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Heat stress during late gestation in cattle negatively affects the performance of the dam and its calf. This brief exposure to an adverse environment before parturition affects the physiological responses, tissue development, metabolism, and immune function of the dam and her offspring, thereby limiting their productivity. During the dry period of a dairy cow, heat stress blunts mammary involution by attenuating mammary apoptosis and autophagic activity and reduces subsequent mammary cell proliferation, leading to impaired milk production in the next lactation. Dairy cows in early lactation that experience prepartum heat stress display reduced adipose tissue mobilization and lower degree of insulin resistance in peripheral tissues. Similar to mammary gland development, placental function is impaired by heat stress as evidenced by reduced secretion of placental hormones (e.g. estrone sulfate) in late gestation cows, which partly explains the reduced fetal growth rate and lighter birth weight of the calves. Compared with dairy calves born to dams that are exposed to evaporative cooling during summer, calves born to noncooled dry cows maintain lower BW until 1 yr of age, but display a stronger ability to absorb glucose during metabolic challenges postnatally. Immunity of the calves, both passive and cell-mediated immune function, is also impaired by prenatal heat stress, resulting in increased susceptibility of the calves to diseases in their postnatal life. In fact, dairy heifers born to heat-stressed dry cows without evaporative cooling have a greater chance leaving the herd before puberty compared with heifers born to dry cows provided with evaporative cooling (12.2% vs. 22.7%). Dairy heifers born to late-gestation heat-stressed dry cows have lower milk yield at maturity during their first and second lactations. Emerging evidence suggests that late-gestation heat stress alters the mammary gland microstructure of the heifers during the first lactation and exerts epigenetic alterations that might explain, in part, their impaired productivity. [ABSTRACT FROM AUTHOR]

Despite its low NDF digestibility, sugarcane is an option for feeding dairy cattle in tropical regions. We evaluated the effect of sugarcane silages inoculated with Lactobacillus hilgardii CCMA 0170 (LH; an epiphytic bacteria isolated from sugarcane) or with L. buchneri NCIMB 40788 (LB; a commercial strain isolated from temperate grasses) on dairy cow performance and feeding behavior. The microbial inoculums were previously grown in the laboratory to obtain 5 log cfu/g of fresh forage. Nine tons of each inoculated silage and a noninoculated control silage (CON) were harvested from the same field and stored for at least 35 d in experimental 20 × 2.1 × 0.4 m bunker silos. Fifteen Holstein cows in late lactation (336 ± 175 days in milk at the start of the experiment) received the treatments in five 3 × 3 Latin squares with 21-d periods. The diets contained 20% of DM of sugarcane silage and 41% of DM of corn silage. Milk yield was increased from 18.0 kg/d for CON to18.8 kg/d for LH, but LB did not elicit a detectable increase in milk yield (18.1 kg/d). The daily yields of fat, protein, lactose, and total solids were increased by LH. Daily DMI and total tract apparent digestibility of nutrients did not differ among treatments. Both inoculated silages reduced acetate and increased butyrate proportions in ruminal VFA, but only LH silage reduced the acetate to propionate ratio (3.0 vs. 3.3). First meal duration was shorter for CON compared to LH and LB. The proportion of daily intake between 0700 and 1300 h tended to be increased, and the proportion between 1900 and 0700 h was reduced by LH. The inoculation of sugarcane silage with Lactobacillus hilgardii affected rumen fermentation profile and feeding behavior of late lactation dairy cows, increasing the yield of milk solids. [ABSTRACT FROM AUTHOR]

The study objective was to evaluate the effects of reducing dietary starch content in fresh cow diets while maintaining NDF levels by substituting barley grain (BG), corn silage (CS), or both with beet pulp (BP) on nutrient digestion, ruminal fermentation, DMI, lactation performance, meal patterns, chewing activity, and sorting behavior. Thirty-six multiparous cows were randomly assigned to 1 of 4 experimental diets from calving to 21 d in lactation. Experimental diets were a high-starch diet with ground BG (CO; 24.9% starch; 0% BP) and 3 lowstarch diets: the CO with BP substituted for ground BG (BB; 19.6% starch; 7% BP), the CO with BP substituted for CS (BC; 20.6% starch; 12% BP), or the CO with BP substituted for CS and ground BG (BCB; 20.3% starch; 12% BP). The CO, BB, BC, and BCB contained 33.4, 34.4, 32.9, and 33.7% NDF, respectively, and 23.1, 22.0, 18.2, and 19.2% forage NDF, respectively. There was no effect of diet on total tract nutrient digestibility (P > 0.20), ruminal pH (P = 0.49), or total VFA (P = 0.39). However, diets affected molar proportions of propionate and acetate (P ≤ 0.01). Relative to CO cows, the molar propionate percentage was less in BB cows (P < 0.01) and tended to be greater in BC cows (P = 0.10), whereas the molar percentage of acetate was less in BC cows than in BB (P < 0.01) and CO cows (P = 0.02). Relative to CO cows (16.50 kg/d), DMI was greater for BC (17.70 kg/d; P < 0.01) and BCB cows (17.50 kg/d; P = 0.01), but it was less in BB cows (15.60 kg/d; P = 0.02). Similar to DMI results, milk yields tended to be greater for BC (37.89 kg/d; P = 0.08) and BCB cows (37.81 kg/d; P = 0.09) compared with CO cows (35.41 kg/d), but BB cows (33.05 kg/d) tended to produce less milk than CO cows (P = 0.1). Milk fat content tended to be less in BC (P = 0.08) and BCB cows (P = 0.10) than in CO cows. There was no effect of diet on eating and rumination patterns (P ≥ 0.18), except shortened meal intervals for BC and BCB cows compared with CO cows (P = 0.02). Dietary treatments did not affect chewing activities per day or bout (P = 0.50), but BC and BCB cows spent less time on chewing activities per kilogram DM (P < 0.01) and NDF intake (P < 0.01) compared with CO cows. Cows fed the BC and BCB sorted for long particles (>19 mm; P < 0.01) but against particles < 1.18 mm (P < 0.01). In the present study, propionate did not seem to play a central role in feed intake regulation of fresh cows, because BB cows had depressed DMI and the lowest molar proportion of propionate. However, reducing starch levels in fresh cow diets by replacing CS and both CS and BG with BP positively affected DMI and milk yield. [ABSTRACT FROM AUTHOR]

Our objective was to compare the ranking of dairy cows according to their methane (CH4) emissions as measured by a respiration chamber (RC) technique and the GreenFeed (GF) technique during 3 periods in second lactation. Two-day CH4 measurements in a RC performed in wk 3, 14, and 42 of lactation were flanked by GF measurements for 20 (period 1 [P1]), 35 (period 2 [P2]), and 35 (period 3 [P3]) days, respectively, before and after RC measurement. This gave the total duration of CH4 measurements using the GF system of 40, 70, and 70 d for P1, P2, and P3, respectively. Mean daily CH4 production (g/d) of the 8 dairy cows was 346, 439, and 430 using the RC technique and 338, 378, and 416 using the GF system during P1, P2, and P3, respectively. Average daily CH4 production determined by the GF technique was 2.4, 13.8, and 3.2% lower in P1, P2, and P3, respectively. Methane normalized to DMI continuously increased from P1 to P3 when measured in a RC, whereas it was lowest during P2 when measured by the GF method. Ranking of the cows according to CH4 production, CH4/energy-corrected milk yield (ECM; CH4/ECM), and CH4/DMI differed between periods no matter which method was used. Cluster analysis including all 3 periods, however, identified the same cows with the highest and lowest CH4 production determined either by the RC technique or the GF system. In conclusion, multiple CH4 measurements at different stages of lactation are necessary for reliable discrimination of highest and lowest CH4 emitting cows and the GF system may be used to discriminate the extremes. [ABSTRACT FROM AUTHOR]

