energy balance and greater concentrations of nonesterified fatty acids, β-hydroxybutyrate, and aspartate aminotransferase in serum, and greater glutathione peroxidase activity in plasma than SDec cows. Larger declines in prepartum DMI were also associated with increased risk for postpartum disease, although the associations were only weak to moderate. In conclusion, a large decline in prepartum DMI of cows fed ad libitum was associated with important adjustments in the energy metabolism and antioxidants activities, and greater milk production in the subsequent lactation. These findings indicate that feed intake decline close to parturition is likely a normal response to physiological adaptations at the onset of lactation when cows are fed ad libitum. The list of standard abbreviations for JDS is available at adsa.org/jds-abbreviations-24. Nonstandard abbreviations are available in the Notes. [ABSTRACT FROM AUTHOR]

The list of standard abbreviations for JDS is available at adsa.org/jds-abbreviations-24. Nonstandard abbreviations are available in the Notes. A meta-analysis was performed to investigate the effects of capsaicin (CAP) on lactational performance and blood chemistry and cell counts in dairy cattle. The database comprised 11 peer-reviewed studies published between 2011 and 2024. The overall effect of CAP, challenge (e.g., ketosis, glucose tolerance, LPS), and dose were considered explanatory variables in the analysis. Lactation performance response variables included DMI, milk yield (MY), ECM yield, feed efficiency (FE), milk components, and BW. Hematological response variables included red and white blood cell counts and blood BHB, total fatty acids, insulin, and glucose concentrations. Data were analyzed using random- and mixed-effect models in the "robumeta" package in RStudio. Milk yield was increased by 2.9% by CAP when compared with control. Capsaicin supplementation increased FE by 3.4% compared with control. Milk fat concentration and yield were also increased by CAP compared with control by 2.6% and 4.0%, respectively. Blood glucose concentrations were decreased 2.5% by CAP supplementation, whereas insulin levels were unaffected. Cows fed CAP during a challenge had higher MY and FE and tended to have lower blood glucose than their control counterparts. Overall, this analysis suggests that CAP supplementation may be directly affecting host physiology by altering glucose metabolism, but further research to define the mechanism is warranted. [ABSTRACT FROM AUTHOR]

India is the largest milk producer contributing 25 % to the global production. From a mere 17 million tons (MTs) in 1951, milk production increased to an inconceivable 230 MTs in 2023. Nondescript cows and buffaloes were the main milk animals. Since 1965, nationwide programs for cross breeding native cattle with exotic milk breeds such as Jersey, Holstein Friesian (HF) and Brown Swiss (BS) and upgradation of buffalo breeds along with disease eradication, feed and fodder development and provision of veterinary and extension services were implemented. Now 75 % of the milk in India is produced by the native, exotic and crossbred cows (43 %) and native breeds of buffaloes (32 %). National Dairy Development Board (NDDB) created dairy cooperatives, an Indian innovation to connect rural milk producers to urban and semi-urban consumers. These cooperatives transformed subsistence dairy farming into a profitable rural enterprise and created millions of jobs. Due to the success of the above activities, since 1998 India continues to produce the highest volumes of milk in the world. It is envisioned to increase (i) milk production to 450 million tons (MTs) (one-third of the global production) (ii) gain a share of 15 % in global milk and milk products exports and (iii) build sustainable green practices to match global standards during the next 25 years. India is increasingly deploying artificial insemination (AI) with sex sorted-frozen semen, embryo transfer and in vitro production of embryos using sex sorted semen, progeny testing and genomic selection to improve reproduction and productivity among dairy animals. Mitigation of disease burden is undertaken through nationwide vaccination against diseases such as Foot and Mouth, TB, Brucellosis etc. Nutritious fodder crops and feed additives that support higher productivity and reduce enteric methane emissions are promoted. Management and interventional practices such as better nutrition, amelioration of summer stress, oestrus synchronisation etc., are increasingly implemented. Use of internet enabled technology services (IETS) for extension activities, mobile veterinary and animal husbandry services are rapidly becoming commonplace. All these practices portend greater achievements in milk production in the fore-seeable future. Achievements, aspirations, accosts, approaches and appraisal are presented. • 1950–70: India was milk deficit country. • 1965–98: White revolution: crossbreeding and upgradation of native bovines to become world's top milk producer. • 1998–2023: Technology supported milk production: India remains the top milk producer in the world. • 2023-50: Intensification of technology adoption: India shall remain world's top milk producer. [ABSTRACT FROM AUTHOR]

The objective was to evaluate the effects of separate offering of feed ingredients (SF) and frequency of concentrate feeding versus offering a TMR, on lactational performance, ruminal fermentation, enteric CH 4 emissions, nutrient digestibility, N use efficiency, milk fatty acid profile, and blood variables in mid-lactation dairy cows. Twenty-four Holstein cows (12 primi- and 12 multiparous) averaging (±SD) 141 ± 35 DIM and 43 ± 6 kg/d of milk yield (MY) at the beginning of the study were used in a replicated 3 × 3 Latin square design experiment with 3 periods of 28 d each, composed of 7 d for adaptation to the diets, 11 d for estimation of net energy and metabolizable protein requirements, and 10 d for data and samples collection. Cows were grouped based on parity, DIM, and MY into 4 Latin squares. Treatment allocation was balanced for carryover effects, and cows within square were assigned to (1) basal diet fed ad libitum as TMR; (2) basal diet fed as SF with forages fed ad libitum and concentrates fed 3×/d (SF×3); or (3) basal diet fed as SF with forages fed ad libitum and concentrates fed 6×/d (SF×6). Compared with TMR, SF decreased total DMI by 1.2 kg/d. Treatments did not affect MY, milk components, or ECM yield, except for a decrease in milk fat concentration and an increase in milk urea N by SF×3, compared with TMR. Feed efficiency (kg of MY/kg of DMI) was increased by 7% in SF, compared with TMR. Ruminal molar proportion of acetate and acetate-to-propionate ratio were decreased, whereas molar proportion of propionate was increased by SF×3, compared with TMR and SF×6. There was a 9% decrease in daily CH 4 production by SF, compared with TMR. Enteric CH 4 yield (per kg of DMI) was not affected by treatments in the current study. Methane intensity per kilogram of MY tended to be decreased by 10% in SF, compared with TMR. The sums of odd- and branched-chain, odd-chain, and anteiso milk fatty acids tended to be or were increased by SF, compared with TMR. Intake of nutrients tended to be or were decreased by SF, compared with TMR. The digestibility of amylase-treated NDF tended to be decreased and ADF digestibility was decreased by 3% in SF, compared with TMR. Urinary and fecal N excretions were not affected by treatments. As a percentage of total N intake, separate offering of feed ingredients increased milk N secretion, indicating an increased N use efficiency by SF, compared with TMR. Blood total fatty acid concentration was decreased by SF relative to TMR. Compared with both TMR and SF×6, SF×3 increased blood urea N concentration. Overall, feed and N use efficiencies were increased by separate offering of feed ingredients, and increasing the frequency of concentrate feeding promoted ruminal fermentation effects similar to those obtained by feeding a TMR. [ABSTRACT FROM AUTHOR]

Adequate energy supply is a crucial factor for maintaining the production performance in cows during the early lactation period. Adding fatty acids (FA) to diets can improve energy supply, and the effect could be related to the chain length and degree of saturation of those FA. This study was conducted to evaluate the effect of different ratios of palmitic acid (C16:0) to oleic acid (cis -9 C18:1) on the production performance, nutrient digestibility, blood metabolites, and milk FA profile in early lactation dairy cows. Seventy-two multiparous Holstein cows (63.5 ± 2.61 days in milk) blocked by parity (2.39 ± 0.20), body weight (668.3 ± 20.1 kg), body condition score (3.29 ± 0.06), and milk yield (47.9 ± 1.63 kg) were used in a completely randomized design. Cows were divided into 3 groups with 24 cows in each group. Cows in the 3 treatment groups were provided iso-energy and iso-nitrogen diets, but the C16:0 to cis -9 C18:1 ratios were different: (1) 90.9% C16:0 + 9.1% cis -9 C18:1 (90.9:9.1); (2) 79.5% C16:0 + 20.5% cis -9 C18:1 (79.5:20.5); and (3) 72.7% C16:0 + 27.3% cis -9 C18:1 (72.7:27.3). Fatty acids were added at 1.3% on a dry matter basis. Although the dry matter intake fat-corrected milk yield and energy-corrected milk yield were not affected, the milk yield, milk protein yield, and feed efficiency increased linearly with increasing cis -9 C18:1 ratio. The milk protein percentage and milk fat yield did not differ among treatments, whereas the milk fat percentage tended to decrease linearly with the increasing cis -9 C18:1 ratio. The lactose yield increased linearly and lactose percentage tended to increase linearly with increasing cis -9 C18:1 ratio, but the percentage of milk total solids and somatic cell count decreased linearly. Although body condition scores were not affected by treatments, body weight loss decreased linearly with increasing cis -9 C18:1 ratio. The effect of treatment on nutrient digestibility was limited, except for a linear increase in ether extract and neutral detergent fiber digestibility with increasing cis -9 C18:1 ratio. There was a linear increase in the concentration of plasma glucose, but the triglyceride and nonesterified FA concentrations decreased linearly with increasing cis -9 C18:1 ratio. As the cis -9 C18:1 ratio increased, the concentration of de novo FA decreased quadratically, but the mixed and preformed fatty acids increased linearly. In conclusion, increasing cis -9 C18:1 ratio could increase production performance and decrease body weight loss by increasing nutrient digestibility, and the ratio that had the most powerful beneficial effect on early lactation cows was 72.7:27.3 (C16:0 to cis -9 C18:1). [ABSTRACT FROM AUTHOR]

The aim of the present study was to assess the effect of replacing the forage portion (alfalfa, corn silage, and barley straw) in the diet of lactating Holstein cows with triticale hay (TH, × Triticosecale L.) on DMI, digestibility, ruminal fermentation variables, estimated microbial-N synthesis (EMNS), and milk production and composition. Eight Holstein cows were used in a replicated Latin square design (two 4 × 4 squares) with four 28-d periods and 4 treatments, including a TH-free diet (control), and diets replacing 33%, 66%, and 100% of the forage portion with TH. Cows were fed ad libitum with 10% carryover during the experimental periods. Intakes and in vivo digestibilities of dry matter, organic matter, crude protein, and ash-free neutral detergent fiber, rumen pH, ammonia-N, total and individual short-chain fatty acids, protozoa, and bacteria populations were evaluated using specific methods. Moreover, in vitro total gas and methane release and in vivo urinary purine derivatives, EMNS, milk production, and composition were measured. The results showed that TH diets lowered DMI, compared with the control. Apparent digestibilities of DM, OM, CP, and NDF increased with dietary TH inclusion. The addition of TH instead of the diet forage portion increased in vivo rumen pH; acetic, propionic, valeric, and isovaleric acids concentrations; cellulolytic bacteria number; and in vitro gas production. In vivo rumen ammonia-N, short-chain fatty acids, butyric acid, in vivo and in vitro total protozoa and Entodiniinae numbers, and in vitro methane production decreased with increasing dietary levels of TH instead of the forage portion. The dietary addition of TH did not affect milk yield, protein, and lactose, but increased fat-corrected milk, milk fat, fat-corrected milk:DMI ratio, and milk yield:DMI ratio. Milk urea N decreased, but urinary purine derivatives excretion and EMNS increased with increasing levels of TH in the diet. For variables with significant changes, except for isovaleric acid, there was a linear response of animals to increasing levels of TH in the diet. Results suggest that TH, which is grown with less water compared with alfalfa, corn forage, and straw, is a potential alternative to those forages by increasing milk production efficiency, milk fat, and decreasing methane emission. [ABSTRACT FROM AUTHOR]

Heat stress compromises dairy production by decreasing feed intake and milk yield, and it may also alter milk composition and feed efficiency. However, little information is available for evaluating such effects across different levels of heat stress and cows enrolled in heat stress studies. The objectives of this study were to evaluate the effects of heat stress on dry matter intake (DMI), energy-corrected milk (ECM), milk composition, and feed efficiency (kg ECM/kg DMI) and to investigate the relationship between such effects and heat stress intervention and animal characteristics by using meta-analytical approaches. Data from 31 studies (34 trials) fulfilled the inclusion criteria and were used for analysis. Results showed that heat stress decreased DMI, ECM, and milk protein concentration, but did not alter milk fat concentration or feed efficiency. Meta-regression confirmed that such reductions in DMI and ECM were significantly associated with increasing temperature-humidity index (THI). Over the period of heat stress, for each unit increase in THI, DMI and ECM decreased by 4.13% and 3.25%, respectively, in mid-lactation cows. Regression models further revealed the existence of a strong interaction between THI and lactation stage, which partially explained the large heterogeneity in effect sizes of DMI and ECM. The results indicated a need for more research on the relationship between the effect of heat stress and animal characteristics. This study calls for the implementation of mitigation strategies in heat-stressed herds due to the substantial decrease in productivity. [ABSTRACT FROM AUTHOR]

