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The present study aimed to evaluate the effects of different supplemental fat sources (soyabean oil (SBO) as a source of n-6 fatty acid (FA) and fish oil (FO) as a source of n-3 FA) in the starter feed of milk-fed dairy calves during the hot season. Forty Holstein calves (3 d of age; 39·67 kg of body weight; ten calves per group) were randomly assigned to the experimental treatments as follows: (1) starter feed supplemented with no fat source (CON), (2) starter feed supplemented with 3 % SBO (DM basis), (3) starter feed supplemented with 3 % FO (DM basis) and (4) starter feed supplemented with an equal mixture of SBO and FO (1·5 % each, DM basis). The milk feeding schedule was constant for treatments and all calves were weaned on day 65 of age. Results show that calves had greater starter intake, average daily gain and body length when fed SBO compared with the other treatments. However, feed efficiency was increased and inflammatory indicators (TNF-α, serum amyloid A and haptoglobin) concentrations were reduced in the calves fed FO compared with the other treatments. In summary, it was revealed that SBO rich in n-6 FA improved starter intake and growth performance, while FO rich in n-3 FA could improve the immune function of calves. Due to the current experimental condition, an equal mixture of SBO and FO (1·5 % each, DM basis) can be recommended to have an optimum growth performance and immune function while the calves are reared under the heat conditions. [ABSTRACT FROM AUTHOR]

Stressful situations may result in serum chromium (Cr) depletion with increased urinary excretion of the mineral and increased Cr requirements. The objective of this study was to investigate the effects of Cr supplementation on growth performance, feeding behavior, blood metabolites and hormones, indicators of oxidative stress and glucose-insulin kinetics of summer-exposed weaned dairy calves. In total, 48 Holstein female calves (63 days of age; 77.0±1.45 kg of BW) were assigned randomly to one of two treatments: (1) a control group with no supplemental Cr (Cr−), and (2) a supplemental Cr group (Cr+) to supply 0.05 mg Cr as Cr-methionine/kg of BW0.75. Chromium was provided in the starter feed and adjusted weekly based on BW over the experimental period. All calves were on experiment for 4 weeks after weaning. The average maximum temperature–humidity index was 76.1 units during the study period, indicating a mild degree of environmental heat load. Results indicated that in summer-exposed dairy calves, increased dietary Cr provision tended to decrease fecal score, tended to change rumination pattern, increased antioxidant capacity by increasing serum concentration of catalase, but had no effects on growth performance, metabolic status or peripheral glucose and insulin metabolism. [ABSTRACT FROM AUTHOR]

The objective of this study was to investigate the effects of extruded full-fat soybean (ESB) as a replacement for soybean meal (SBM) on nutrient intake, rumen fermentation, and growth performance of dairy calves. A total of 45 male Holstein dairy calves (42.0±0.5 kg of BW) were randomly assigned to one of three experimental diets: (1) 0% ESB (Control): 35.3% SBM no ESB; (2) 25% ESB: 27.0% SBM+9.0% ESB; and (3) 50% ESB: 19.0% SBM+19.0% ESB. All calves were weaned on day 56 of age and remained in the study until day 70 of age. During the pre-weaning and overall periods, substituting of SBM with ESB had no effect on intake of starter feed, metabolizable energy (ME), CP and non-fiber carbohydrate (NFC). Compared with the control, 50% ESB resulted in a decrease in starter feed intake, and intakes of other nutrients including CP, NFC and ME during the post-weaning period. Substituting SBM with ESB decreased intake of C16 : 0 and increased intakes of n-9 C18 : 1, n-6 C18 : 2 and n-3 C18 : 3 during the pre-weaning, post-weaning and overall periods. Using ESB as a replacement for SBM did not affect average daily gain, feed efficiency, rectal temperature and fecal score over the trial periods. Compared with control, the rumen concentration of NH3-N decreased for 50% ESB on days 35 and 56 of age but not when compared with 25% ESB. Rumen pH, total volatile fatty acids concentrations, and the molar proportions of ruminal acetate, propionate and butyrate were not different among treatments. Body measurements were not affected by the treatments. In conclusion, substitution of SBM with ESB may improve nitrogen utilization efficiency in dairy calves but slightly reduce post-weaning starter intake with no negative outcomes on growth performance and rumen fermentation. [ABSTRACT FROM PUBLISHER]