Body fatness and degree of body fat mobilization in cows vary enormously during their reproduction cycle and influence energy partitioning and metabolic adaptation. The objective of the study was to test bioelectrical impedance spectroscopy (BIS) as a method for predicting fat depot mass (FDM), in living cows. The FDM is defined as the sum of subcutaneous, omental, mesenteric, retroperitoneal, and carcass fat mass. Bioelectrical impedance spectroscopy is compared with the prediction of FDM from the deuterium oxide (D2O) dilution method and from body conformation measurements. Charolais × Holstein Friesian (HF; n = 18; 30 d in milk) crossbred cows and 2 HF (lactating and nonlactating) cows were assessed by body conformation measurements, BIS, and the D2O dilution method. The BCS of cows was a mean of 3.68 (SE 0.64). For the D2O dilution method, a bolus of 0.23 g/kg BW D2O (60 atom%) was intravenously injected and deuterium (D) enrichment was analyzed in plasma and whey by stabile isotope mass spectrometry, and total body water content was calculated. Impedance measurement was performed using a 4-electrode interface and time domain-based measurement system consisting of a voltage/current converter for applying current stimulus and an amplifier for monitoring voltage across the sensor electrodes. For the BIS, we used complex impedances over three frequency decades that delivers information on intra- and extracellular water and capacity of cell membranes. Impedance data (resistance of extra- and intracellular space, cell membrane capacity, and phase angle) were extracted 1) by simple curve fit to extract the resistance at direct current and high frequency and 2) by using an electrical equivalent circuit. Cows were slaughtered 7 d after BIS and D enrichment measurements and dissected for the measurement of FDM. Multiple linear regression analyses were performed to predict FDM based on data obtained from body conformation measurements, BIS, and D enrichment, and applied methods were evaluated by cross-validation. The FDM varied widely between cows and was correlated to D enrichment in plasma (r = 0.91, P < 0.05). Prediction of FDM by body size measurements was less precise (R² = 0.84), but FDM prediction was more accurate using D enrichment in plasma (R² = 0.90) and BIS (R² = 0.99) data. Therefore, both BIS and D enrichment analysis resulted in similarly good predictions of FDM in cows, and we conclude that BIS could have the potential to predict FDM in dairy cows from 40 to 380 kg. [ABSTRACT FROM AUTHOR]

Eight 4-ha mixed warm-season grass pastures in southwestern Arkansas (33°40′4″ N, 93°35′24″ W, and elevation 107 m) were stocked with either large mature size (571 kg [SD 55.2] BW) or small mature size (463 kg [SD 58.2] BW) springcalving cows at 4 stocking rates (SR; 1, 1.5, 2, or 2.5 cow–calf pairs/ha) over 4 yr to test the effects of SR and mature body size on cow and calf performance and system economics. Each pasture received 112 kg/ha N as ammonium nitrate in May and was broadcast seeded to annual ryegrass (Lolium multiflorum Lam.) in mid October each fall along with 112 kg/ha N as ammonium nitrate. Data were analyzed by regression to determine the effects of cow size and SR on calf performance, cow BW change, calf gain, weaning weight per hectare, hay feeding requirements, and net returns. As SR increased, cow BW and BCS at weaning decreased (P < 0.01) by 26 kg and 0.36 condition scores, respectively, for each additional cow stocked per hectare (R2 = 0.44). Calf BW at weaning in October increased (P < 0.01) 19 kg for each 100-kg increase in cow BW but was not affected (P = 0.66) by SR. As cow BW increased, calf BW at weaning per 100 kg cow BW decreased (P < 0.01) 6.7 kg for each 100-kg increase in cow BW but was not affected (P = 0.44) by SR. Neither cow BW nor SR affected (P ≥ 0.53) pregnancy percentage, which averaged 88% over the 4-yr experiment. Calf BW weaned per hectare was not affected (P = 0.75) by cow BW but linearly increased (P < 0.01) by 217 kg for each additional cow per hectare SR. Hay feeding days and cost of hay per cow increased (P ≤ 0.05) and kilograms of hay offered per cow tended (P = 0.09) to linearly increase with increasing SR, yet cow BW had no effects (P > 0.22). Although there were no effects (P ≥ 0.38) of cow BW on carrying cost or net returns, increasing SR decreased (P < 0.01) total expenses by US$102/cow and increased net returns by $70/cow and $438/ha for each cow per hectare increase in SR. These data indicate that increasing cow size can increase weaning BW of calves but does not affect total production per hectare or profitability, even though weaning weight efficiency ratios were reduced. Increasing SR reduced cow BW and BCS at weaning and increased feeding of conserved forages but did not affect pregnancy rates and led to increases in total calf BW weaned per hectare and net returns. [ABSTRACT FROM AUTHOR]

Cow size has been suggested to be an important consideration for selecting cattle to match their production environment. Over the last several decades, the trend in genetic selection for maximum growth has led to gradual increases in beef cow size. An unrelated trend during this same period in the western United States has been an increase in temperature, drought frequency, and drought severity. Due to the potential influence of the increasing cow size trend on nutritional maintenance costs and production, we assessed the effect of cow size on weaning weight and efficiency in relation to drought on a semiarid high-elevation ranch in Wyoming. This study addresses a lack of empirical studies on the interaction between cow size and drought. We measured calf weaning weights of 80 Angus ? Gelbvieh cows from 2011 to 2014 and assessed how drought affected weaning weights, efficiency (considered as calf weight relative to cow weight), intake requirements, and potential herd sizes relative to cow size. We stratified cows into 5 weight classes (453, 498, 544, 589, and 634 kg) as a proxy for cow size and adjusted weaning weights to a 210-d calf sex adjusted value. Cow size was a significant factor every year, with different cow sizes having advantages or disadvantages different years relative to weaning weight. However, efficiency for the smallest cows (453 kg) was always greater than efficiency for largest cows (634 kg; P < 0.001). Efficiency for the smallest cows was greater in the driest year (0.41 ± 0.02) than efficiency of the largest cows in the wettest years (0.37 ± 0.01). The change in efficiency (?E) between wet and dry years was 0.18 for the smallest cow size and 0.02 for the largest cow size, and ?E decreased as cow size increased. This is an indication of the ability of smaller cows to lower maintenance requirements in response to changes in the production environment but with optimal upside potential when conditions are favorable. These results indicate large cows (589 to 634 kg) do not maximize genetic potential in this production environment when conditions are optimum or provide any advantage over small or moderate size cows (453 to 544 kg) across the drought gradient. [ABSTRACT FROM AUTHOR]

Spring-calving, mature cows (n = 191 total) and their progeny were used to evaluate the effects of late gestation drylot rations differing in RUP and fat content on cow performance as well as performance and carcass characteristics of subsequent progeny. Cows were blocked by BW and anticipated calving date and assigned to 16 pens. Pens were randomly allotted to 1 of 2 treatments: limit-fed corn coproducts and ground cornstalks (COP; TDN = 64.4%, CP = 11.1%, RDP = 60.2% of CP, and fat = 5.1%) or limit-fed ground mixed, cool-season grass hay (HY; TDN = 55.7%, CP = 9.5%, RDP = 86.0% of CP, and fat = 2.3%). Treatments were limit fed as isocaloric, isonitrogenous rations from 88 ± 11 d prepartum to calving. All cows were fed a common diet postpartum. Cow BW and BCS were collected at the beginning of the feeding period, within 48 h after calving, and at breeding. Calf BW was collected at birth and at 64 ± 11 and 124 ± 11 d of age. Milk production was determined using the weigh-suckle-weigh technique at 64 ± 11 and 124 ± 11 d postpartum. At 124 ± 11 d of age, steers (n = 68) and nonreplacement heifer calves (n = 25) were weaned and placed on a common feedlot diet with individual feed intake monitored using GrowSafe. Feedlot calves were slaughtered at a commercial facility 35 ± 10 d after a minimum ultrasound 12th-rib fat thickness estimation of 0.9 cm. After calving, cow BW was greater (P < 0.01) and BCS was greater (P < 0.01) for cows fed COP than for cows fed HY. Calf birth BW was greater (P = 0.04) for those born to cows fed COP with no difference (P = 0.43) in percentage of unassisted births across treatment. Cows fed HY were lighter (P < 0.01) at breeding with lower BCS (P = 0.03); nevertheless, overall pregnancy rate was not different (P = 0.80). No differences (P = 0.22) in milk production were detected. For feedlot progeny, initial feedlot BW, final BW, and days on feed were not different (P ≥ 0.23), and as a result, no difference (P = 0.21) in feedlot ADG was detected. Feedlot DMI and G:F were not different (P ≥ 0.19) across treatments. Feedlot calf health was monitored with no differences (P ≥ 0.68) in morbidity and mortality observed. No differences (P ≥ 0.27) were detected for HCW, LM area, backfat, marbling score, yield grade, or KPH. Increased dietary RUP and fat content during late gestation increased cow BW and BCS but did not alter milk production, subsequent reproduction, or subsequent calf performance or carcass characteristics. [ABSTRACT FROM AUTHOR]