In dairy cows, the lactating mammary glands synthesize serotonin, which acts in an autocrine-paracrine manner in the glands and is secreted into the periphery. Serotonin signaling during lactation modulates nutrient metabolism in peripheral tissues such as adipose and liver. We hypothesized that the elevation of circulating serotonin during lactation would increase nutrient partitioning to the mammary glands, thereby promoting milk production. Our objective was to elevate circulating serotonin via intravenous infusion of the serotonin precursor 5-hydroxytryptophan (5-HTP) to determine its effects on mammary supply and extraction efficiency of AA, and milk components production. Twenty-two multiparous mid-lactation Holstein cows were intravenously infused with 5-HTP (1 mg/kg body weight) or saline, in a crossover design with two 21-d periods. Treatments were infused via jugular catheters for 1 h/d, on d 1 to 3, 8 to 10, and 15 to 17 of each period, to maintain consistent elevation of peripheral serotonin throughout the period. Milk and blood samples were collected in the last 96 h of each period. Whole-blood serotonin concentration was elevated above saline control for 96 h after the last 5-HTP infusion. Dry matter intake was decreased for cows receiving 5-HTP, and on average they lost body weight over the 21-d period, in contrast to saline cows who gained body weight. Milk production and milk protein yield were lower in cows receiving 5-HTP during the 3 infusion days, but both recovered to saline cow yields in the days after. Although milk fat yield exhibited a day-by-treatment interaction, no significant difference occurred on any given day. Milk urea nitrogen concentration was lower in 5-HTP cows on the days following the end of infusions, but not different from saline cows on infusion days. Meanwhile, plasma urea nitrogen was not affected by 5-HTP infusion. Circulating concentrations of AA were overall transiently decreased by 5-HTP, with concentrations mostly returning to baseline within 7 h after the end of 5-HTP infusion. Mammary extraction efficiency of AA was unaffected by 5-HTP infusion. Overall, both lactation performance and circulating AA were transiently reduced in cows infused with 5-HTP, despite sustained elevation of circulating serotonin concentration. [ABSTRACT FROM AUTHOR]

The objective of this study was to quantify the farm gate nitrogen (N) offset potential of perennial ryegrass (Lolium perenne L.; PRG) white clover (Trifolium repens L.; WC) swards by comparing the herbage and milk production from dairy farmlets that were simulations of full farming systems. A study was established where 120 cows were randomly assigned to 4 farmlets of 10.9 ha (stocking rate: 2.75 cow/ha), composed of 20 paddocks each. Cows were fed 526 kg of DM of concentrate on average each year. The 4 grazing treatments were PRG-only at 150 or 250 kg of N/ha and PRG-WC at 150 or 250 kg of N/ha. Cows remained in their treatment group for an entire grazing season and were re-randomized as they calved across treatments each year. As cows calved in the spring as standard practice in Ireland, they were rotationally grazed from early February both day and night (weather permitting) to mid-November, to a target postgrazing sward height of 4.0 cm. Mean sward WC content was 18.1% and 15.4% for the 150 and 250 kg of N/ha PRG-WC treatments, respectively over the 3-yr period. When WC was included, lowering the N rate did not reduce pregrazing yield, pregrazing height, or herbage removed, but those factors decreased significantly when WC was absent. Total annual herbage DM production was 13,771, 15,242, 14,721, and 15,667 kg of DM/ha for PRG-only swards receiving 150 or 250 kg of N/ha and PRG-WC swards receiving 150 or 250 kg of N/ha, respectively. In addition, when WC was present, compressed postgrazing sward heights were lower (4.10 vs. 4.21 cm) and herbage allowance (approximately 17 kg/cow feed allocation per cow per day) higher than the high-N control (+ 0.7 kg of DM/cow per day). There was a significant increase in milk production, both per cow and per hectare, when WC was included in PRG swards. Over the 3-yr study, cows grazing PRG-WC had greater milk (+304 kg) and milk solids (+31 kg of fat + protein) yields than cows grazing PRG-only swards. This significant increase in milk production suggests that the inclusion of WC in grazing systems can be effectively used to increase milk production per cow and per hectare and help offset nitrogen use. This result shows the potential to increase farm gate N use efficiency and reduce the N surplus compared with PRG-dominant sward grazing systems receiving 250 kg of N/ha, without negatively affecting milk solids yield or herbage production, thus increasing farm profit by €478/ha. [ABSTRACT FROM AUTHOR]

The objective of this study was to evaluate lactational performance, enteric gas emissions, ruminal fermentation, nutrient use efficiency, milk fatty acid profile, and energy and inflammatory markers in blood of peak-lactation dairy cows fed diets supplemented with Capsicum oleoresin or a combination of Capsicum oleoresin and clove oil. A 10-wk randomized complete block design experiment was conducted with 18 primiparous and 30 multiparous Holstein cows. Cows were blocked based on parity, days in milk, and milk yield (MY), and randomly assigned to 1 of 3 treatments (16 cows/treatment): (1) basal diet (CON); (2) basal diet supplemented with 300 mg/cow per day of Capsicum oleoresin (CAP); and (3) basal diet supplemented with 300 mg/cow per day of a combination of Capsicum oleoresin and clove oil (CAPCO). Premixes containing ground corn (CON), CAP, or CAPCO were mixed daily with the basal diet at 0.8% of dry matter intake (DMI). Supplementation of the diet with CAP or CAPCO did not affect DMI, MY, milk components, and feed efficiency of the cows. Body weight (BW) was increased during the last 2 wk of the experiment by CAP and CAPCO, compared with CON. The botanicals improved BW gain (0.85 and 0.66 kg/d for CAP and CAPCO, respectively, compared with −0.01 kg/d for CON) and CAP enhanced the efficiency of energy utilization, compared with CON (94.5% vs. 78.4%, respectively). Daily CH 4 emission was not affected by treatments, but CH 4 emission yield (per kg of DMI) and intensity (per kg of MY) were decreased by up to 11% by CAPCO supplementation, compared with CON and CAP. A treatment × parity interaction indicated that the CH 4 mitigation effect was pronounced in primiparous but not in multiparous cows. Ruminal molar proportion of propionate was decreased by botanicals, compared with CON. Concentrations of trans -10 C18:1 and total trans fatty acids in milk fat were decreased by CAP and tended to be decreased by CAPCO, compared with CON. Total-tract apparent digestibility of nutrients was not affected by treatments, except for a tendency for decreased starch digestibility in cows supplemented with botanicals. Blood concentrations of β-hydroxybutyrate, total fatty acids, and insulin were not affected by botanicals. Blood haptoglobin concentration was increased by CAP in multiparous but not in primiparous cows. Lactational performance of peak-lactation dairy cows was not affected by the botanicals in this study, but they appeared to improve efficiency of energy utilization and partitioned energy toward BW gain. In addition, CH 4 yield and intensity were decreased in primiparous cows fed CAPCO, suggesting a potential positive environmental effect of the combination of Capsicum oleoresin and clove oil supplementation. [ABSTRACT FROM AUTHOR]

[Display omitted] • A life cycle costing method was developed to optimize the cow raising system. • Using manure as fertilizer yields the greatest environmental and economic benefits. • Manure management choices are responsible for 58% of the carbon footprint variation. • Investment in fertilizer utilization yields up to a 3-fold environmental benefit. • Chinese milk production may reach a carbon peak value of 69 Mt CO 2 eq by 2057. Waste management signifies an equilibrium between environmental and economic factors. However, a comprehensive understanding of the integrated life cycle environmental-economic performance of waste management activities remains unclear. To facilitate a systematic linkage between the economic and environmental sectors, a regionalized life cycle assessment-based life cycle costing method was developed based on China's actual status quo. The cow manure utilization was set as an entry point to explored long-term environmental-economic performance of milk production under various manure utilization pathways. The results show that trade-offs were observed between internal and external costs as well as various environmental indicators. The choice of waste utilization is the focal point of environmental-economic trade-offs in the cow raising system. The optimal environmental-economic performance was achieved through the manure fertilizer utilization pathway, yielding a remarkable three-fold increase in marginal environmental benefits. Compared with fertilizer utilization, the manure direct returning to field reduced the carbon footprint by 12% while induced an external cost of $14.3. The wastewater treatment pathway is $ 5.5 lower in internal costs but $ 11.7 higher in external costs than those of fertilizer utilization. Overall, utilizing manure has potential to mitigate the upward trend of carbon footprint and external costs. However, achieving the carbon peak remains a significant challenge. A promising solution is the recycling of straw resources within cropping systems, particularly in hotspot regions (e.g., Inner Mongolia, Heilongjiang, Hebei, and Shandong). A comprehensive analysis of the dynamic interplay between cropping systems and cow raising systems is critical steps towards realizing a carbon-neutral future within the dairy production. [ABSTRACT FROM AUTHOR]

Globally, the majority of dairy cows are milked twice a day (TAD); however, in pasture-based production systems, such as in Ireland, the idea of milking once a day (OAD) is being considered for reasons such as improved work-life balance. The immediate effects within a lactation, as well as the multilactation consequences of OAD, compared with TAD milking, require understanding. The objective of this randomized experiment was to compare OAD and TAD milking, over a 3-yr period, by examining the differences in milk production and composition, body weight (BW), body condition score (BCS), dry matter intake (DMI), udder characteristics, locomotion score, and milking time. Over the 3-yr period, 83 cows were enrolled in the experiment; 32, 44, and 48 cows in yr 1, 2, and 3 of the experiment, respectively. Each year, 23% of the herds were primiparous animals, while the remainder were second lactation or greater in parity. All cows were milked in the morning at 0700 h; only cows milked TAD were milked a second time each day at 1600 h. Cows rotationally grazed pastures for the duration of the lactating period and were housed during the nonlactating period. Milking cows OAD reduced cumulative milk yield by 26%, and milk solids yield (kg of fat + kg of protein) by 21%, across the 3 yr of the experiment when compared with cows milked TAD which produced 4,126 and 365 kg/cow, respectively. A contributory factor to the reduced production was a shorter lactation length (9.7 d) of the cows milked OAD compared with TAD (294 d). Milk fat percent of cows milked TAD was similar for all 3 yr of the study (5.05%), whereas milk fat percent of the cows milked OAD increased year on year, with each year being greater than the previous year (5.02%, 5.32%, and 5.70% for yr 1, 2, and 3; respectively). Milk protein percent was greater (+0.19%) for cows milked OAD compared with TAD which was 3.78%. Compared with cows milked TAD, total DMI for cows milked OAD was 22% less at the start of lactation (<167 d), but as the lactation progressed (>167 d) we observed no difference in DMI between treatments. Similar to the literature, milking cows OAD significantly increased average somatic cell score, both during (+16%) and at the end of lactation (+19%), compared with milking cows TAD which were 4.69 and 4.79, respectively. We detected positive aspects associated with OAD milking such as greater BW, BCS, and fertility performance. Milking OAD reduced both milking time per cow per day (reductions ranged from 34% in the first 4 mo of lactation to 43% during mo 5–9 of lactation) and milking time per liter of milk (−3.5 s/L) throughout lactation, leading to less labor inputs on-farm which can have positive implications for farmer work-life balance. The significant time saving and potential savings in costs (e.g., electricity) need to be considered in conjunction with the milk production reduction when considering OAD milking for the entire lactation. [ABSTRACT FROM AUTHOR]