Nutrigenomics in dairy cows is a relatively new area of research. It is defined as the study of the genomewide influences of nutrition altering the expression of genes. Dietary compounds affect gene expression directly or indirectly via interactions with transcription factors. Among those, the most relevant for nutrigenomics are ligand-dependent nuclear receptors, especially peroxisome proliferator-activated receptors (PPAR) and liver X receptor. Among other transcription factors, a prominent nutrigenomic role is played by the sterol regulatory element-binding protein 1 (SREBP1). Data from studies on dairy cows using gene expression and gene reporters among the main molecular methods used to study nutrigenomics in dairy cows are indicative of a network of multiple transcription factors at play in controlling the nutrigenomic responses. Fatty acids, AA, and level of feed and energy intake have the strongest nutrigenomic potential. The effect of t10,c12 CLA on depressing milk fat synthesis via inhibition of SREBP1 was among the first and likely the best-known nutrigenomic example in dairy cows. Although long-chain fatty acids (LCFA) are clearly the most potent, a nutrigenomic role for short-chain fatty acids is emerging. Available data indicate that saturated compared with unsaturated LCFA have a more potent nutrigenomic effect in vitro, likely through PPAR. In vivo, the effect of saturated LCFA is more modest, with contrasting effects among tissues. Nutrigenomic effects of AA are emerging, particularly for the regulation of milk protein synthesis-associated genes. The level of energy in the diet has a strong and broad nutrigenomic effect and appears to "prime" tissue metabolism, particularly liver. We are at the frontier of the nutrigenomics era in ruminants and initial data strongly indicate that this scientific branch (and spinoffs such as nutriepigenomics) can play a critical role in future strategies to better feed dairy cattle. [ABSTRACT FROM AUTHOR]

In early lactation, susceptibility to disease is greatest, impacting cow health and productivity and leading to economic losses. Mastitis is the most economically costly disease to the dairy industry and is most frequent at this time. The objective of this paper is to discuss the energetic fuels used by leukocytes in the metabolic response during mastitis that may reveal potential mechanisms linking mastitis with the development of subsequent metabolic diseases for dairy cows during lactation. Glucose and glutamine are the primary fuels used by leukocytes and are essential substrates for optimal leukocyte function. Yet because these substrates are in high demand to support milk synthesis during early lactation, their supply to leukocytes may be compromised and may partly contribute to immunosuppression observed at this time. Production-related metabolic diseases during early lactation, such as ketosis and hepatic lipidosis, can also adversely affect health and productivity. Risk of subsequent disease for cows during mastitis has not been fully elucidated. Regardless of stage of lactation and physiological state, increases in circulating NEFA and glucose and decreases in ketones during an intramammary inflammation in dairy cows have been reported. In addition, previous work indicates that hepatic metabolism may be impaired during inflammation. These results indicate a potential link between mastitis and the risk of subsequent metabolic disease for dairy cows during lactation. This paper will discuss the complex relationships between metabolism and immune function and how these immunometabolic interactions relate mastitis with increased risk of subsequent disease during early lactation. [ABSTRACT FROM AUTHOR]

A major role of the dairy cow is to convert low-quality plant materials into high-quality protein and other nutrients for humans. We must select and manage cows with the goal of having animals of the greatest efficiency matched to their environment. We have increased efficiency tremendously over the years, yet the variation in productive and reproductive efficiency among animals is still large. In part, this is because of a lack of full integration of genetic, nutritional, and reproductive biology into management decisions. However, integration across these disciplines is increasing as the biological research findings show specific control points at which genetics, nutrition, and reproduction interact. An ordered systems biology approach that focuses on why and how cells regulate energy and N use and on how and why organs interact through endocrine and neurocrine mechanisms will speed improvements in efficiency. More sophisticated dairy managers will demand better information to improve the efficiency of their animals. Using genetic improvement and animal management to improve milk productive and reproductive efficiency requires a deeper understanding of metabolic processes throughout the life cycle. Using existing metabolic models, we can design experiments specifically to integrate data from global transcriptional profiling into models that describe nutrient use in farm animals. A systems modeling approach can help focus our research to make faster and larger advances in efficiency and determine how this knowledge can be applied on the farms. [ABSTRACT FROM AUTHOR]

Tea saponin is considered a promising natural compound for reducing enteric methane emissions in ruminants. A trial was conducted to study the effect of this plant extract fed alone or in combination with nitrate on methane emissions, total tract digestive processes, and ruminal characteristics in cattle. The experiment was conducted as a 2 2 factorial design with 4 ruminally cannulated nonlactating dairy cows. Feed offer was restricted to 90% of voluntary intake and diets consisted of (DM basis): 1) control (CON; 50% hay and 50% pelleted concentrates), 2) CON with 0.5% tea saponin (TEA), 3) CON with 2.3% nitrate (NIT), and 4) CON with 0.5% tea saponin and 2.3% nitrate (TEA+NIT). Tea saponin and nitrate were included in pelleted concentrates. Diets contained similar amounts of CP (12.2%), starch (26.0%), and NDF (40.1%). Experimental periods lasted 5 wk including 2 wk of measurement (wk 4 and 5), during which intake was measured daily. In wk 4, daily methane emissions were quantified for 4 d using open circuit respiratory chambers. In wk 5, total tract digestibility, N balance, and urinary excretion of purine derivatives were determined from total feces and urine collected separately for 6 d. Ruminal fermentation products and protozoa concentration were analyzed from samples taken after morning feeding for 2 nonconsecutive days in wk 5. Tea saponin and nitrate supplementation decreased feed intake (P < 0.05), with an additive effect when fed in combination. Compared with CON, tea saponin did not modify methane emissions (g/kg DMI; P > 0.05), whereas nitrate-containing diets (NIT and TEA+NIT) decreased methanogenesis by 28%, on average (P < 0.001). Total tract digestibility, N balance, and urinary excretion of purine derivatives were similar among diets. Ruminal fermentation products were not affected by tea saponin, whereas nitrate-containing diets increased acetate proportion and decreased butyrate proportion and ammonia concentration (P < 0.05). Under the experimental conditions tested, we confirmed the antimethanogenic effect of nitrate, whereas tea saponin alone included in pelleted concentrates failed to decrease enteric methane emissions in nonlactating dairy cows [ABSTRACT FROM AUTHOR]

The effects of different feeding strategies (0.7 kg/d target ADG [LO] and 1.0 kg/d target ADG [HI] during the lactation period (LACT; 0-6 mo) and the rearing period (REAR; 6-15 mo; HI-HI, HI- LO, LO-HI, and LO-LO treatments) on the growth and reproductive parameters of beef heifers bred by fixed-time AI at 15 mo were analyzed. Animal weights were recorded weekly (from birth to 18 mo), and size measures were recorded at 6 and 15 mo. Heifers were bled to determine the onset of puberty and the metabolic and endocrine (IGF-I and leptin) status. During lactation, calves in the high lactation treatment (LactHI) had greater weight (P < 0.001), weight gain (P < 0.001), and body size (P < 0.001) than calves in the low lactation treatment (LactLO). The greater energy balance of LactHI heifers at weaning was reflected in greater concentrations of plasma glucose (P < 0.001), urea (P < 0.001), and IGF-I (P < 0.001); plasma levels of NEFA were lower (P < 0.001). During REAR, LactLO heifers had a greater growth rate than did LactHI heifers (P < 0.001), partially overcoming the lower gains during lactation. The differences in size measurements registered at weaning were also compensated, with the exception of LO-LO heifers. The IGF-I profile was highly correlated with animal performance traits and metabolic profiles, providing a useful indicator of growth, nutritional, and metabolic status at key points in development. By contrast, the function of leptin as an indicator of growth and reproductive development of heifers was less clear. All treatments had similar weights at puberty onset (55.9% mature BW), although LactLO (P < 0.01) and the low rearing treatment (RearLO; P < 0.001) heifers were older than the others. The animals with greater glucose and IGF-I levels at weaning and greater cholesterol concentrations during REAR reached puberty earlier. The fertility rate (86%) was similar among treatments. The heifers in the high rearing treatment (RearHI) required more AI services to become pregnant and were older at conception (P < 0.05). The age of conception was positively correlated with glucose (r = 0.57, P < 0.01) and cholesterol (r = 0.68, P < 0.001) at 9 mo. Our results show that a 0.7 kg/d gain from birth allowed the first breeding at 15 mo, 6 mo earlier than usual for these conditions, without any negative effect on heifer reproductive performance. [ABSTRACT FROM AUTHOR]

The main objective of this experiment was to study the γ-glutamyl transferase (GGT) activity in milk during lactation and its relationship with metabolic status of dairy cows, milk yield, milk composition, and cheesemaking properties. The study was performed in a tied stall barn and involved 20 lactations from 12 healthy multiparous Italian Friesian dairy cows. During lactation starting at d 10, milk samples were collected weekly and analyzed for composition, somatic cells count, titratable acidity, and milk coagulation properties. The GGT activity was measured in defatted samples. Blood samples were collected weekly to assess biochemical indicators related to energy, protein, and mineral metabolism, markers of inflammation and some enzyme activities. The lactations of each cow were retrospectively categorized into 2 groups according to their milk GGT activity value through lactation. A median value of GGT activity in the milk of all lactations was calculated (3,045 U/L), and 10 lactations with lower GGT activity were classified as low while 10 lactations with greater GGT activity were classified as high. The average value of milk GGT activity during lactation was 3,863 and 3,024 U/L for high and low, respectively. The GGT activity decreased in early lactation and reached minimum values in the second month (3,289 and 2,355 U/L for high and low, respectively). Thereafter GGT activity increased progressively, reaching values in late lactation of 4,511 and 3,540 U/L in high and low, respectively. On average, milk yield was 40.81 and 42.76 kg/d in high and low, respectively, and a negative partial correlation with milk GGT activity was observed. A greater milk protein concentration was observed in high (3.39%) compared with low (3.18%), and a positive partial correlation with milk GGT activity was observed. Greater titratable acidity in high than that in low (3.75 vs. 3.45 degrees Soxhlet-Henkel/50 mL, respectively) was also observed. Plasma glucose was greater in cows of high than in low group, while plasma urea was lower in the high than in the low group. No relationship between plasma GGT and milk GGT activity was observed. Our results show an important effect of lactation stage on milk GGT activity. The individual effect observed from consecutive lactations and the relationship between milk GGT activity and milk protein concentration in healthy cows could open prospects for GGT as a future tool in improving milk protein content. [ABSTRACT FROM AUTHOR]

Genetic correlations of selection indi-ces and the traits considered in these indices with mature weight (MW) of Nelore females and corre-lated responses were estimated to determine whether current selection practices will result in an undesired correlated response in MW. Genetic trends for wean-ing and yearling indices and MW were also estimated. Data from 612,244 Nelore animals bom between 1984 and 2010, belonging to different beef cattle evaluation programs from Brazil and Paraguay, were used. The following traits were studied: weaning conformation (WC), weaning precocity (WP), weaning muscling (WM), yearling conformation (YC), yearling precoc-ity (YP), yearling muscling (YM), weaning and year-ling indices, BW gain from birth to weaning (BWG), postweaning BW gain (PWG), scrotal circumference (SC), and MW. The variance and covariance compo-nents were estimated by Bayesian inference in a multi-trait analysis, including all traits in the same analysis, using a nonlinear (threshold) animal model for visual scores and a linear animal model for the other traits. The mean direct heritabilities were 0.21 ± 0.007 (WC), 0.22 ± 0.007 (WP), 0.20 ± 0.007 (WM), 0.43 ± 0.005 (YC), 0.40 ± 0.005 (YP), 0.40 ± 0.005 (YM), 0.17 ± 0.003 (BWG), 0.21 ± 0.004 (PWG), 0.32 ± 0.001 (SC), and 0.44 ±0.018 (MW). The genetic correla-tions between MW and weaning and yearling indices were positive and of medium magnitude (0.30 ± 0.01 and 0.31 ± 0.01, respectively). The genetic changes in weaning index, yearling index, and MW, expressed as units of genetic SD per year, were 0.26, 0.27, and 0.01, respectively. The genetic trend for MW was nonsignifi-cant, suggesting no negative correlated response. The selection practice based on the use of sires with high final index giving preference for those better ranked for yearling precocity and muscling than for conformation generates only a minimal correlated response in MW. [ABSTRACT FROM AUTHOR]

The objective of this experiment, part of a larger study, was to investigate changes in rumen bacterial, archaeal, and fungal diversity in cows fed medium-chain saturated fatty acids. In the main study, 6 lactating dairy cows were dosed intraruminally with 240 g/(cow.d) of stearic (SA, control), lauric (LA), or myristic (MA) acid in a replicated 3 × 3 Latin square design trial. Experimental periods were 28 d, and cows were transfaunated between periods. Lauric acid decreased protozoal counts in the rumen by 96% compared with SA and MA (compared with SA, MA had no effect on ruminal protozoa). Whole ruminai contents samples were collected 2, 4, 6, 8, 10, 14, 18, and 24 h after the morning feeding on d 23 of each experimental period, stored frozen, and later composited by cow and period for microbial profile analyses, which involved tag-encoded flexible (FLX) amplicon pyrosequencing to provide diversity analyses of gastrointestinal bacterial, archaeal, and fungal populations of the cattle. The LA treatment, either directly or through its effect on protozoa, had a profound effect on the microbial ecology of the rumen. Ruminai populations of Prevotella, Bacteroides, and Enterorhabdus were decreased (P = 0.04 to P < 0.001) by more than 2-fold in LA treatments compared with SA, and Clostridium populations were decreased (P = 0.01) in LA- compared with MA-treated cows. The proportion of Ruminococcus was not affected by treatment, although the LA treatment had the least proportion of Ruminococcus. Proportions of Eubacterium, Butyrivibrio, Olsenella, and Lactobacillus genera were increased (P = 0.03 to 0.01) by LA compared with MA or SA. The LA treatment, possibly through its effect on protozoa physically associated with archaea, resulted in an increase (P = 0.01) in the archaeal methanogenic genus Methanosphaera and a decrease (P = 0.01) in Methanobrevibacter. Few changes in fungal populations caused by treatment were detected. Collectively, results indicate that LA, either through antiprotozoal or direct antimicrobial effects, altered bacterial and archaeal populations in the rumen of dairy cows, but effects on fungal populations were not clear. [ABSTRACT FROM AUTHOR]

The objectives were to evaluate effects of maternal nutrient restriction and stage of gestation on maternal and fetal visceral organ mass and indices of jejunal growth and vascularity in beef cows. Thirty multiparous beef cows (BW = 571 ± 63 kg; BCS = 5.4 ± 0.7) carrying female fetuses (d 30 of gestation) were allocated to receive a diet of native grass hay (CON; 12.1% CP, 70.7% IVDMD, DM basis) to meet NRC recommendations for BW gain during early gestation or a nutrient-restricted diet of millet straw (NR; 9.9% CP, 54.5% IVDMD, DM basis) to provide 68.1% of NEm, and 86.7% of MP estimated requirements. On d 125 of gestation, 10 CON and 10 NR cows were killed and necropsied. Five remaining CON cows received the CON diet, and 5 NR cows were realimented with a concentrate supplement (13.2% CP, 77.6% IVDMD, DM basis) and the CON hay to achieve a BCS similar to CON cows by d 220 of gestation. Remaining cows were necropsied on d 245 of gestation. Cow BW and eviscerated BW (EBW) were less (P < 0.01) for NR than CON at d 125 but did not differ (P > 0.63) at d 245. Cows fed the CON diet had greater (P < 0.09) total gastrointestinal (GI) tract, omasal, and pancreatic weights. Stomach complex, ruminal, and liver weights were greater for CON than NR cows (P < 0.09) 011 d 125. Total GI, stomach complex, and pancreatic weights increased (P < 0.001) with day of gestation. Restricted cows had decreased (P = 0.09) duodenal RNA:DNA compared with CON. Duodenal DNA was less (P = 0.01) and jejunal RNA:DNA (P = 0.09) was greater for cows at d 125 vs. 245. Cow jejunal capillary area density increased with day of gestation (P = 0.02). Fetal BW and EBW were unaffected by dietary treatment (P ⩾ 0.32). Total GI tract and all components increased in mass with day of gestation (P < 0.001). Fetuses from NR dams had greater (P = 0.003) reticular mass at d 245 than CON fetuses. Fetuses from NR cows had greater (P = 0.02) percent jejunal proliferation at d 125 and greater (P = 0.03) total intestinal vascularity (mL) at d 245. Fetal jejunal DNA decreased (P = 0.09), RNA:DNA increased (P = 0.05), and total jejunal proliferating cells increased (P < 0.001) with day of gestation. Jejunal capillary area density, number density, and surface density were greater (P < 0.008) during late gestation. Results indicate that maternal and fetal intestines undergo changes during gestation, which can be affected by nutrient restriction and may partially explain differences observed in fetal development and postnatal performance. [ABSTRACT FROM AUTHOR]