Effects of replacing canola meal with dehulled hemp meal in the diet of lactating dairy cows on the dry matter intake (DMI), milk production, milk fatty acid profile, blood metabolites, total-tract nutrient digestibility, and transfer of cannabinoids were determined in 12 lactating, nonpregnant Holstein cows. These cows were used in a 3 × 3 Latin square design with three 3-wk experimental periods consisting of 2 wk of adaptation and 1 wk of sampling. Cows received basal partial mixed rations supplemented with either 15% dry matter (DM) canola meal (CM15), 15% DM dehulled hemp meal (HM15), or 7.5% DM dehulled hemp meal and 7.5% DM canola meal (CM7.5HM7.5). Diets were formulated to be isoenergetic and isonitrogenous, but the HM15 and CM7.5HM7.5 diets contained, on average 1.2 percentage units more crude protein (CP) that the CM15 diet. The CP of the dehulled hemp meal contained less soluble protein than that of canola meal. Hence, the intake of soluble protein did not differ among diets. Canola meal contained less crude fat than hemp seed meal (3.46% vs. 8.25% DM). The lipid fraction of canola meal fat contained more oleic acid (C18:1 cis -9; 47.3 vs. 14.9 g/100 g of fatty acids, FA) and vaccenic acid (18:1 cis -11; 13.7 vs. 1.2 g/100 g of FA) and less linoleic acid (C18:2n-6; 21.9 vs. 55.7 g/100 g of FA) and α linolenic acid (C18:3n-3; 3.2 vs. 8.9 g/100 g of FA) than the lipid fraction of hemp seed meal. The hemp seed meal contained 4.9 µg/g cannabidiol, 5.1 µg/g cannabidiolic acid, and 0.1 µg/g tertahydroxycannabinolic acid A. Treatments did not differ in DMI, yields of milk, milk protein and milk fat, total-tract neutral detergent fiber digestibility, and blood plasma concentrations of β-hydroxybutyrate and nonesterified FA. Apparent total-tract DM digestibility was lowest in the HM15 treatment, whereas the CP digestibility and the concentrations of urea in blood, urine, and milk were lowest in the CM15 treatment. Cannabinoids were not detected in urine, milk, and blood plasma. Replacing canola meal with hemp seed meal increased milk fat contents of polyunsaturated fatty acids (PUFA), which were 3.42, 3.90, and 4.25 g/100 g of FA for the CM15, CM7.5HM7.5, and HM15 treatments, respectively. Especially, the milk fat contents of 18:2n-6 (1.99 vs. 1.56 g/100 g FA) and 18:3n-3 (0.31 vs. 0.43 g/100 g FA) were increased by hemp meal feeding. Especially, the milk fat contents of 18:2n-6 (1.99 vs. 1.56 g/100 g FA) and 18:3n-3 (0.31 vs. 0.43 g/100 g FA) were increased by hemp meal feeding. Our data show that hemp seed meal is a suitable and safe replacement for canola meal as a feed for lactating dairy cows and that this replacement increases CP digestibility and urea in urine, milk, and blood plasma, as well the PUFA content of milk fat. [ABSTRACT FROM AUTHOR]

We evaluated the effects of supplementing bacterial direct-fed microbial (DFM) on performance, apparent total-tract digestibility, rumen fermentation, and immune parameters of lactating dairy cows. One hundred fourteen multiparous Holstein cows (41 ± 7 DIM) were used in a randomized complete block design with an experiment comprising 14 d of a covariate (pre-experimental sample and data collection) and 91 d of an experimental period. Cows were blocked based on energy-corrected milk (ECM) yield during the covariate period and the following treatments were randomly assigned within each block: (1) control (CON), corn silage-based total mixed ration without DFM; (2) PRO-A, basal diet top-dressed with a mixture of Lactobacillus animalis and Propionibacterium freudenreichii at 3 × 109 cfu/d; and 3) PRO-B, basal diet top-dressed with a mixture of L. animalis , P. freudenreichii , Bacillus subtilis , and Bacillus licheniformis at 11.8 × 109 cfu/d. Milk yield, dry matter intake (DMI), and body weight were measured daily, while milk samples for component analysis were taken on 2 consecutive days of each week of data collection. Feces, urine, rumen, and blood samples were taken during the covariate period, wk 4, 7, 10, and 13 for estimation of digestibility, N-partitioning, rumen fermentation, plasma nutrient status and immune parameters. Treatments had no effect on DMI and milk yield. Fat-corrected milk (3.5% FCM) and milk fat yield were improved with PRO-B, while milk fat percent and feed efficiency (ECM/DMI) tended to increase with PRO-B compared with PRO-A and CON. Crude fat digestibility was greater with PRO-B compared with CON. Feeding CON and PRO-A resulted in higher total volatile fatty acid concentration relative to PRO-B. Percentage of neutrophils tended to be reduced with PRO-A compared with CON and PRO-B. The mean fluorescence intensity (MFI) of anti-CD44 antibody on granulocytes tended to be higher in PRO-B compared with CON. The MFI of anti-CD62L antibody on CD8+ T cells was lower in PRO-A than PRO-B, with PRO-A also showing a tendency to be lower than CON. This study indicates the potential of DFM to improve fat digestibility with consequential improvement in fat corrected milk yield, feed efficiency and milk fat yield by lactating dairy cows. The study findings also indicate that dietary supplementation with DFM may augment immune parameters or activation of immune cells, including granulocytes and T cells; however, the overall effects on immune parameters are inconclusive. [ABSTRACT FROM AUTHOR]

The objective of this experiment was to investigate the effects of an essential oil (EO) blend on lactational performance, rumen fermentation, nutrient utilization, blood variables, enteric methane emissions and manure greenhouse gas-emitting potential in dairy cows. A randomized complete block design experiment was conducted with 26 primiparous and 22 multiparous Holstein cows. A 2-wk covariate and a 2-wk adaptation periods preceded a 10-wk experimental period used for data and sample collection. Treatments were: (1) basal diet supplemented with placebo (CON); and (2) basal diet supplemented with a blend of EO containing eugenol and geranyl acetate as main compounds. Supplementation with EO did not affect dry matter intake, milk and energy-corrected milk yields, and feed efficiency of cows, compared with CON. Milk fat and lactose concentrations were increased, and milk total solids (TS) concentration and milk fat yield tended to be increased by EO. Multiparous cows supplemented with EO tended to have slightly decreased dry matter and crude protein digestibility compared with CON multiparous cows. There was a tendency for increased ruminal pH by EO, whereas other rumen fermentation variables did not differ between treatments. Daily methane emission was not affected by EO supplementation, but methane emission intensity per kg of milk fat was decreased by 8.5% by EO. Methane emission intensity per kg of milk lactose and milk TS were decreased and methane emission intensity per kg of milk yield tended to be decreased by up to 10% in EO multiparous cows, but not in primiparous cows. The greenhouse gas-emitting potential of manure was not affected by EO supplementation. Compared with CON, fecal nitrogen excretion was increased by EO supplementation in multiparous, but not in primiparous cows, and milk nitrogen secretion (as a % of nitrogen intake) tended to be increased in EO supplemented cows. Blood variables were not affected by EO supplementation in the current study. Overall, dietary supplementation of EO did not affect lactational performance of the cows, although milk fat and lactose concentrations were increased. Most enteric methane emission metrics were not affected, but EO decreased methane intensity per kg of milk fat by 8.5%, compared with the control. [ABSTRACT FROM AUTHOR]

Allowing dairy cattle to access pasture or outdoor areas is known to be beneficial for cows' welfare and is considered important by the general public. However, in confinement-based operations with high-yielding cows, pasture access may be difficult to implement, especially for lactating animals. Providing pasture access to heifers and dry cows seems a more feasible option for most farms. The objective of this study was to investigate the effects of providing high-yielding dairy cows with free-choice pasture access during the dry period on their health, behavior, and milk production. Over the study period, a total of 78 Holstein cows were assigned to 1 of 2 treatments during the dry period (51 ± 8 d): housing with free-choice access to the pasture (PAST) or housing continuously without any access to the outdoors (CTRL). After calving, all cows from both treatments were mixed and housed continuously. To assess the effects of the treatment on cows' performance, all animals enrolled were monitored both before calving and during the first 100 d in milk of the following lactation. The behavior of all cows involved was monitored continuously during the whole observation period using collar-based sensors. All cows were inspected monthly to assess lameness, hock lesions, cleanliness, and body condition score. During the period after calving (0–100 d in milk), milk production and composition were also monitored. Results showed that free-choice pasture access affected cows' feeding behavior. Before calving, the animals in PAST spent more time feeding than in CTRL and, interestingly, this difference tended to persist for several weeks after calving. During the dry period, cows in PAST were cleaner than in CTRL but no differences in locomotion and body condition score were found between the 2 groups. Free-choice pasture access during the dry period also affected milk production during the following lactation. The cows that spent the dry period in PAST produced more milk than CTRL counterparts, particularly for the animals that calved during summer. In the current study we have found that providing free-choice pasture access during the dry period can positively affect the performance of dairy cattle and represents a desirable practice in confinement-based dairy production systems. [ABSTRACT FROM AUTHOR]

Chromosome X is often excluded from bovine genetic studies due to complications caused by the sex specific nature of the chromosome. As chromosome X is the second largest cattle chromosome and makes up approximately 6% of the female genome, finding ways to include chromosome X in dairy genetic studies is important. Using female animals and treating chromosome X as an autosome, we performed X chromosome inclusive genome-wide association studies in the selective breeding environment of the New Zealand dairy industry, aiming to identify chromosome X variants associated with milk production traits. We report on the findings of these genome-wide association studies and their potential effect within the dairy industry. We identify missense mutations in the MOSPD1 and CCDC160 genes that are associated with decreased milk volume and protein production and increased fat production. Both of these mutations are exonic SNP that are more prevalent in the Jersey breed than in Holstein-Friesians. Of the 2 candidates proposed it is likely that only one is causal, though we have not been able to identify which is more likely. [ABSTRACT FROM AUTHOR]

Enteric fermentation from dairy cows is a major source of methane. Significantly and rapidly reducing those emissions would be a powerful lever to mitigate climate change. For a given productivity level, introducing fodder with high sources of n-3 content, such as grass or linseed, in the feed ration of dairy cows both improves the milk nutritional profile and reduces enteric methane emissions per liter. Changing cows' diet may represent additional costs for dairy farmers and calls for the implementation of payments for environmental services to support the transition. This paper analyzes 2 design elements influencing the effectiveness of a payment conditioned toward the reduction of enteric methane emissions: (1) the choice of emission indicator capturing the effect of farmers' practices, and (2) the payment amount relative to the additional milk production costs incurred. Using representative farm-level economic data from the French farm accountancy data network, we compare enteric methane emissions per liter of milk calculated with an Intergovernmental Panel on Climate Change Tier 2 method, to baseline emissions from a Tier 3 method accounting for diet effects. We also quantify the additional milk production costs of integrating more grass in the fodder systems by estimating variable cost functions for different dairy systems in France. Our results show the relevance of using an emission indicator sensitive to diet effects, and that the significance and direction of the additional costs for producing milk with a diet containing more grass differ according to the production basin and the current share of grasslands in the fodder crop rotation. We emphasize the importance of developing payments for environmental services with well-defined environmental indicators accounting for the technical problems addressed, and the need to better characterize heterogeneous funding requirements for supporting a large-scale adoption of more environment-friendly practices by farmers. [ABSTRACT FROM AUTHOR]

The objective of this meta-analysis was to examine the effects of supplemental His on lactational performance, plasma His concentration and efficiency of utilization of digestible His (Eff His) in dairy cows. The meta-analysis was performed on data from 17 studies published in peer-reviewed journals between 1999 and 2022. Five publications reported data from 2 separate experiments, which were included in the analyses as separate studies, therefore resulting in a total of 22 studies. In 10 studies, His was supplemented as rumen-protected (RP) His; in 1 study, 2 basal diets with different dHis levels were fed; and in the remaining experiments, free His was infused into the abomasum (4 studies), the jugular vein (3 studies) or deleted from a mixture of postruminally infused AA (4 studies). The main forages in the diets were corn silage in 14 and grass silage in 8 studies. If not reported in the publications, the supplies of dietary CP, metabolizable protein (MP), net energy of lactation, and digestible His (dHis) were estimated using NRC (2001). An initial meta-analysis was performed to test the standard mean difference (SMD; raw mean difference of treatment and control means divided by the pooled standard deviation of the means), that is, effect size, and the corresponding 95% confidence interval (CI) in production parameters between His-supplemented groups versus control. Further, regression analyses were also conducted to examine and compare the relationships between several response variables and dHis supply. Across studies, His supplementation increased plasma His concentration (SMD = 1.39; 95% CI: 1.17–1.61), as well as DMI (SMD = 0.240; 95% CI: 0.051–0.429) and milk yield (MY; SMD = 0.667; 95% CI: 0.468–0.866), respectively. Further, milk true protein concentration (MTP; SMD = 0.236; 95% CI: 0.046–0.425) and milk true protein yield (MTPY; SMD = 0.581; 95% CI: 0.387–0.776) were increased by His supplementation. Notably, the increase in MTP concentration and MTPY were 3.9 and 1.3 times greater for studies with MP-deficient (according to NRC 2001) diets compared with studies with MP-adequate diets. The regression analyses revealed that production parameters (DMI, MY, and MTPY) responded in a nonlinear manner to increasing His supply. Further, we detected a difference in the magnitude of change in MTPY and plasma His concentration with the level of His supply and between His supplementation methods, being greater for infused His compared with RPHis. Lastly, a linear and negative relationship between Eff His and the ratio of total digestible His to net energy for lactation supply was observed, indicating an important interaction between dHis and energy supply and Eff His (i.e., utilization of dHis to support protein export). Overall, these analyses confirm His as an important AA in dairy cattle nutrition. [ABSTRACT FROM AUTHOR]