Two experiments evaluated short–term controlled internal drug release (CIDR) insert–based protocols to synchronize estrus and ovulation and cornlare differences in their potential to facilitate fixedtime AT (FTAI) in postpartum beef cows. Experiment 1 was designed to compare the 7and 5–d Select Synch + CIDR protocols on the basis of timing and synchrony of estrus after treatment. Cows assigned to the 7–d protocol (n = 59) received GnRH [100 μg intramuscularly (i.m.)] and CIDR inserts (1.38 g of progesterone) on d O and PGF21, (25 mg i.m.) and CIDR removal on d 7. Cows assigned to the 5–d protocol (n = 58) received GnRH and CIDR. inserts on d 2, PGF2α(, and CIDR removal on d 7, and a second injection of PGF2α 12 h after CIDR removal. Estrus detection and Al were performed for cows assigned to each protocol during the 144–h synchronized period. There was no difference in estrous response (P = 0.85), interval to estrus (P = 0.09), or variance for interval to estrus (P = 0.75) between treatments, nor were there differences in synchronized conception or pregnancy rates resulting from Al (P = 0.85, P = 0.91, respectively). Experiment 2 was designed to compare pregnancy rates resulting from FTAI after administration of the 7and 5–d CO–Synch + CIDR protocols. Both treatments were administered the same as in Exp. 1; however, cows assigned to the 7–d protocol were inseminated 66 h after PGF2α. and CIDR removal, and cows assigned to the 5–d protocol were inseminated 72 h after the first PGF2c, injection. Cows assigned to both protocols were administered GnRH (100 μg i.m.) at AT. There was no effect of treatment (P = 0.85), technician (P = 0.20), or sire (P = 0.25) on pregnancy rates resulting from FTAI. Given these observations, the 5–d protocol provides an effective alternative to the 7–d protocol for use in facilitating FTAI; however, beef producers must carefully consider the increased labor and treatment costs associated with the 5–d protocol. [ABSTRACT FROM AUTHOR]

Ractopamine-HC1 (RAC) is a 3-adrenergic agonist with variable effects on cattle performance and carcass variables. Cull cows fed RAC (200 mg·head[sup-1]·d[sup-1]) demonstrate an increased size of type I and II muscle fibers that does not translate into a larger ribeye area. The objective of this study was to examine the dose-dependent effects of RAC on cull cow muscle morphometrics. Eighty-eight cull beef cows representing 2 breed types (n = 44 each) were fed 0, 100, 200, and 300 mg·head[sup-1]·d[sup-1] of RAC for the last 28 d of a 54-d feeding period. On d 54, cows were slaughtered, and samples of the LM and semimembranosus muscle (SM) from 16 randomly selected carcasses (n = 4 per treatment) were taken for measurement of 32- adrenergic receptors and type I, IIA, and IIX myosin heavy chain (MyHC) gene expression. Twenty-four hours postmortem, LM, SM, infraspinatus (INF), and vastus lateralis samples from 40 randomly selected carcasses (n = 10 per treatment) were obtained and frozen for immunohistochemical analysis. Muscle fiber cross-sectional area and diameter, MyHC isoform expression, and fiber-associated, nuclei numbers were measured. Ractopamine dosage exhibited differential effects on muscle morphometrics and MyHC gene expression. Muscle fiber cross-sectional area and diameter were increased (P < 0.05) by RAG in INF type I and IIA fibers and SM type IIA fibers. Ractopamine increased (P < 0.05) MyHC type IIX mRNA and tended to increase (P < 0.10) β[sub2]-adrenergic receptors in the SM; a change in mRNA abundance was not detected for either gene in the LM. Treatment with RAG decreased (P < 0.05) fiber-associated nuclei numbers in the INF, vastus lateralis, and LM but did not affect (P> 0.05) MyHG or β-adrenergic receptor expression. These results indicate that cull cow feeding programs may consider supplementing RAG as a means of adding value to cuts within the chuck, such as the INF. [ABSTRACT FROM AUTHOR]

Longissimus muscle area and fat thickness were measured following weaning, at yearling, and prior to harvest using real-time ultrasound, and corresponding carcass measurements were recorded 3 to 7 d following the preharvest scan in composite steers (n = 116, 447 ± 19 d), bulls (n = 224, 521 ± 11 d), and heifers (n = 257,532 ± 12 d). Although fat deposition was limited in bulls and heifers from weaning to yearling, coefficients of variation ranged from 8.46 to 13.46% for muscle area, and from 27.55 to 38.95% for fat thickness, indicating that significant phenotypic variance exists across genders. Residual correlations, adjusted for the effects of year of birth, gender, and age at measurement, were high and ranged from 0.79 to 0.87 among ultrasound and carcass measures of muscle area. Residual correlations among ultrasound and carcass measures of fat thickness were also high, ranging from 0.64 to 0,86. Weaning and/or yearling ultrasound muscle area yielded similarly accurate predictions of carcass muscle area. Yearling ultrasound fat thickness accounted for 13% more of the observed variance in carcass fat thickhess than the weaning ultrasound measure in singletrait prediction models. When both weaning and yearling ultrasound measures were used to predict carcass fat thickness, partial R² values were 0.15 and 0.61 for weaning and yearling ultrasound fat thickness, respectively. The difference between predicted and carcass measures with respect to muscle area (fat thickness) was less than 6.45 cm² (2.5 mm) for 80.2 to 88.9% (90.3 to 95%) of animals. Preharvest ultrasound measures yielded standard errors of prediction of less than 4.95 cm² for muscle area and 1.51 mm or less for fat thickness. These results indicate that ultrasound measures taken between weaning and yearling provide accurate predictors of corresponding carcass traits in steers, bulls, and heifers. [ABSTRACT FROM AUTHOR]

Examines the apparent ruminal degradation and rumen escape of soluble nitrogen fractions in grass and grass silage administered to lactating dairy cows. Accumulation of peptides in rumen after feeding; Ruminal synchronization of nitrogen and energy for microbial growth; Synthesis of microbial protein.

Evaluates the influence of transport stress on the secretion of adrenocorticotropin hormone (ACTH) from peripheral bovine lymphocytes in cows. Experiments on short-term and long-term transport; Use of a highly sensitive and specific sandwich-immunoradiometric assay in ACTH analysis; Indicators of stress in animals.

Presents information on a study which examined the effects of plasma glucose level on the abomasal outflow rate of fluid using a hyperinsulinemic glucose clamp technique in dairy cows. Materials and methods used; Results and discussion; Implications of the study.

Presents a study which determined breed differences in ovarian function and endocrine secretion and daily rectal ultrasonography on multiparious lactating species of cows. Bodily conditions of cows during an estrous cycle in summer; Methodology; Result and discussion; Implications; Conclusion.

Studies the effects of venipuncture on plasma cortisol concentrations in loose-housed dairy cows. Effect of a single venipuncture on plasma concentrations 18 min apart; Anticipatory reaction of cows to once-daily sampling on 6 to 12 successive days; Habituation to serial sampling five times an hour with 2 days in between session.

Determines whether the accuracy, precision and usefulness of prediction equations for estimating yield and composition could be improved when present industry non-fed carcass cutability end points are incorporated in cows. Selection of animal based on confirmation score; Evaluation of carcass characteristics; Collection of compositional data; Analysis using the Greater Linear Method.

The article presents a study which evaluates the influence of flake density on characteristics of ruminal and total-tract digestion in lactating dairy cows fed a high concentrate, corn-based total mixed diet. Topics discussed include information on the decrease milk fat percentage and fiber digestibility; and the discussions on the Steam flaking improving the protein value of corn.

In a 2 x 2 factorial experiment, 110 Holstein cows (55 first-breeding and 55 repeatbreeding), free of genital abnormalities, were injected i.m. at the time of insemination with either saline solution or 100 pg of GnRH. Blood samples were drawn from the tail vein or artery of 22 cows ( 10 firstand 12 repeat-breeding) immediately before GnRH injection and again 1 and 2 h later to determine whether the GnRH induced the release of LH. The GnRH caused LH release in 18 of 22 cows, with a greater (P <

The article focuses on a study conducted to analyze the impact of Synovex C implants on replacement heifers at two different ages. Four different treatments were allotted to crossbred heifers including non-implanted controls, implanted at two months of age and implanted at six months of age, which found that Heifers implanted at two months gained seven kilograms more.

Oxidative stress (OS) is linked to impaired immune and inflammatory responses leading to metabolic and health problems in the transition dairy cow. The aim of the study was to assess the effect of feeding strategy in early lactation on blood and hepatic tissue OS markers in Holstein cows. Eighteen primiparous cows (528 ± 40 kg BW, 3.2 ± 0.2 BCS, fall calving) were used in a randomized block design with two treatments during the first 65 days postpartum (DPP): (G0) total mixed ration (TMR) ad libitum (17 kgDM/d offered; 70% forage:30% concentrate) or (G1) grazing of alfalfa (Medicago sativa; 6-h am grazing in 3-d strips; pasture allowance = 20 kgDM/d) + TMR (70% of ad libitum TMR). Both groups consumed 2.2 kg DM/d of a commercial ration at each milking. Cows were milked twice a day and milk yield was recorded daily. Cow BCS was recorded and blood samples and hepatic biopsies were collected at -7 and +42 ± 3 DPP. Production of reactive oxygen substances (ROS; d-ROMs Test, Diacron, Italy) and antioxidant capacity (SAC; OXY-Adsorbent Test, Diacron) were determined in serum and OS index (OSi) was calculated (ROS/SAC). Expression of 4-hydroxynonenal (4-HNE) modified proteins in liver homogenates was analyzed by Western blotting. Data were analyzed as repeated measures with a mixed model including DPP and feeding strategy within DPP as fixed effects and block as random effect. Milk yield was greater (27.5 vs. 25.6 ± 0.60 kg/d; P = 0.03) while BCS loss from -7 to +42 DPP was less (-0.50 vs. -0.75 ± 0.03; P = 0.04) for G0 than G1 cows. Serum ROS production tended to decreased from -7 to +42 DPP (268.4 vs. 244.6 ± 9.7 CarrU; P = 0.058). All cows during the pre and postpartum periods, had SAC values lower than 350 µmol HClO/mL indicating an impairment of serum antioxidant barrier. However, SAC decreased from -7 to +42 DPP only in G1 cows (298.2, 278.8 and 304.4 ± 6.3 µmol HClO/mL for -7 DPP and G0 and G1 at 42 DPP, respectively; P = 0.011). Thus, during the postpartum, serum OSi tended to be greater (P = 0.09) for G1 than G0 cows (0.92 vs. 0.80 ± 0.05 CarrU/µmol HClO.mL-1). Presence of 4-HNE in the liver increased from -7 to +42 DPP only in G1 cows (0.73 ± 0.21 and 1.31 vs. 0.81 ± 0.16 for -7 DPP and G0 and G1 at 42 DPP, respectively; P = 0.014). Oxidative stress increased during the postpartum in G1 cows associated to a more severe negative energy balance. [ABSTRACT FROM AUTHOR]

A combination of direct injection and tandem mass spectrometry with a reverse-phase liquid chromatography and tandem mass spectrometry was used to detect serum metabolite signatures in 20 cows that expelled their fetal membranes normally and 6 cows that retained placenta. We aimed to identify serum biomarkers that can predict the risk of retained placenta (RP) in transition dairy cows. Blood samples were obtained from the coccygeal vein once per week at 0700 h before the morning feeding at 8 and 4 wk before parturition, at the week of RP, and at 4 and 8 wk postpartum. We studied perturbation of serum metabolites using an AbsoluteIDQ 180 kit (BIOCRATES Life Science AG, Innsbruck, Austria), which contained metabolites related to AA, acylcarnitines, biogenic amines, glycerophospholipids, sphingolipids, and hexose. Univariate analysis of data was performed using Wilcoxon-Mann-Whitney test provided by R (version 3.0.3; 2008). Metabolomic data were analyzed using the MetaboAnalyst software. Statistical significance was declared at P < 0.05. Results showed that cows with RP were characterized by a decrease in lysophosphatidylcholine (LysoPC) a C18:2, C20:3, C20:4, C28:0, and C28:1 at 8 wk before parturition and during the week of diagnosis of RP (P < 0.01). At 4 wk prior to calving, LysoPC a C20:4 and C28:0 were decreased. Concentrations of phosphatidylcholines (PC) changed after calving, with 12 and 4 species of PC elevated at 4 and 8 wk after calving, respectively (P < 0.05). Cows with RP were characterized by increased concentrations of sphingomyelins in the serum at 8 wk prior to parturition (P < 0.05), the week of RP (P < 0.05), and at 4 and 8 wk after parturition (P < 0.05). Amino acids Lys, Ile, and Leu were greater in cows diagnosed with RP during all experimental time. Biogenic amines, acetylornithine, asymmetric dimethylarginine, total dimethylarginine, carnosine, creatinine, and sarcosine were greater in RP cows during diagnosis week (P < 0.01). It is intriguing that pre-RP, RP, and post-RP cows showed an increased concentration of Lys, Ile, Leu, and acetylornithine during all experimental time points studied (P < 0.01). Moreover, LysoPC a C20:4 and C28:0, ornithine, and Asn decreased before parturition and at the disease diagnosis week (P < 0.05). In conclusion, RP is preceded by and associated with alterations in multiple species of AC, PC, LPC, AA, and BA starting from 8 wk prior to parturition. Alterations of serum Lys, ornithine, acetylornithine, LysoPC a C28:0, Asp, Leu, and Ile might be novel serum biomarkers for prediction of risk of RP in dairy cows. [ABSTRACT FROM AUTHOR]

The objective of this research was to establish postprandial patterns of eating in lactating dairy cows on diets based on either solely barley grain or a choice of multiple grains. Eight multiparous (642 kg [SD 57] BW and 72 d [SD 58] in milk) lactating Holstein cows were studied in a crossover design experiment with two 21-d periods. Cows were housed and managed in free individual boxes and fed alfalfa hay-corn silage-based total mixed rations with either barley as the only grain (BR) or a mixture of barley, corn, wheat, and sorghum (MG). Proportion of cereals in the multigrain treatment was equal, each equal to 25%. Grains were included as 30% of total dietary DM. Diets were prepared as total mixed rations and offered for 5 to 10% daily orts. Cows were fed at 0530, 1330, and 2130 h. Feed intake and eating rate were continuously monitored for the entire experiment and collected for data analysis during the third week of both periods. Feed intake patterns were expressed every 3 h after feeding as a percentage of total daily intake. Statistical data analysis was conducted with Mixed Models procedures of the SAS program (SAS Inst. Inc., Cary, NC). Feeding MG vs. BR increased eating rate shortly after feeding (P < 0.05), such that MG and BR cows consumed 80 and 73%, respectively, of their daily total mixed ration intake within the first 3 h after feeding, summing all feeding occasions. Based on individual data, some cows in the MG group consumed up to 90% of their total daily intake within only 3 h after feeding. These suggest a stronger craving for fresh feed in MG cows compared with BR cows, which could indicate improved feed palatability when multigrain rather than solely barley grain was fed. Total daily feed intake was greater for MG vs. BR (21.2 vs. 19.9 kg/d; P < 0.05). These results suggest that type/mixture of starch is a determinant of circadian eating patterns and influences voluntary feed intake regulation in lactating dairy cows. Because eating behavior patterns determine circadian patterns of rumen metabolism and peripheral substrate availability, findings on the superiority of MG over BR in stimulating the cow craving for fresh feed provide metabolic and health implications. [ABSTRACT FROM AUTHOR]

The crucial role of rumen and hindgut microbiomes in intestinal and extra-intestinal diseases is emerging. Both rumen and hindgut microbiomes have been shown to impact host physiology, metabolism, and immune function and to confer direct and indirect (immune-mediated) resistance against enteric pathogens. Disruption of rumen and hindgut microbiomes or dysbiosis - which is referred to as an abnormal balance of beneficial and protective versus opportunistic members of microbiota - have been linked to a number of metabolic disorders that occur around early to mid-lactation periods, such as acute and subacute ruminal acidosis, milk fat depression, and bloat. Dysbiosis of the gut microbiome impacts the profile of microbially-driven metabolites and compounds produced by the microbiota. These molecules influence the metabolic and immunological capacities of the host both within and outside of the gut, e.g. through the enterohepatic pathway or the gut-brain axis, which retroactively impacts the diversity and behaviour of the microbiome in the digestive tract, and also potentially influences the microbiomes of other body sites, such as vaginal tract or mammary gland resulting in initiation or progression of infectious or inflammatory diseases in those systems, e.g. mastitis. The research by our group and others shows that interactions among commensal members inhabiting different ecological niches of the udder (i.e. teat apex, teat canal, and milk) are crucial for shaping the composition and functional properties of the mammary gland microbiome, and potentially govern the susceptibility of dairy cows to infectious mastitis. Similarly, a healthy vaginal microbiome has a key role in improving ruminants' reproductive performance and preventing infectious diseases. It is thus speculated that nutritional and physiological stressors at early lactation, which are one of the significant underpinnings of the microbiome-gut-brain axis, not only impact the diversity and behavior of the gastrointestinal tract microbiome but also the vaginal and mammary gland microbiomes and thus susceptibility to infectious diseases. In this presentation, I will review the role of rumen and hindgut microbiomes in the context of their association with vaginal tract and mammary microbiomes in dairy cows subjected to subacute ruminal acidosis during early lactation. I will also highlight the pressing need for development of synthetic microbial communities to improve gut, mammary and vaginal health and production efficiency of ruminant animals. [ABSTRACT FROM AUTHOR]