Many farms document daily milk yields of individual cows because these are a good indicator of cow well-being. It is established that extreme meteorological conditions influence the milk yields by causing heat and cold stress, whereas less is known about the effects of moderate changes in meteorological conditions. Thus, the aim of the present study was to evaluate whether individual daily milk yield predictions can be improved by considering such changes. We evaluated 8 years of milking and meteorological data from Eastern Switzerland with a total of 33,938 daily milkings from 145 Brown Swiss and 64 Swiss Fleckvieh cows. The cows were aged between 1.9 and 13.5 years at parturition. The data set was split into 7 periods according to the days in milk (DIM) and subsequently filtered into subsets by breed and parity. We applied Gaussian process regression to predict individual daily milk yield. We compared different models including DIM, lagged milk yield, and meteorological variables as features and found that models including the lagged milk yield performed best. Within the period of 5 to 90 DIM, we were able to predict individual next-day milk yield from the cow's last milkings with a root mean squared error (RMSE) of 2.1 kg. In contrast, without information on the previous milk yield, accuracy of milk yield prediction was lower, with an RMSE close to 8 kg. The models holding information about previous milk yields showed a substantial increase in performance. Within a more homogeneous data subset filtered by breed or parity or both, predictions were even better, with a relative RMSE of 4.3% for first-parity Fleckvieh cows. However, we found that including meteorological features, such as temperature, rainfall, wind speed, temperature humidity index, cooling degree, and barometric pressure, did not improve the predictions in any of the evaluated periods. This finding indicates that considering meteorological features in daily milk yield prediction models is not useful in moderate climates; considering lagged milk yield is sufficient. We hypothesize that this meteorological information, among other influences, is indirectly contained in the lagged milk yield. [ABSTRACT FROM AUTHOR]

The greenhouse gas emission intensity of US milk production (i.e., greenhouse gas emissions per unit of production) has varied across time and states. However, research has not examined how farm-sector trends affect the state-level emission intensity of production. We estimated fixed effects regressions with state-level panel data from 1992 through 2017 to test how US dairy farm-sector changes influenced the greenhouse gas emission intensity of production. We found that increases in per cow milk productivity reduced the enteric greenhouse gas emission intensity of milk production, while it had no statistically significant effect on the manure greenhouse gas emission intensity of production. In contrast, increases in average farm size and the number of farms reduced the manure greenhouse gas emission intensity of milk production, while they did not affect the enteric greenhouse gas emission intensity of production. [ABSTRACT FROM AUTHOR]

Some cellulolytic bacteria require 1 or more branched-chain volatile fatty acids (BCVFA) for the synthesis of branched-chain AA and branched-chain long-chain fatty acids because they are not able to uptake branched-chain AA or lack 1 or more enzymes to synthesize branched-chain AA de novo. Supplemental BCVFA and valerate were included previously as a feed additive that was later removed from the market; these older studies and more current studies have noted improvements in neutral detergent fiber digestibility and milk efficiency. However, most studies provided a single BCVFA or else isobutyrate (IB), 2-methylbutyrate (MB), isovalerate, and valerate altogether without exploring optimal combinations. Our objective was to determine a combination of isoacids that is optimal for milk production. Sixty (28 primiparous and 32 multiparous) lactating Jersey cows (106 ± 54 days in milk) were blocked and assigned randomly to either a control (CON) treatment without any isoacids, MB [12.3 mmol/kg dry matter (DM)], MB + IB (7.7 and 12.6 mmol/kg DM of MB and IB, respectively), or all 4 isoacids (6.2, 7.3, 4.2, and 5.1 mmol/kg DM of MB, IB, isovalerate, and valerate, respectively). Cattle were fed the CON treatment for a 2-wk period, then were assigned randomly within a block to treatments for 8 wk (n = 15). There was a trend for an interaction of supplement and parity for milk components. There were no differences in components for primiparous cows, whereas MB + IB tended to increase protein concentration by 0.04 and 0.08 percentage units in multiparous cows compared with the CON and MB treatments, respectively. Feeding MB + IB increased fat concentration by 0.23 to 0.31 percentage units compared with all other treatments in multiparous cows. Milk yield and dry matter intake (DMI) did not change with treatment. Treatment interacted with week for milk net energy for lactation/DMI; MB + IB tended to increase milk net energy of lactation/DMI by 0.10 Mcal/kg compared with MB and approached a trend for CON, mainly during the early weeks of the treatment period, whereas differences decreased during the last 2 wk of the treatment period. Cows fed MB had the highest 15:0 anteiso fatty acids in the total milk fatty acid profile, which was greater than that for CON or MB + IB cows, but not cows supplemented with isoacids. Cows fed MB alone had the numerically lowest milk net energy for lactation/DMI. The combination of MB + IB appeared optimal for increasing feed efficiency in our study and was not at the expense of average daily gain. Further research is needed for evaluating how potential changes in supplemental isoacid dosage should vary under differing dietary conditions. [ABSTRACT FROM AUTHOR]

A network meta-analysis was conducted to determine the effects of feeding feed-grade urea (FGU) or slow-release urea (SRU) as a replacement for true protein supplements (control; CTR) in high-producing dairy cattle diets. Research papers were selected (n = 44) from experiments published between 1971 and 2021 based on the following criteria: dairy breed, detailed description of the isonitrogenous diets fed, provision of FGU or SRU (or both), high-yielding cows (>25 kg/cow per day), and results that included at least milk yield and composition, but data on nutrient intake, digestibility, ruminal fermentation profile, and N utilization were also considered. Most studies compared only 2 treatments, and a network meta-analysis approach was adopted to compare the effects among CTR, FGU, and SRU. Data were analyzed using a generalized linear mixed model network meta-analysis. Forest plots of milk yield were used to visualize the estimated effect size of treatments. Cows included in the study produced 32.9 ± 5.7 L/d of milk, 3.46 ± 5.0% of fat, and 3.11 ± 0.2% of protein with an intake of 22.1 ± 3.45 kg of dry matter. Average diet composition was 1.65 ± 0.07 Mcal of net energy for lactation, 16.4 ± 1.45% CP, 30.8 ± 5.91% neutral detergent fiber, and 23.0 ± 4.62% starch. Average supply of FGU was 209 g/cow per day, whereas the average supply of SRU was 204 g/cow per day. With some exceptions, feeding FGU and SRU did not affect nutrient intake and digestibility, N utilization, and milk yield and composition. However, the FGU reduced the acetate proportion (61.6 vs. 59.7 mol/100 mol) and the SRU reduced the butyrate proportion (12.4 vs. 11.9 mol/100 mol) compared with CTR. Ruminal ammonia-N concentration increased from 8.47 to 11.5 and 9.3 mg/dL in CTR, FGU, and SRU, respectively. Urinary nitrogen excretion increased from 171 to 198 g/d in CTR versus the 2 urea treatments, respectively. The use of moderate doses of FGU in high-producing dairy cows may be justified based on its lower cost. [ABSTRACT FROM AUTHOR]

Heat tolerance is a key feature of resilient animals. Offspring of animals that suffer environmental stress during pregnancy could show physiological, morphological, and metabolic modifications. This is due to a dynamic reprogramming of the epigenetics of the mammalian genome that occurs in the early life cycle. Thus, the aim of this study was to investigate the extent of the transgenerational effect of heat stress during the pregnancy of Italian Simmental cows. The effects of dam and granddam birth months (as indicator of pregnancy period) on their daughter and granddaughter estimated breeding values (EBV) for some dairy traits as well as of the temperature-humidity index (THI) during the pregnancy were tested. A total of 128,437 EBV (milk, fat, and protein yields, and somatic cell score) were provided by the Italian Association of Simmental Breeders. The best birth months (of both dam and granddam) for milk yield and protein yield were May and June, whereas the worst were January and March. Great-granddam pregnancies developed during the winter and spring seasons positively affected the EBV for milk and protein yields of their great-granddaughters; in contrast, pregnancies during summer and autumn had negative effects. These findings were confirmed by the effects of maximum and minimum THI in different parts of the great-granddam pregnancy on the performances of their great-granddaughters. Thus, a negative effect of high temperatures during the pregnancy of female ancestors was observed. Results of the present study suggest a transgenerational epigenetic inheritance in Italian Simmental cattle due to environmental stressors. [ABSTRACT FROM AUTHOR]

Extending the voluntary waiting period (VWP) for primiparous cows can have a positive impact on fertility without a negative impact on milk production per day in the calving interval (CInt). We investigated the effect of extended VWP during first lactation on milk yield (MY) during 2 consecutive lactations in primiparous cows. The study involved 16 commercial herds in southern Sweden. A total of 533 Holstein and Red dairy cattle (Swedish Red, Danish Red, Ayrshire) dairy cows were randomly assigned to a conventional 25 to 95 d VWP (n = 252) or extended 145 to 215 d VWP (n = 281). Data on calvings, inseminations, and test-day yields were retrieved from the Swedish Milk Recording System. Cows with VWP according to plan and completing 1 or 2 CInt with a second or third calving were included in the data analysis. Whole lactation and 305-d energy-corrected milk (ECM) yield were higher for the extended VWP group than the conventional VWP group in both the first lactation (12,307 vs. 9,587 and 9,653 vs. 9,127 kg ECM) and second lactation (12,817 vs. 11,986 and 11,957 vs. 11,304 kg ECM). We found no difference between the VWP groups in MY per day during the first CInt or during the first and second CInt combined, although MY per day during the second CInt was around 1.5 kg higher for cows with extended VWP than for cows with conventional VWP. Thus extended VWP for primiparous cows can be used as a management tool without compromising MY. [ABSTRACT FROM AUTHOR]

From an initial data set involving 84,189 lactations, this research evaluated the relationship between dry period length (DPL) and milk production, culling risk, and fertility. The data set included a total of 48,297 multiparous cow lactation records, with a calving event occurring in 2019 and 2020, belonging to 62 Italian herds with at least 150 cows. The DPL was classified into 5 categories (<40, 40–49, 50–60, 61–70, and >70 d) and these categories were used to establish the association between DPL and the outcome variables. All data obtained were assessed with simple and multiple linear regressions and Cox proportional hazard models. Cumulative milk production at 60 d in milk (DIM) was the highest in DPL categories of 61 to 70 d (2,480.29 kg/cow) and 50 to 60 d (2,474.39 kg/cow), and the lowest in <40 d (2,281.29 kg/cow). Similarly, DPL categories 61 to 70 d (10,830.94. kg/cow) and 50 to 60 d (10,817.48 kg/cow) had the highest 305-d milk production, whereas the <40 d (10,200.96 kg/cow) had the lowest one. The groups with a DPL of 40 to 49 d and >70 d had slightly, but significant, lower milk production both as cumulative 60 DIM and predicted 305-d milk production. Culling risk had a curvilinear behavior, with DPL <40 d and DPL >70 d showing significantly higher odds for culling during the first 60 DIM compared with DPL of 50 to 60 d [relative risk (RR): 1.53; RR: 1.46]. Within the same comparison, DPL of 61 to 70 d also had a slightly higher risk for culling (RR: 1.13). The DPL was associated also with fertility, with DPL of 40 to 49 d and 50 to 60 d having the greatest odds for pregnancy within the first 200 DIM. The DPL of <40, 61 to 70, and >70 d were negatively associated with fertility and showed pregnancy risks of 0.87, 0.95, and 0.94, respectively. This paper reinforces the importance of DPL as we demonstrated its association with milk production, culling, and fertility. Despite being attractive for high production dairy cows, very short dry periods are at the same time also associated with higher culling risk, lower milk production and fertility. Long DPL is detrimental, especially regarding culling and fertility. In summary, reducing variability in DPL and avoiding extremes by improving reproductive performance, maximizing late lactation milk production and making wise decisions on dry-off timing, may lead to better performances and lower early culling under Italian dairy conditions. [ABSTRACT FROM AUTHOR]