Cattle breeding difficulties across the Southern United States are often attributed to heat stress. Additional factors including mycotoxin consumption may negatively impact reproductive performance. Zearalenone (ZEN) is a mycotoxin associated with reproduction-related effects due to its estrogenic activity. Recent research has identified ZEN contamination in pastures in South Central Florida. A trial was conducted at a commercial ranch in South Central Florida to evaluate the effects of Biofix® Plus PRO (Biomin Holding GmbH, Austria) supplementation in a free-choice molasses-based liquid feed product (Westway Feed Products) on the performance of cow-calf pairs. Cows were randomly assigned to one of two treatment groups: Control (n = 194) or Treatment (n = 206). Liquid feed was provided ad libitum from December 2015 through October 2016 with the formulation adjusted over time to maintain intake goals. Biofix® Plus PRO was supplemented to the Treatment group at an intended rate of 30 gram/head/day during the breeding period (December through April) and reduced to 15 gram/head/day through October. Bulls were with cows from January through early April. Calves from the previous calving season were weaned in June. Treatment group calves weighed on average 24.0 kg more than calves in the Control group. Individual calf weights were not obtained in this commercial facility. All cows were screened for pregnancy status (Control = 91.2% bred; Treatment = 90.3% bred; Z-score P = 0.741) at weaning. Every fourth confirmed pregnant cow per group was identified for future pregnancy status evaluation (51 cows per group) and body condition score (BCS) determination (Control = 5.1 ± 0.1 SEM; Treatment = 5.9 ± 0.1 SEM; Unpaired t-test P < 0.0001). After 47 days, pregnancy status (Control = 100% bred; Treatment = 96% bred; Z-score P = 0.162) and BCS (Control = 5.4 ± 0.1 SEM; Treatment = 6.1 ± 0.1 SEM; Unpaired t-test P < 0.0001) were re-evaluated. Two Control cows (1 culled; 1 not caught) were not evaluated. One Treatment cow had calved prematurely and another was estimated to have lost her calf following the first pregnancy screen. Live calf crop from tagged cows (Control = 96% Treatment = 90%; Z-score P = 0.230) was determined in February 2017. One Control cow culled during the trial period and two Treatment cows identified as open in August were not included in calf crop calculations. Biofix® Plus PRO supplementation of molasses-based liquid feed significantly increased BCS in cows and increased weaning weights of calves in cow-calf pairs grazing pastures in South Central Florida. [ABSTRACT FROM AUTHOR]

Our objective was to evaluate the effects of two herbage allowance (HA) on forage mass (FM), Insulin and IGF-1 concentrations of primiparous beef cows. Thirty two spring calving cows were allocated to a completely randomized block design of two blocks and two HA from -150 to 185 days postpartum (DPP). Treatments (ratio between FM and stocking rate) fluctuated throughout seasons: autumn 5 and 3, winter 3 and 3, spring and summer 4 and 2 kg forage DM/kg liveweight for high and low HA, respectively. Put-and-take was employed to adjust HA and FM was measured seasonally via the comparative yield method. Blood samples were collected -90 (autumn), -50, -20 (winter), 20, 50 (spring), 85, 185 DPP (summer). Forage mass, Insulin, IGF-I were analyzed using mixed models and means were compared using Tukey. High HA had greater FM than low (P = 0.04; Table 517) and was not affected by HAxDPP (P = 0.35). The FM decreased slightly in winter and then increased 3-fold in summer. Insulin was affected by DPP (P < 0.001; Table 517) but not by HA (P = 0.31) and HAxDPP (P = 0.21). Insulin decreased until 20 DPP, increased at 50 DPP and decreased again. Insulin increased 2-fold from 85 until 180 DPP. Seasonal changes in Insulin concentrations can be explained by forage intake associated to FM. The IGF-1 were greater in high than low HA at -90 but no other differences were identified (HAxDPP, P < 0.007; Table 517). The IGF-1 decreased from -90 to -20 DPP, then increased to 50 DPP and remained constant until 185 DPP. Forage mass differences between treatments at -90 DPP and the low cow energy requirements could explain the improvement in IGF-1 in high HA. Herbage allowance affected the energy metabolism of primiparous beef cows grazing Campos. [ABSTRACT FROM AUTHOR]

At the udder level, increasing the milk flow rate at which milking is terminated, shortens milking time and increases milking efficiency in automatic milking systems (AMS). It is hypothesized that this can be improved upon by setting the milk flow rate at the udder quarter level, regardless of feed availability. The objective of this study was to investigate the effect of udder quarter level milk flow rates (0.06, 0.3, or 0.48 kg/min) applied with or without teaser feed on milking time, milk yield, SCC and the degree of udder emptying, of cows in a FeedFirst™ AMS system. Thirty cows were assigned to six groups, balanced by parity (2.9 ± 1.5), days in milk (142 ± 25 d), and production (34.0 ± 11.7 kg/d). All cows had SCC < 115.000 cells/ml when enrolled. Cows were exposed to treatments for 7d using a 3×2 factorial arrangement within a 6×6 Latin square. Data on milk yield, milking time and interval were automatically collected by the AMS. Milk samples for SCC were collected at the udder level during the last 2 d of each period. Udder-level residual milk yield was sampled on the last milking during periods 1, 3, and 5. For harvesting residual milk, cows received an intramuscular injection of oxytocin (70 I.U., Partoxin™ vet) and milking was initiated again 3 min after the injection using a bucket milking machine. The data were analyzed by ANOVA in a linear mixed-effects model using repeated measures in SAS (v9.4). Teaser feed was found non-significant for all response variables. Milking interval for the study was below 8 hours for all treatments and was not affected by take-off level or teaser feed (P > 0.05). Milking time was shortest for 0.48 (6.7 ± 0.5 min) and increased with lower take-off levels (P < 0.05): 7.2±0.5 min for 0.3 and 7.6 ± 0.5 min for 0.06. Milking time was not affected by teaser feed or the interaction of take-off level × feed. No treatment effect or interaction was evident for milk yield, residual milk yield, residual milk yield as % of total milk, or SCC (P > 0.05). In conclusion, milking efficiency in AMS can be improved by applying a take-off level of 0.48 kg/min on udder quarter level without losing milk yield or increase SCC. An effect of teaser feed on udder emptying could not be demonstrated in this study, indicating that teaser feed is less important when cows are directed through the feeding area before milking. [ABSTRACT FROM AUTHOR]

The objective of this study was to evaluate growth of the dominant follicle (DF) in multiparous Nellore cows treated with equine chorionic gonadotropin (eCG) either 4 or 2 d prior to timed AI (TAI). We hypothesized that early eCG administration improves follicular growth and increase DF diameter at TAI. Cows (n = 137) had their estrous cycle synchronized with an intravaginal device containing 1.9 g of progesterone (CIDR) and 2.0 mg of estradiol benzoate (d 0), 12.5 mg of PGF2a (d 7), CIDR withdrawal and 0.3 mg of estradiol cypionate (d 9), and TAI 48 h later (d 11). On d 7, ovaries were evaluated by ultrasonography and cows were blocked based on DF diameter (< 9 mm vs. ≥ 9 mm). Within block, cows were randomly assigned to receive 300 IU of eCG either on d 7 (eCGD7; n = 64) or on d 9 (eCGD9; n = 73). Diameter of the DF was evaluated by transrectal ultrasonography on d 7, 9, and 11. Follicular growth from d 7 to 9, 7 to 11, and 9 to 11 was analyzed by ANOVA using the GLIMMIX procedure of SAS. Follicular diameter was analyzed by ANOVA for repeated measures and cow was considered a random effect. Follicular growth from d 7 to 11 tended to be greater (P = 0.08) for eCGD7 compared with eCGD9 (4.9 ± 0.2 vs. 4.4 ± 0.2 mm). The overall effect of treatment was explained mostly by DF growth from d 7 to 9 (eCGD7 = 2.6 ± 0.2 vs. eCGD9 = 2.0 ± 0.2 mm; P < 0.01) as growth from d 9 to 11 did not differ (P = 0.44) between treatments (eCGD7 = 2.3 ± 0.2 vs. eCGD9 = 2.4 ± 0.1 mm). Follicular diameter was affected (P < 0.01) by the interaction between treatment and day. Whereas no difference was observed on d 7 (eCGD7 = 9.7 ± 0.2 vs. eCGD9 = 9.6 ± 0.2 mm), DF in eCGD7 cows was larger (P < 0.01) on d 9 (12.3 ± 0.2 vs. 11.5 ± 0.2 mm). In addition, DF on d 11 did not differ (P = 0.12) between treatments (eCGD7 = 14.5 ± 0.3 vs. eCGD9 = 14.0. ± 0.2 mm). Treatment with 300 IU of eCG 4 d prior to TAI improved follicular growth but did not increase overall mean of DF diameter at TAI compared with eCG administration 2 d before TAI in Nellore cows. [ABSTRACT FROM AUTHOR]