Yeast culture and phytonutrients are dietary supplements with distinct modes of action, and they may have additive effects on the performance of dairy cattle. The objective of this study was to investigate the effects of a preparation of phytonutrients and a yeast culture from Saccharomyces cerevisiae on lactational performance, total-tract digestibility of nutrients, urinary nitrogen losses, energy metabolism markers, and blood cells in dairy cows. Thirty-six mid-lactation Holstein cows (10 primiparous and 26 multiparous) were used in an 8-wk randomized complete block design experiment with a 2-wk covariate period, 2 wk for adaptation to the diets, and a 4-wk experimental period for data and samples collection. Following a 2-wk covariate period, cows were blocked by days in milk, parity, and milk yield and randomly assigned to 1 of 3 treatments (12 cows per treatment): basal diet supplemented with 14 g/cow per day yeast culture (YC; S. cerevisiae), basal diet supplemented with 1.0 g/cow per day phytonutrients (PN; 5.5% cinnamaldehyde, 9.5% eugenol, and 3.5% capsicum oleoresin), or basal diet supplemented with a combination of YC and PN (YCPN). Treatments were top-dressed once daily on the total mixed ration at time of feeding. Dry matter intake, milk yield, and feed efficiency were not affected by treatments. Milk composition and energy-corrected milk yield were also not affected by supplementation of YC, PN, and YCPN. There were no differences in intake or total-tract digestibility of dietary nutrients among treatments. Compared with YC, the PN and YCPN treatments tended to decrease the proportion of short-chain fatty acids in milk fat. There was an additive effect of YC and PN supplementation on urinary urea nitrogen (UUN) excretion relative to total nitrogen intake. Cows fed a diet supplemented with YCPN had lower UUN excretion than cows in YC and tended to have lower UUN excretion compared with PN. Blood monocytes count and percentage were decreased in cows fed PN and YCPN diets compared with YC. Treatments did not affect concentrations of blood β-hydroxybutyrate and total fatty acids. Overall, lactational performance, digestibility of nutrients, energy metabolism markers, and blood cells were not affected by YC, PN, or YCPN supplementation. A combination of PN and YC had an additive effect on nitrogen excretion in dairy cows. [ABSTRACT FROM AUTHOR]

Increasing the productivity of Canadian dairy goats is critical to the competitiveness of the sector; however, little is known about the underlying genetic architecture of economically important traits in these populations. Consequently, the objectives of this study were as follows: (1) to perform a single-step GWAS for milk production traits (milk, protein, and fat yields, and protein and fat percentages in first and later lactations) and conformation traits (body capacity, dairy character, feet and legs, fore udder, general appearance, rear udder, suspensory ligament, and teats) in the Canadian Alpine and Saanen breeds; and (2) to identify positional and functional candidate genes related to these traits. The data available for analysis included 305-d milk production records for 6,409 Alpine and 3,434 Saanen does in first lactation and 5,827 Alpine and 2,632 Saanen does in later lactations; as well as linear type conformation records for 5,158 Alpine and 2,342 Saanen does. Genotypes were available for 833 Alpine and 874 Saanen animals. Both single-breed and multiple-breed GWAS were performed using single-trait animal models. Positional and functional candidate genes were then identified in downstream analyses. The GWAS identified 189 unique SNP that were significant at the chromosomal level, corresponding to 271 unique positional candidate genes within 50 kb up- and downstream, across breeds and traits. This study provides evidence for the economic importance of several candidate genes (e.g., CSN1S1 , CSN2 , CSN1S2 , CSN3 , DGAT1 , and ZNF16) in the Canadian Alpine and Saanen populations that have been previously reported in other dairy goat populations. Moreover, several novel positional and functional candidate genes (e.g., RPL8 , DCK , and MOB1B) were also identified. Overall, the results of this study have provided greater insight into the genetic architecture of milk production and conformation traits in the Canadian Alpine and Saanen populations. Greater understanding of these traits will help to improve dairy goat breeding programs. [ABSTRACT FROM AUTHOR]

The social environment experienced by livestock can have implications for their health, welfare, and subsequently, their productivity. Changes in the dairy industry have led to larger herd sizes and altered management of cows, which has impacted their social environment. Studies have shown that mixing of animals can lead to social instability of groups and expansion of herds can lead to high stocking densities resulting in social stress and negative effects on production. Yet few studies have assessed the putative impact of positive cow-cow interactions, such as proximity to preferred herd mates and engaging in grooming, on milk production and udder health. To address this, we used cattle proximity as a proxy for affiliative interactions between cows in three dairy herds in south-west England over one week study periods. We created proximity networks of dairy cows and measured cow-cow associations according to milk yield, somatic cell count (SCC; an indicator of mastitis), parity (number of lactations in the cow's lifetime), and lactation stage (grouped by days in milk for current lactation). We then assessed associations between social factors and production and health measures (milk yield and SCC). In all three herds, cows interacted more with cows in the same parity, suggesting early social bonding may be evident later in life and that grouping animals in terms of parity might encourage affiliative interactions. Cows did not associate according to milk yield, SCC, or lactation stage. There was no significant association between milk production or SCC and the total time spent in social contact with other cows, the mean time spent with the four closest herd mates, or the number of closest herd mates of the same parity. We suggest that further research on positive social environments for dairy cattle is warranted in the interests of improving welfare and enabling a more robust assessment of the putative effects on production and health parameters • No significant link between milk yield or SCC and time spent near other cows. • No significant link between milk yield or SCC and time spent near preferred cows. • No significant link between milk yield or SCC and time spent near same-parity cows. • Dairy cows preferred to spend time close to conspecifics of the same parity. [ABSTRACT FROM AUTHOR]

• Does feeding aging corn affect milk production and health of dairy cows? • Does feeding fermented aging corn improve the milk performance of dairy cows? • Aging corn did not affect the performance but decreased the antioxidant capacity. • Fermented aging corn was beneficial to milk performance and the overall health. • Fermentation may improve the utilisation of non-conventional feed resources. Aging reduces the nutritional value of corn grain, which may be improved by fermentation prior to use. This study investigated the effects of replacing conventional corn (CC) with aging corn (AC) and fermented aging corn (FAC) in the diets of lactating Holstein cows. Six healthy third-parity Holstein cows were used in a replicated 3 × 3 Latin square experiment with 21-day periods. Cows were fed twice and milked twice daily. The cows were randomly divided into three treatment groups: (1) CC diet: a diet with 23.6% starch in diet DM containing 24.0% conventional corn; (2) AC diet: a diet with 23.5% starch in diet DM containing 24.0% aging corn replacing conventional corn; and (3) FAC diet: a diet with 23.2% starch in diet DM containing 24.6% fermented aging corn replacing conventional corn. The diets were formulated to be isonitrogenous and contained identical roughage. The FAC treatment increased the starch digestibility compared with AC. Feeding FAC increased the concentrations of total volatile fatty acid compared with CC and AC and decreased the molar proportion of acetate compared with AC. At the family level, the relative abundance of Prevotellaceae was higher on FAC than CC. The relative abundance of Succinivibrionaceae was lower on FAC than on CC and AC. Besides, at the genera level, the relative abundance of Succinivibrionaceae_UCG_002 in the rumen was higher on AC than CC and FAC. The relative abundance of Prevotella and Ruminococcus was higher on FAC than CC and AC. The relative abundance of Succinivibrionaceae_UCG_001 was lower on FAC than CC. The Simpson index was lower on FAC than CC and AC. The FAC treatment increased the milk yield (34.0, 33.7, and 35.2 kg/d for CC, AC, and FAC group, respectively) and protein yield, and thus, energy-corrected milk production was increased, and at the same time, decreased the somatic cell score compared with CC and AC. The AC treatment increased the malondialdehyde concentration in plasma compared with CC and FAC. The concentrations in plasma of triglyceride and malondialdehyde were lower on FAC than AC. The immunoglobulin G concentration in plasma was higher on FAC than CC and AC. Overall, feeding AC resulted in decreased plasma antioxidant capacity compared with CC, whereas feeding FAC altered the relative abundance of bacteria in the rumen and improved starch digestibility, ruminal bacterial diversity, lactation performance, plasma antioxidant capacity and immune competence compared with AC in dairy cows. [ABSTRACT FROM AUTHOR]

Hyperinsulinemia concurrent with hypoglycemia is one of a myriad of physiological changes typically experienced by lactating dairy cows exposed to heat stress, the consequences of which are not yet well defined or understood. Therefore, the objective of this experiment was to separate the production-related effects of hyperinsulinemia with hypoglycemia from those of a hyperthermic environment. Multiparous lactating Holstein cows (n = 23; 58 ± 4 d in milk, 3.1 ± 0.3 lactations) were housed in temperature-controlled rooms and all were subjected to 4 experimental periods as follows: (1) thermoneutral (TN; temperature-humidity index of 65.1 ± 0.2; d 1–5), (2) TN + hyperinsulinemic-hypoglycemic clamp (HHC; insulin infused at 0.3 µg/kg of BW per h, glucose infused to maintain 90 ± 10% of baseline blood glucose for 96 h; d 6–10), (3) heat stress (HS; temperature-humidity index of 72.5 ± 0.2; d 16–20), and (4) HS + euglycemic clamp (EC; glucose infused to reach 100 ± 10% of TN baseline blood glucose for 96 h; d 21–25). Cows were fed and milked twice daily. Feed refusals were collected once daily for calculation of daily dry matter intake, and milk samples were collected at the beginning and end of each period for component analyses. Circulating insulin concentrations were measured in daily blood samples, whereas glucose concentrations were measured more frequently and variably in association with clamp procedures. Rectal temperatures and respiration rates were greater during HS than TN, as expected, and states of hyperinsulinemia and hypoglycemia were successfully induced by the HHC and high ambient temperatures (HS and EC). Feed intake differed based upon thermal environment as it was similar during TN and HHC periods, and declined for HS and EC. Milk production was not entirely reflective of feed intake as it was greatest during TN, intermediate during HHC, and lowest during HS and EC. All milk components differed with the experimental period, primarily in response to the thermal environment. Interestingly, TN baseline glucose concentrations were highly correlated with the change in glucose from TN to HS, and were related to glycemic status during HS. Furthermore, although few in number, those cows that failed to become hypoglycemic during HS tended to have a greater reduction in milk yield. The work presented here addresses a critical knowledge gap by broadening our understanding of the physiological response to heat stress and the related changes in glycemic state. This broadened understanding is fundamental for the development of novel, innovative management strategies as the dairy industry is compelled to become increasingly efficient in spite of global warming. [ABSTRACT FROM AUTHOR]

Heat stress has negative consequences for milk production and reproduction of dairy cattle. These adverse effects are likely to increase because of climate change and anticipated increases in milk yield. Some of the variation among cows in ability to resist effects of heat stress is genetic. The current objective of this observational study was to assess the effectiveness of the Australian breeding value for heat tolerance (ABVHT) based on the decline in milk yield with heat stress for predicting cow differences in effects of heat stress on regulation of body temperature, milk production, and reproductive function. Genomic breeding values for heat tolerance were calculated for 12,487 cows from a single California dairy farm. Rectal temperature in the afternoon (1100–2045 h) was measured on a subset of 626 lactating cows with ABVHT ≥102 (heat tolerant) or <102 (heat sensitive). Rectal temperature was 0.12°C lower for heat-tolerant cows than heat-sensitive cows. Vaginal temperatures were measured every 15 min for 5 d in 118 cows with ABVHT ≥108 (extreme heat tolerant) or <97 (extreme heat sensitive). Vaginal temperature was 0.07°C lower for extreme heat–tolerant cows than extreme heat–sensitive cows. Lactation records for 4,703 cows with ABVHT were used to evaluate seasonal variation in first 90-d milk yield, fat percent, and protein percent for each ABVHT quartile. Overall, cows with higher ABVHT had lower milk yield, fat percentage, and protein percentage and higher first service pregnancy rate. There was no summer depression in production or reproduction or interactions between season and ABVHT quartile. We observed that ABVHT can successfully identify heat-tolerant cows that maintain lower body temperatures during heat stress. The lack of a pronounced seasonality in milk production or reproduction precluded evaluation of whether ABVHT is related to the magnitude of effect of heat stress on those traits. [ABSTRACT FROM AUTHOR]