To investigate a potential relationship between animal temperament and mitochondrial function, 5-yr-old Brahman cows were stratified into one of three temperament groups based on herdsman scores: T1 (n = 4; calm), T2 (n = 4; normal), or T3 (n = 4; temperamental). The cows were processed at the departmental meats lab and samples from the longissimus dorsi (LD) and semitendinous muscles were collected. All samples were assessed for mitochondrial density (via citrate synthase activity) and function (via cytochrome c oxidase activity); samples from the LD were also evaluated for mitochondrial capacity utilizing high-resolution respirometry. Data were analyzed using the MIXED procedure of SAS (9.4). Relative to mg of tissue (integrative mitochondrial capacity), temperamental cattle (T3) had greater state 3 oxidative phosphorylation capacity with complex I substrates (PCI), PCI plus complex II substrates (PCI+II), maximum electron transport capacity (ECI+II), and ECII than T1 (P = 0.009, P = 0.03, P = 0.02, and P = 0.04 for PCI, PCI+II, ECI+II, and ECII, respectively) or T2 (P = 0.03, P = 0.02, P = 0.03, and P = 0.03 for PCI, PCI+II, ECI+II, and ECII, respectively). Temperamental cattle (T3) also had a higher fractional control ratio of PCI+II (0.890 ± 0.023) than T2 (0.780 ± 0.025; P = 0.02), with T1 being intermediate (0.814 ± 0.023). This indicates a greater contribution of complex II to oxidative phosphorylation and energy production in temperamental animals, the effects of which are unknown at this time. Temperamental animals (T3) also had the greatest citrate synthase activity across muscle groups (9.49 ± 0.70 nmol/min*mg tissue) compared to T1 (6.44 ± 0.68; P = 0.009) or T2 (5.29 ± 0.59; P = 0.0008), indicating greater skeletal muscle mitochondrial density in T3. Intrinsic mitochondrial capacity (relative to CS activity) and cytochrome c oxidase activity (mitochondrial function) were not different between muscles, nor between temperament groups. Research is needed to clarify the significance of different patterns of energy production in temperamental cattle. Further, skeletal muscle mitochondrial capacity may be a useful early indicator of animal performance and carcass quality at harvest. [ABSTRACT FROM AUTHOR]

Ketotic cows have elevated concentrations of ketone bodies or ketoacids (i.e., b-hydroxybutyric acid [BHBA], acetoacetic acid [AcAc], and acetone) in 3 body fluids including blood, urine, and milk. Both BHBA and AcAc are strong acids that cause ketoacidosis and affect physiological functions of various tissues. The objectives of the current study were to 1) investigate mineral alterations in both serum and urine of preketotic, ketotic, and postketotic cows and 2) identify potential predictive and diagnostic mineral biomarkers for ketosis in serum and urine. Metallotyping was performed in the serum and urine of 6 cases of ketosis and 20 control cows using inductively coupled plasma mass spectrometry at -8 and -4 wk, disease diagnosis week, and +4 and +8 wk relative to parturition. Univariate analysis of data was performed using the Wilcoxon-Mann-Whitney (rank sum) test provided by R (statistical significance: P < 0.05). Multivariate data analysis was processed by the MetaboAnalyst software. Results showed disturbances in concentrations of metals in the serum and urine of cows with ketosis at all 5 time points tested. The most important finding of this study was that 4 trace elements including Al, Fe, Mn, and As were persistently elevated in the serum of preketotic, ketotic, and postketotic cows. Moreover, 3 minerals (i.e., B, Al, and Rb) were increased in the urine of preketotic (8 and 4 wk prepartum) cows. It is interesting to point out that Al was the most elevated metal in the serum of preketotic cows at 8 and 4 wk prior to parturition at 91.4-fold (120.6 vs. 1.32 µM) and 78.12-fold (111.34 vs. 1.43 µM), respectively (P < 0.001). Similar alterations for Al were also detected in the urine samples of preketotic (i.e., 0.39 vs. 0.05 µM/mM creatinine at -8 wk [P < 0.001] and 0.16 vs. 0.05 µM/mM creatinine at -4 wk [P < 0.001]) cows in comparison with control cows. Because preketotic and ketotic cows were on a state of chronic metabolic acidosis, altered mineral elements in both serum and urine are thought to be related to the effects of acidosis on bone metabolism and urine excretion of metals. Findings from the current study might encourage development of early diagnostic biomarkers for risk of ketosis as well as new preventative intervention to lower the risk of ketosis in transition dairy cows. [ABSTRACT FROM AUTHOR]

The objective of this experiment was to establish postprandial patterns of eating rate in once-daily-fed high-producing lactating dairy cows. Eight multiparous (664 kg [SD 62] BW and 80 d [SD 40] in milk) lactating Holstein cows were studied in a crossover design experiment with two 21-d periods. Cows were kept under thermoneutral conditions and offered an experimental total mixed ration (TMR) based on barley and corn grains, corn silage, and alfalfa hay, as the main starch and forage sources, at either 0800 or 2000 h The forage-to-concentrate ratio on a DM basis was 50:50, offered for 5 to 10% daily oris. Feed intake was continuously monitored for the entire experiment and collected for data analysis during the third week of both periods. Statistical data analysis was conducted with Mixed Models procedures of SAS (SAS Inst. Inc., Cary, NC) program. Feed intake patterns were expressed every 3 h as a percentage of total daily intake. Feeding the TMR at 2000 vs. 0800 h increased eating rate shortly after feeding (P < 0.05), such that morning-fed and evening-fed cows consumed 33 and 45%, respectively, of their daily TMR intake within the first 3 h after feeding. However, within 9 h after feeding, morning-fed (72%) and evening-fed (74%) cows ate comparable amounts of their total daily intake (P > 0.15). Based on individual data, some cows in the evening-fed group consumed up to 70% of their total daily intake within only 3 h after feeding. Total daily intake, however, was similar between morning-fed (21.2 kg) and evening-fed (21.4 kg) cows (P > 0.15). These results demonstrated that timing of feeding as an external modulator of circadian ruminant physiology significantly contributes to rhythmic regulation of feed intake patterns. Findings provide implications for effective farm management of high-producing cows exposed to various metabolic challenges. [ABSTRACT FROM AUTHOR]

Discusses the abstract of the study 'Cow muscle profiling: Comparison of processing traits and shear forces of 21 muscles from beef and dairy cow carcasses,' presented at the American Society of Animal Science's Midwestern Branch conference on March 17-19, 2003, in Des Moines, Iowa.

Presents an abstract of the research titled `Circulating Progesterone and Intrafollicular Steroid Concentrations in Dominant Ovarian Follicles Following an Injection of Progesterone in Cows,' by B.R. Lindsey, M.E. Wehrman, et al. Determination of effects of a single injection of progesterone at different times.

Presents an abstract of the research titled `The Effect of Duration of Nutritional Anestrus and GnRH Treatment on Pituitary LH, FSH and GnRH Receptors in Cows,' by J.A. Vizcarra, R.P. Wettemann, and T.D. Braden. Utilization of twenty-four nutritionally anestrous cows.

Presents an abstract of the research titled `Effects of Passive Immunization Against Inhibin on Follicle-Stimulating Hormone Concentrations and Litter Size in Cows,' by J.E. Wheaton, R.L. Meyer, et al. Determining whether passive immunization against inhibin at weaning would increase follicle-stimulating hormone secretion.

Presents an abstract of the research titled `Fertility of Synchronized Cows After Gonadotropin-Releasing Hormone and Timed Insemination,' by D.W. Forrest, J.S. Bluntzer and P.G. Harms. Comparison of fertility following a timed insemination with fertility following insemination based on observed estrus in synchronized cows.