The objective of this study was to investigate the effects of an exogenous enzyme preparation from Aspergillus oryzae and Aspergillus niger on lactational performance of dairy cows. Forty-eight Holstein cows (32 primiparous and 16 multiparous) averaging (± SD) 36.3 ± 8.7 kg/d milk yield and 141 ± 52 d in milk were enrolled in a 10-wk randomized complete block design experiment (total of 24 blocks) and assigned to 1 of 2 treatments: basal diet, no enzyme supplementation (CON) or the basal diet supplemented with 4.2 g/kg dry matter intake (DMI) of an exogenous enzyme preparation containing amylolytic and fibrolytic activities (ENZ). After a 2-wk covariate period, premixes with the enzyme preparation or control were top-dressed daily by mixing with approximately 500 g of total mixed ration. Production data were collected daily and averaged by week. Milk samples were collected every other week, and milk composition was averaged by week. Blood, fecal, and urine samples were collected over 2 consecutive days at 0, 4, 8, 12, and 36 h after feeding during the last week of the experiment. Compared with CON, cows fed ENZ tended to increase DMI and had increased milk concentrations of true protein, lactose, and other solids. Milk fat content tended to be higher in CON cows. A treatment × parity interaction was found for some of the production variables. Primiparous cows receiving ENZ had greater yields of milk, energy-corrected milk, milk true protein, and lactose compared with CON primiparous cows; these production variables did not differ between treatments for multiparous cows. Intake and total-tract digestibility of nutrients did not differ between treatments. Concentrations of blood glucose and total fatty acids were not affected by ENZ supplementation, but β-hydroxybutyrate concentration tended to be greater in ENZ cows. Overall, the exogenous enzyme preparation used in this study increased milk protein and lactose concentrations in all cows, and milk production in primiparous but not multiparous cows. The differential production response between primiparous and multiparous cows was likely a result of a greater increase in DMI with ENZ supplementation in the younger animals. [ABSTRACT FROM AUTHOR]

To facilitate breeding for improved resistance to the reproductive disorder of retained placenta (RP), genetic parameters were estimated for RP and its genetic correlation with other reproductive disorders as well as with production and fertility traits of Iranian Holstein dairy cows. Data were 154,048 lactation records collected between 2011 and 2018 from 59,610 Holstein dairy cows in 9 Iranian herds. Other reproductive disorders included dystocia, stillbirth, and twinning. Fertility records were available for days from calving to first service (DFS), days open (DO), number of inseminations per conception (NIC), and success of first insemination (SFI). Genetic parameters for RP were estimated using univariate linear and logistic animal models with ASREML software. The univariate linear animal model was used to implement bivariate analysis to investigate potential genetic correlations of RP with other reproductive disorders and with production and fertility traits. Heritability estimates for RP were low from both linear (0.031) and logistic (0.092) animal models. Estimated genetic correlations with RP were −0.04 for twinning, 0.32 for stillbirth, and 0.34 for dystocia, which indicates that selection against RP could indirectly select against dystocia and stillbirth. Estimated genetic correlations between RP and production traits (milk, fat, and protein yields) at 100, 200, and 305 d in milk ranged from −0.12 to −0.29; the greatest correlation (−0.29) was for the first 100 d in milk. A moderate positive genetic correlation (0.25) was found for RP and DO, DFS, and NIC, whereas a low negative genetic correlation (−0.09) was found between RP and SFI. The pedigree-based genetic analysis of RP showed that this trait has a low heritability, is linked to other reproductive disorders, and generally has an unfavorable relationship with production and fertility traits. Selection against RP can reduce the incidence of reproductive disorders and improve fertility and production traits. • Heritability estimates for retained placenta (RP) was less than 0.1. Although in the logistics model it was three times as much as the linear model. • The estimated genetic correlation between RP and dystocia and stillbirth were moderately positive. • The genetic correlations between RP with milk components in different days in milk were moderately negative. • Days open, days from calving to first service had a moderately positive genetic correlation with RP. • Selection against dystocia and stillbirth can reduce the incidence of RP in dairy cows and improve reproductive performance. • The estimated genetic correlation between RP and success in first service was negative and less than 0.1. [ABSTRACT FROM AUTHOR]

The objective of this experiment was to compare the effects of calcareous marine algae (CMA; Acid Buf, Celtic Sea Minerals) with a limestone-based control on feed intake, milk production, energy balance, serum mineral metabolites, and inflammatory markers in transition dairy cows. Twenty-two multiparous and 10 primiparous cows were assigned to 2 treatments from 25 d before expected parturition until 42 d postpartum. Cows were assigned to treatment according to a randomized complete block design based on parity, pre-experimental body condition score, previous 305-d milk yield, and either fat + protein yield (for multiparous cows) or predicted transmitting ability for milk yield and fat + protein yield (for primiparous cows). Cows were fed a negative dietary cation-anion difference [−50 mEq/kg] total mixed ration (TMR) based on corn silage, grass silage, and straw during the prepartum period and a 50:50 forage:concentrate TMR based on grass silage, corn silage, and concentrate during the postpartum period. The 2 dietary treatments consisted of a control (CON), which contained limestone as the primary calcium source, and CMA, in which limestone was replaced by CMA at 0.42% and 0.47% of dry matter for the pre- and postpartum periods, respectively. The dietary treatments were fed as 2 different concentrate pellets added to the TMR. Cows fed the CMA diet had higher dry matter intake in both the prepartum (+1.08 kg) and postpartum (+0.94 kg) periods compared with cows fed the CON diet. Fat yield (+0.11 kg), fat concentration (+0.43%), and 4% fat-corrected milk (+1.56 kg) were higher in cows fed CMA than in cows fed CON. The concentration of plasma serum amyloid A was reduced and that of serum P was increased on the CMA treatment compared with the CON treatment. These findings demonstrate the benefits of supplementing CMA to dairy cows during the transition period compared with a CON treatment containing limestone as the primary Ca source. [ABSTRACT FROM AUTHOR]

To overcome the environmental challenges faced by the global agricultural sector while also ensuring economic viability, dairy farmers must improve the efficiency of their systems. To improve system efficiency, the performance of an average production system must be determined, as it establishes a benchmark from which the efficacy of proposed management practices and mitigation strategies can be assessed. Identified management practices and mitigation strategies can then be compiled to create ambitious but realistic targets for the sector to strive toward. Therefore the objective of this study was to calculate the environmental performance of an average spring-calving pasture-based dairy system and an ambitious target dairy system. Life cycle assessment (LCA) of 2 pasture-based dairy systems were conducted: (1) current average spring-calving pasture-based dairy system (current), and (2) a spring-calving pasture-based dairy system that has achieved key performance targets set by the most efficient dairy systems (target). An existing dairy LCA model was updated with country-specific emission factors, life cycle inventory data, and recommended methodologies. The environmental impact categories assessed were global warming potential, nonrenewable energy depletion, acidification potential, and eutrophication potential (marine and freshwater). Two functional units were used: per kilogram of fat- and protein-corrected milk (FPCM), and per hectare. To assess the effects of the model updates, the current dairy system was simulated twice, once with the previous version of the dairy LCA model, and second with the updated LCA model. The addition of country-specific emission factors, updated inventory data, and implementation of recommended methods has resulted in global warming potential and nonrenewable energy depletion being reduced by 10.4% and 10.9%, respectively. The updates had negligible effects on acidification and eutrophication potential. The inclusion of assumptions around carbon sequestration in grassland further reduced global warming potential by 16.4%. Moving from the current dairy system to the target dairy system was reported to reduce the environmental impact per kilogram of FPCM across all impact categories investigated. When expressed per hectare, transitioning toward the target dairy system reduced acidification, freshwater eutrophication, and nonrenewable energy depletion by 2.0%, 8.8%, and 13.8%, respectively. In contrast, transitioning toward the target dairy system increased global warming per hectare and, to a lesser degree, marine eutrophication potential per hectare. The increase in global warming and marine eutrophication potential per hectare was attributed to the increase in stocking rate and subsequently milk production per hectare (9,950 vs. 14,100 kg of FPCM/ha). This study demonstrates that the adoption of management practices that improve system efficiency will reduce the environmental impact per kilogram of FPCM and can contribute to the future sustainability of pasture-based dairy systems. However, improved system efficiency can be offset by the associated increase in productivity, highlighting the importance of reporting multiple environmental impact categories and functional units to prevent pollution swapping. New research and mitigation strategies will be required to improve the environmental sustainability of dairy systems beyond the target system in the future. [ABSTRACT FROM AUTHOR]

Poor udder health status can have a detrimental effect on milk yield and reproductive performance, leading to reductions in the dairy farm profit. The objective of this retrospective longitudinal study was to assess the associations of somatic cell count (SCC) with daily milk yield and reproductive performance. A database with 1,930,376 lactations from 867 Argentinean grazing dairy herds records collected for 14 years was used. The association of the evolution of SCC (healthy vs. new case vs. cured vs. chronic; with 150,000 SCC/mL as threshold) and of the severity of SCC [mild (150,000-–400,000 SCC/mL) vs. moderate (400,000–1,000,000 SCC/mL) vs. severe (>1,000,000 SCC/mL)] with the odds for conception were estimated. Finally, the associations of the linear score of SCC (LS-SCC) with daily milk yield were estimated depending on parity and milk production quartile. The odds ratios (CI 95%) for conception at first service were 0.921 (0.902–0.941), 0.866 (0.848–0.884), and 0.842 (0.826–0.859) for the new case, cured, and chronic cows compared with healthy cows, respectively. Also, the odds ratios (CI 95%) for conception were 0.902 (0.881–0.925), 0.837 (0.808–0.866) and 0.709 (0.683–0.736) for mild, moderate and severe cases compared with healthy cows, respectively. An increase of one point of LS-SCC was associated with decreases of 0.349, 0.539, and 0.676 kg in daily milk yield for first-, second-, and third-lactation cows, respectively. In conclusion, SCC is negatively associated with the risk for conception and with daily milk yield in grazing dairy cows. This negative relationship with conception is higher when SCC increase occurs after the service date and it is influenced by severity of mastitis, and in the case of milk yield, the negative association is influenced by parity, milk production quartile, and severity of mastitis. [ABSTRACT FROM AUTHOR]

Genetic selection is an important method to enhance productive traits in local sheep through crossbreeding and selection programs. The objectives of this study were to estimate the genetic parameters of total milk yield (MY) and lactation period (LP), and to investigate the association between the estimated breeding values of milk yield with 50 K SNP chip results in Awassi sheep. Heritability and repeatability estimates were 0.19 and 0.317 for MY and 0.085 and 0.163 for LP, respectively. The Genomic scan covered 42,478 SNPs and revealed two candidate loci (s244475780.1 and s51470.1) that significantly affect milk production, located on Spermatogenesis-Associated Protein6 (SPATA6) and Galactose-3-O-Sulfotransferase 3 (GAL3ST3) genes. The genotype frequencies for the SPATA6 gene variant were 0.0566 for AA, 0.4528 for AG, and 0.4906 for AA, with allele frequency of 0.283 for A and 0.717 for G. The genotype frequencies for the GAL3ST3 gene variants were 0.07843 for TT, 0.4118 for TG, and 0.5098 for GG, with allele frequency of 0.284 for T and 0.716 for G. The two SNPs genotypes are promising biomarkers to increase milk production during genetic selection programs by reducing the frequency of G alleles in the two loci in Awassi sheep genome. [ABSTRACT FROM AUTHOR]

Our aim was to evaluate whether increasing soluble carbohydrates in the herbage by changing the time of the grazing session or including Acacia mearnsii tannin in the diet would affect intake, digestion, N partitioning, and productive performance of dairy cows fed a diet combining ryegrass herbage with partial total mixed ration (PMR). We hypothesized that both strategies could reduce the concentration of NH 3 -N in the rumen, reducing urinary N excretion. Nine Holstein cows were used in a triplicate 3 × 3 Latin square experiment with 3 experimental periods of 22 d. The cows were fed a fixed amount of PMR [60% of the predicted individual dry matter intake (DMI)], and an unrestricted amount of herbage in 1 grazing session of 5 h/d. The treatments were (1) morning grazing session and afternoon PMR meal (AM); (2) morning PMR meal and afternoon grazing session (PM); and (3) morning grazing session and afternoon PMR meal supplemented with 15.0 g of tannins/kg of PMR dry matter (TAN). Milk production was not affected by treatments. Although the protein concentration was lower for TAN than for PM, no differences were detected for the yield of any component between treatments. The concentration of individual or grouped fatty acids in milk fat was not affected by treatments, except for 16:1 cis -9 and Δ9-desaturase ratios 14:1/14:0 and 16:1/16:0, which were lower for TAN. Treatments did not affect total DMI, but PM tended to increase herbage DMI and reduce dry matter and crude protein digestibilities. Treatments did not affect cow eating and ruminating behavior except for the proportion of time spent eating PMR, which was higher for PM and TAN. Although no relevant effects of treatments on ruminal fermentation, purine derivatives excretion in urine, or N excretion in milk were detected, both PM and TAN decreased the total N excreted in urine by an average of 8% compared with AM. In conclusion, changing the grazing session from the morning to the afternoon and including tannins in the diet were effective in decreasing the excretion of urinary N but did not change the productive performance of dairy cows fed PMR and ryegrass herbage. [ABSTRACT FROM AUTHOR]

Most fat supplements added to dairy diets are derived from palm acid oil or palm fatty acid distillate. There are environmental concerns about palm oil production due to deforestation and high greenhouse gas (GHG) emissions. The objective of this study was to evaluate a palm-free fat supplement, Envirolac. Envirolac contains vegetable oils, marine oils and glycerine encapsulated within a cellulosic fibre-clay mineral carrier matrix. The carrier matrix has small particle size to facilitate rapid rumen passage and minimal interference with rumen digestion. Fifty cows were divided into two balanced groups of 25 cows. Each group received Control (calcium soap of palm fatty acid distilate, 0.5 kg/d) and Envirolac (0.5 kg/d) diets in a crossover design with two feeding periods of four weeks duration, so that each cow received both diets. Envirolac has a lower total fat concentration than the calcium soap, so the feeding rate delivered less total fat. When fed on Envirolac, cows yielded more milk 40.7 v 40.1 kg/d), energy-corrected milk (ECM; 42.9 v 41.3 kg/d) and milk components (1605 v 1514 g fat, 1239 v 1199 g protein, 1871 v 1839 g lactose, per day), and produced milk with higher concentrations of fat (40.1 v 38.6 g/kg) and protein (30.7 v 30.1 g/kg), than when fed on Control. When fed on Envirolac, cows produced milk with higher concentrations of fatty acids (FA) synthesised de novo in the mammary gland (25.5 v 23.6 g/100 g total FA), lower concentration of palmitic acid (35.5 v 37.2 g/100 g total FA), and higher concentrations of some long-chain fatty acids (C20:0, C20:1, C20:3n3, C21:0, C22:0, C22:6n3 and C23:0), than when fed on Control. There was no effect of treatment on dry matter intake (DMI; mean 23.4 kg/d), so feed efficiency was higher (1.83 v 1.76 kg ECM/kg DMI) for Envirolac than Control. There was no effect of treatment on dry matter digestibility (0.73), methane production (433 g/d), methane yield (19.3 g/kg DMI) or methane intensity (10.9 g/kg ECM). Feed carbon footprint of Envirolac was calculated to be 1028 g CO 2 eq/kg DM, which is 0.46 of the value for a calcium soap (2830 g CO 2 eq/kg DM), and reduced feed carbon footprint per kg ECM milk production by 11 %. This study demonstrates that Envirolac can replace palm-based fat supplements in dairy diets to improve feed efficiency and reduce the carbon footprint of milk production. • Envirolac is a palm-free fat supplement for dairy cows with low carbon footprint • Cows fed Envirolac produced more milk with better composition than palm-based fat. • No effect on methane emissions or feed intake, so cows were more efficient. • Envirolac reduced feed carbon footprint per litre of milk yield by 11 %. [ABSTRACT FROM AUTHOR]

This study evaluated the reproductive, productive and financial consequences of chronic Trypanosoma vivax infection in a dairy cattle herd located in a region without the cyclic vector during two years. Animals were categorized as either positive (chronically infected) or negative for T. vivax antibodies using a commercial rapid test. Additionally, serum samples from cows were analyzed for the presence of anti- Neospora caninum antibodies. Pregnancy diagnoses were performed through rectal palpation and ultrasonography after 30, 60 and every 21 days until the 144th day of pregnancy. If an abortion occurred in the final trimester, serology and cPCR were performed on calves for T. vivax and N. caninum. The breeding period, calving interval and pregnancy losses were recorded. The milk production of each animal during the 305 days of lactation was measured, and the annual financial impact of milk production was calculated using a revenue minus feed cost (RMFC) indicator. Out of 177 cows, 71.75 % were chronically infected, and 13.50 % were T. vivax -negative. No correlation (p = 0.8854) of co-infection between T. vivax and N. caninum was observed. Negative cows required fewer (p≤0.05) artificial inseminations than chronically infected ones. T. vivax was not significantly associated (p = 0.7893) with pregnancy loss up to 81 days of pregnancy. Cows chronically infected by T. vivax had 4-fold greater chance (p = 0.0280) of experiencing pregnancy loss between 82 and 144 days of gestation. Eighteen cows aborted, two were positive for T. vivax antibodies, and one for N. caninum antibodies. The calves were negative for T. vivax and N. caninum. Chronically infected cows and negative cows for T. vivax that experienced pregnancy loss (82–144 days of pregnancy) had a longer (p≤0.05) breeding period to become pregnant, and consequently a longer calving interval compared to cows that maintained pregnancy. The difference (p≤0.05) in milk production was evident when pregnancy loss occurred between 82 and 144 days of gestation in cows chronically infected by T. vivax. The RMFC indicated a negative impact of 38.2 % on the farm's annual milk revenue due to the presence of chronically infected cows. • Cows negative for T. vivax required fewer artificial inseminations. • Chronic T. vivax cows had a risk of pregnancy loss between 82 and 144 days. • Milk production was affected in chronic T. vivax cows with pregnancy loss (82–144 days). • One chronic T. vivax cow impacts milk production by $372.9/year. • Herd with chronic trypanosomosis reduced farm's annual milk revenue by 38.2 %. [ABSTRACT FROM AUTHOR]

This case report investigated the outbreak of aflatoxicosis in a dairy herd in Pakistan, which resulted in 30 abortions of 40 confirmed (75%) pregnant cows in a period of 35 days and in 18.8% depression of farm average milk production for the entire herd. The analysis of the concentrate feed of the total mixed ration (TMR), using enzyme-linked immunosorbent assay (ELISA) procedures from two different local laboratories, indicated concentrations of 60 μg/kg dry matter (DM) of aflatoxin B1 (AFB1) and 100 μg/kg DM of total aflatoxins (AFs: sum of B1, B2, G1 and G2). Subsequently, a confirmatory analysis with a more sensitive and validated multi-metabolite liquid chromatography-tandem mass spectrometric (LC-MS/MS) method was performed. This analysis detected a concentration of total AFs in the TMR of 166 μg/kg DM ± 3.5 (AFB1:134, AFB2:17.4 and AFM1:14.9 μg/kg DM). The concentrate feed (55% of the TMR DM) was confirmed as a source of contamination, presenting a concentration >29 times higher than the EU-maximum limit value (5.68 μg/kg DM). Additionally, the multi-mycotoxin analysis evidenced the co-occurrence of 81 other toxic and potentially toxic fungal metabolites in the fed TMR. After replacing the contaminated concentrate feed with feedstuffs of the same formulation but from a new charge of ingredients, the abortion episodes ceased, and milk production increased significantly. In conclusion, the data of this case report suggest that AFs may be associated with pregnancy losses in dairy cattle and milk production depression. From the public health perspective, the data also indicate the need for a more careful examination of dairy animal feed in Pakistan. Since the high concentration of AFB1 detected in feed and considering the literature-reported transfer rates (1–6%) of this toxin to AFM1 (carcinogen for humans) in milk, the milk produced during the outbreak period is expected to be contaminated with AFM1, which raises public health concerns. [Display omitted] • Aflatoxicosis outbreak in a Pakistani dairy herd led to a 75% abortion rate and an 18.8% decrease in milk yield. • The concentrate feed was identified as the primary source of AFB1, exceeding EU limits by 29 times. • Multitarget LC-MS/MS was employed to accurately quantify mycotoxins' concentrations in the feed. [ABSTRACT FROM AUTHOR]

Efforts to mitigate enteric methane (CH 4) emission from ruminants by using the red macroalgae Asparagopsis taxiformis (AT) have demonstrated promising results both in vitro and in vivo. We assessed the effects of wild harvested and freeze-dried AT inclusion in the grass silage-based diets of Norwegian Red dairy cows on feed intake, milk yield and composition, rumen fermentation and CH 4 emission. Fifteen (9 rumen cannulated and 6 intact) multiparous cows with an average (±SD) covariate period milk yield (MY) of 33.0 (3.8) kg/day were used in the experiment. The cows were divided into three groups (n = 5) after blocking for cannulation, and initial MY. After feeding on a common diet for 21 days (i.e., Covariate period), the groups were randomly allocated to three treatments: Control (no seaweed), 0.125%AT (Control + 0.125%AT, on organic matter (OM) basis) and 0.25%AT (Control + 0.25%AT, on OM basis). The cows were adapted to their diets for 13 days, followed by 39 experimental days for data collection. Inclusion of AT at 0.125% level did not affect dry matter intake (DMI, kg/d) but signicantly reduced both MY and energy corrected milk yield (ECM, kg/d) (P < 0.05) with a tendency for lower CH 4 production (g/d) relative to the control group. Dry matter intake, ECM and CH 4 production were reduced (P < 0.05) by 0.25%AT inclusion relative to the Control group. Apparent total tract nutrient digestibility (%), ECM per kg DMI, CH 4 yield (g CH 4 /kg DMI) and CH 4 intensity (g CH 4 /kg ECM) were not affected by AT inclusion. Inclusion of AT, at both levels, significantly reduced (P < 0.05) ruminal fluid total short chain fatty acids and molar proportions of actate, while increasing (P < 0.05) the molar proportion of propionate and isovalerate. Inclusion of AT decreased contents (%) of milk fat (P = 0.018) and protein (P = 0.010) resulting in significanly lower fat and protein yields. Lactose content (%) was higher for the AT groups (P = 0.021) but this did not compensate for lower MY resulting in lower milk lactose yield. Milk iodine content increased in a dose dependent manner with AT inclusion. In conclusion, AT inclusion at 0.25% level reduced CH 4 emission from dairy cows with a grass silage-based diets. However, the reduced DMI for the 0.25%AT group along with reduced MY and elevated milk iodine content for both AT groups, for this particular harvest of AT, would suggest possible constraints for large scale inclusion of AT in dairy cow production. [ABSTRACT FROM AUTHOR]

Given the complex and often negative interactions between humanity and nature, methodologies and frameworks for assessing the concepts of circularity (C) and sustainability (S) have become the focus of many studies in the last decade. However, C and S have developed partially independently, impairing the interpretation of their intricate relationships. In this context, there is still no regulatory framework on how to assess them in an integrated manner through simple but robust indicators. To fill this gap, this study proposes an evaluation framework that allows the holistic integration of C and S indicators (integration of CIrcularity and SUstainable indicators – CISU methodology) taking the dairy sector as a case study. For this purpose, 50 Spanish dairy farms have been selected to estimate a Composite Dairy Farm index (CDFi) as a result of the integration of 9 C indicators and 21 S indicators. The results obtained showed a relative homogeneity among dairy farms as well as some room for improvement, with the CDFi (scores from 0 to 100) varying from 36 to 64 points. The results indicate that minimising reliance on external cow feed, use of own-produced fodders, and suitable field management are essential to achieve a circular and sustainable milk production system. This manuscript contributes with the proposal of a novel framework that can be adapted to different companies and products to assess the implementation of CE principles to achieve sustainable development. However, the integration of additional aspects, such as industrial symbiosis, or its applicability at meso level appear as challenges in order to implement sustainable development throughout the supply chain. [Display omitted] • Novel framework to integrate circularity and sustainability indicators is proposed. • The framework is adapted to the dairy sector and applied to 50 farms. • Results of the composite index show relatively low and homogeneous values. • Cow feeding management is a key hot spot to achieve a sustainable and circular farm. • Circular economy principles help to reduce environmental impacts of farms. [ABSTRACT FROM AUTHOR]

• Deep learning models predict milk production better than traditional method. • The deep learning models provide reliable results with short time series. • Increased model complexity does not correspond to an increase in the performance. Forecasting of agricultural variables at national scale is essential for developing policies aimed at guaranteeing food security and increase the stability of the entire agri-food chain. However, this is often a challenging task due to the fact that data are usually sparse and long records are rarely available. This work aims at evaluating the potentiality of ten deep learning models for predicting monthly milk production in France, Germany, and Italy, using as input, climatic and economic variables from open datasets. The results indicate that deep learning models are a better alternative to traditional statistical approaches, providing robust results without requiring complex model architectures. Furthermore, the prominent autoregressive nature of milk production highlights the inability of environmental variables to capture external processes that influence the milk production (e.g., milk quota). However, the high accuracy achieved by the models lays the ground for possible application of deep learning models to accurately forecast agricultural variables at national scale with potential implications for the development of dairy insurance products, and risk management practices. [ABSTRACT FROM AUTHOR]

• Effects of dietary CP and protein digestion kinetics were studied in lactating sows. • Feeding sows a higher percentage of slow protein increased litter weight gain. • A higher dietary CP led to a lower protein utilization efficiency in lactating sows. • Dietary CP can be reduced as long as slow protein sources are used. • A slower protein digestion is preferable from a sustainability point of view. To avoid a high body protein mobilization in modern lean sows during lactation, an adequate dietary amino acid (AA) supply and an efficient AA utilization are crucial. This study evaluated the effects of dietary CP and in vitro protein digestion kinetics on changes in sow body condition, litter weight gain, milk composition, blood metabolites, protein utilization efficiency and subsequent reproductive performance. We hypothesized that a slower digestion of dietary protein would improve AA availability and utilization. In total, 110 multiparous sows were fed one of four lactation diets in a 2 × 2 factorial design, with two CP concentrations: 140 g/kg vs 180 g/kg, and two protein digestion kinetics, expressed as a percentage of slow protein (in vitro degradation between 30 and 240 min): 8 vs 16% of total protein. Feeding sows the high CP diets reduced sow weight loss (Δ = 7.6 kg, P < 0.01), estimated body fat loss (Δ = 2.6 kg, P = 0.02), and estimated body protein loss (Δ = 1.0 kg, P = 0.08), but only at a high percentage of slow protein. A higher percentage of slow protein increased litter weight gain throughout lactation (Δ = 2.6 kg, P = 0.04) regardless of CP concentrations, whereas a higher CP only increased litter weight gain during week 3 of lactation (Δ = 1.2 kg, P = 0.01). On Day 15 postfarrowing, serial blood samples were taken from a subsample of sows fed with the high CP diets. In these sows, a high percentage of slow protein resulted in higher plasma AA concentrations at 150 and 180 min after feeding (Δ = 0.89, P = 0.02, Δ = 0.78, P = 0.03, mmol/L, respectively) and lower increases in urea at 90 and 120 min after feeding (Δ = 0.67, P = 0.04, Δ = 0.70, P = 0.03, mmol/L, respectively). The higher dietary CP concentration increased total nitrogen loss to the environment (Δ = 604 g, P < 0.01) with a reduction of protein efficiency (Δ = 14.8%, P < 0.01). In the next farrowing, a higher percentage of slow protein increased subsequent liveborn litter size (Δ = 0.7, P < 0.05). In conclusion, feeding sows with a high dietary CP concentration alleviated maternal weight loss during lactation when the dietary protein digestion rate was slower, but lowered protein efficiency. A slower protein digestion improved litter weight gain, possibly by reducing AA oxidation and improving plasma AA availability, thus, improving protein efficiency. [ABSTRACT FROM AUTHOR]

Estimation of co-variance components and genetic parameters of fertility and production traits will help to find out the relative importance of genetic and environmental components of each trait and to develop a genetic evaluation system for overall improvement in performances of crossbred cattle of Kerala. In the present study, major fertility trait considered was daughters pregnancy rate (DPR), measures the percentage of non-pregnant animals that become pregnant during each oestrous cycle. Data pertaining to 1180 crossbred cattle sired by 208 Frieswal bulls, spread over a period of 16 years from 2003 to 2019, maintained at different farms of Kerala Veterinary and Animal Sciences University and field centres of ICAR- Filed Progeny Testing Scheme were analysed in the study. Estimates of covariance components and genetic parameters were obtained using restricted maximum likelihood (REML) approach using average information (AI) algorithm. It was observed that DPR had low heritability (0.092 ± 0.03), compared to 305 days milk yield (MY) (0.170 ± 0.094) and fat percent (FP) (0.173 ± 0.072). Phenotypic (r p), genetic (r g) and residual (r e) correlation indicated unfavourable association of fertility with production traits. The estimates of variance and (co)variance components were computed by multivariate animal model. The results indicated that DPR was having lower direct additive (σ2a) 0.046 and environmental variance (σ2c) 0.063 compared to other traits. Highest additive genetic variance (σ2a) 27035.8 was obtained for MY. The study estimates the magnitude of correlations and covariances of fertility and production traits. Since DPR had lower additive genetic variance and negative association with milk production traits in cattle, it would be included as an indirect measure in the evaluation and breeding programs of crossbred cattle of Kerala. • Estimation of co-variance components of major traits are very important for the improvement of overall performances of dairy cattle in a herd. • Daughters pregnancy rate, (DPR) had low heritability (0.092 ± 0.03) compared to 305 days milk yield (0.170 ± 0.094) and fat percent (0.173 ± 0.072). • Daughters pregnancy rate, (DPR) had lower additive genetic (σ2a) 0.046 and environmental variance (σ2c) 0.063, while 305 days milk yield had comparatively higher σ2a (27035) and σ2c (198119). • Fertility traits would be included in the selection criteria of dairy cattle. [ABSTRACT FROM AUTHOR]

Antibiotic dry cow therapy (aDCT) at the end of lactation is an effective mastitis control measure. Selective dry cow therapy means that only infected or presumed-infected cows are treated, instead of aDCT being used as a treatment for all cows. Because antibiotic resistance poses a global threat, livestock production is under increasing pressure to reduce antibiotic use. Changes in management should not, however, impair animal welfare or cause significant economic losses. Our objective was to compare milk yield and somatic cell count (SCC) between aDCT-treated and untreated cows in herds that used selective aDCT, taking into account risk factors for reduced yield and high SCC. The information source was 2015 to 2017 Dairy Herd Improvement data, with 4,720 multiparous cows from 172 Finnish dairy farms. The response variables were test-day milk yield (kg/d) and naturally log-transformed composite SCC (×1,000 cells/mL) during the first 154 d in milk (DIM). The statistical tool was a linear mixed-effects model with 2-level random intercepts, cows nested within herds, and a first-order autoregressive [AR(1)] correlation structure. The overall proportion of aDCT-treated cows was 25% (1,176/4,720). Due to the interaction effect, SCC on the last test day prior to dry-off affected postcalving milk yield differently in aDCT-treated cows than in untreated cows. A higher SCC prior to dry-off correlated with a greater daily yield difference after calving between cows treated and untreated. The majority of cows had SCC < 200,000 cells/mL before dry-off, and as SCC before dry-off decreased, difference in yield between aDCT-treated and untreated cows decreased. Postcalving SCC was lower for aDCT-treated cows compared with untreated cows. To illustrate, for cows with an SCC of 200,000 cells/mL before dry-off, compared with untreated cows, aDCT-treated cows produced 0.97 kg/d more milk and, at 45 DIM, had an SCC that was 20,000 cells/mL lower. Higher late-lactation SCC and lactational mastitis treatments were associated with higher postcalving SCC. A dry period lasting more than 30 d was associated with higher yields but not with SCC. Our findings indicate that a missed aDCT treatment for a high-SCC cow has a negative effect on subsequent lactation milk yield and SCC, which emphasizes the importance of accurate selection of cows to be treated. [ABSTRACT FROM AUTHOR]

Two experiments were conducted to investigate the production effects of N -acetyl- l -methionine (NALM; experiment 1) and to estimate its bioavailability (BA) and rumen escape (RE; experiment 2), respectively, in lactating dairy cows. In experiment 1, 18 multiparous Holstein cows were used in a replicated, 3 × 3 Latin square design experiment with three 28-d periods. Treatments were (1) basal diet estimated to supply 45 g/d digestible Met (dMet) or 1.47% of metabolizable protein (MP; control), (2) basal diet top-dressed with 32 g/d of NALM to achieve dMet supply of 2.2% of MP, and (3) basal diet top-dressed with 56 g/d of NALM to achieve dMet supply of 2.6% of MP. The NALM treatments supplied estimated 17 and 29 g/d dMet from NALM, respectively, based on manufacturer's specifications. In experiment 2, 4 rumen-cannulated lactating Holstein cows were used in a 4 × 4 Latin square design experiment with four 12-d periods. A 12-d period for baseline data collection and 4 d for determination of RE of NALM preceded the Latin square experiment. For determination of RE, 30 g of NALM were dosed into the rumen simultaneously with Cr-EDTA (used as a rumen fluid kinetics marker) and samples of ruminal contents were collected at 0 (before dosing), 1, 2, 4, 6, 8, 10, 14, 18, and 24 h after dosing. Rumen escape of NALM was calculated using the estimated passage rate based on the measured Cr rate of disappearance. Bioavailability of abomasally dosed NALM was determined using the area under the curve of plasma Met concentration technique. Two doses of l -Met (providing 7.5 and 15 g of dMet) and 2 doses of NALM (11.2 and 14.4 g of dMet) were separately pulse-dosed into the abomasum of the cows and blood was collected from the jugular vein for Met concentration analysis at 0 (before dosing), 1, 2, 4, 6, 8, 10, 12, 14, 18, and 24 h after dosing. Supplementation of NALM did not affect DMI, milk yield, feed efficiency, or milk protein and lactose concentrations and yields in experiment 1. Milk fat concentration and energy-corrected milk yield decreased linearly with NALM dose. Plasma Met concentration was not affected by NALM dose. The estimated relative BA of abomasally dosed NALM (experiment 2) was 50% when dosed at 14.4 g/cow (11.2 g/d dMet from NALM) and 24% when dosed at 28.8 g/cow (14.4 g/d dMet from NALM). The estimated RE of NALM was 19% based on the measured k p of Cr at 11%/h. The total availability of ingested NALM was estimated at 9.5% for the lower NALM dose when taking into account RE (19%) and bioavailability in the small intestine (50%). Overall, NALM supplementation to mid-lactation dairy cows fed a MP-adequate basal diet below NRC (2001) recommendations (45 g/d or 1.47% Met of MP) decreased milk fat and energy-corrected milk yields but did not affect milk or milk true protein yields. Further evaluation of BA of NALM at different doses is warranted. In addition, intestinal conversion of NALM to Met needs additional investigation to establish a possible saturation of the enzyme aminoacylase I at higher NALM doses. [ABSTRACT FROM AUTHOR]

The objective of this experiment was to investigate the effect of dietary levels of digestible histidine (dHis) and MP on lactational performance and plasma and muscle concentrations of free AA in dairy cows. A randomized block design experiment was conducted with 48 Holstein cows, including 20 primiparous, averaging (±SD) 103 ± 22 d in milk and 45 ± 9 kg/d milk yield at the beginning of the experiment. A 2-wk covariate period preceded 12 experimental wk, of which 10 wk were for data and sample collection. Experimental treatments were (1) MP-adequate (MPA) diet with 2.1% dHis of MP (MPA2.1), (2) MPA with 3.0% dHis (MPA3.0), (3) MP-deficient (MPD) diet with 2.1% dHis (MPD2.1), and (4) MPD with 3.0% dHis (MPD3.0). Actual dHis supply was estimated at 64, 97, 57, and 88 g/d, respectively. Diets supplied MP at 110% (MPA) and 96% (MPD) of NRC 2001 dairy model requirements calculated based on DMI and production data during the experiment. Dry matter intake and milk yield data were collected daily, milk samples for composition and blood samples for AA analysis were collected every other week, and muscle biopsies at the end of covariate period, and during wk 12 of the experiment. The overall DMI was not affected by dHis or MP level. Milk yield tended to be increased by 3.0% dHis compared with 2.1% dHis. Milk true protein concentration and yield were not affected by treatments, whereas milk urea nitrogen concentration was lower for MPD versus the MPA diet. Milk fat concentration was lower for MPD versus MPA. There was a MP × dHis interaction for milk fat yield and energy-corrected milk; milk fat was lower for MPD3.0 versus MPD2.1, but similar for cows fed the MPA diet regardless of dHis level whereas energy-corrected milk was greater for MPA3.0 versus MPA2.1 but tended to be lower for MPD3.0 versus MPD2.1. Plasma His concentration was greater for cows fed dHis3.0, and concentration of sum of essential AA was greater, whereas carnosine, 1-Methyl-His and 3-Methyl-His concentrations were lower for cows fed MPA versus MPD diet. Muscle concentration of His was greater for cows fed dHis3.0 treatment. The apparent efficiency of His utilization was increased at lower MP and His levels. Overall, cows fed a corn silage-based diet supplying MP at 110% of NRC (2001) requirements tended to have increased ECM yield and similar milk protein yield to cows fed a diet supplying MP at 96% of requirements. Supplying dHis at 3.0% of MP (or 86 and 96 g/d, for MPD3.0 and MPA3.0, respectively) tended to increase milk yield and increased plasma and muscle concentrations of His but had minor or no effects on other production variables in dairy cows. [ABSTRACT FROM AUTHOR]