Two experiments were conducted to determine the effects of feeding equal quantities of milk during the pre-weaning period through different milk-feeding regimes on calf growth, starter intake and selected blood metabolites. In experiment 1, 44 female Holstein calves (3 days of age and 39.2±4.3 kg of BW) were distributed randomly to one of two milk-feeding programs (1 calf per pen; 22 pens per treatment group): (1) consistent (CONS; 6 l/day of milk from days 3 to 60 and 3 l/day from days 61 to 65 of age) or (2) step-up/step-down (SUSD; 5 l/day of milk from days 3 to 15, 8 l/day from days 16 to 40, 6 l/day from days 41 to 50, 3 l/day from days 51 to 60 and then 2 l/day from days 61 to 65 of age). No difference between treatments was observed in starter consumption, feed efficiency, hip width and heart girth. However, pre-weaning average daily gain (ADG) tended to be greater in CONS than in SUSD calves (0.78 v. 0.70 kg/day; P=0.07). Blood β-hydroxybutyrate at day 45 (pre-weaning) was lower in SUSD than in CONS calves (0.14 v. 0.21±0.013 mmol/l). In experiment 2, 26 male Holstein calves (3 days of age and 39.4±4.1 kg of BW) were assigned at random to one of two milk-feeding protocols (1 calf per pen; 13 pens per treatment group): (1) consistent (CONS; (7 l/day of milk from days 3 to 40 and 2 l/day from days 41 to 45 of age) or (2) step-down (STD; 8 l/day of milk from days 3 to 30, 4 l/day from days 31 to 40 and 2 l/day from days 41 to 45 of age). The milk-feeding program had no effect on the performance measurements, with the exception that ADG (days 15 to 30), starter intake (days 30 to 45) and heart girth (day 45) were greater in STD than in CONS calves. In conclusion, it appears that if the total amount of milk intake is held constant over the course of milk-feeding period, the method of milk feeding would have negligible effects on calf performance. [ABSTRACT FROM PUBLISHER]

This study evaluated the effects of physical form of starter feed and forage provision on the performance, blood metabolites, liver composition and intestinal morphology of dairy calves. Individually housed calves ( n = 52; body weight = 41.5 ± 2.5 kg) were randomly allocated ( n = 13 per treatment) to one of the following four treatments: (i) ground starter feed (GS; mean particle size = 0.72 mm in diameter), (ii) textured starter feed (TS; mean particle size = 3.61 mm in diameter, including steam-flaked corn and barley), (iii) pelleted starter feed (PS; mean particle size = 4.53 mm in diameter) and (iv) ground starter feed with chopped alfalfa hay (GS + AH; mean particle size = 1.02 mm in diameter). The calves fed GS + AH diets had greater (p < 0.01) starter intake, final body weight and average daily gain compared with the other groups, while GS and TS groups both had greater (p < 0.01) starter intake than the PS group. Feed efficiency was found to be better (p < 0.05) in the TS group than in the GS or PS group, but not different from the GS + AH one. Compared with the other groups, the GS + AH group had the highest (p < 0.01), while the PS one had the lowest (p < 0.01) concentrations of blood glucose and triglyceride. The calves fed GS + AH had the highest blood concentrations of total protein, globulin, triiodothyronine (T3), thyroxin (T4), T3 : T4 ratio (p < 0.05) and levels of fat and glycogen in the liver (p < 0.01) compared with the other groups. The highest (p < 0.05) liver glycogen contents were observed in the GS + AH and TS groups. The duodenum, ileum and jejunum in the calves fed GS + AH exhibited a greater muscle layer thickness (p < 0.05) compared with the other groups. Based on the results obtained, the addition of dietary forage to starter diets positively influenced performance, liver composition and intestinal morphology in developing calves. [ABSTRACT FROM AUTHOR]

A lactation experiment was conducted to determine the influence of addition of pistachio by-products extract ( PBE) to alfalfa silage ( AS) on performance, rumen fermentation, milk yield and composition, and microbial nitrogen synthesis. Eight multiparous dairy goats (1.8 ± 0.25 kg of milk yield) were used in a replicated 4 × 4 Latin square design with a 2 × 2 factorial arrangement of treatments to compare two types of AS (supplemented with or without PBE) with two levels of dietary crude protein (14% vs. 16% CP). Dietary treatments were (i) AS with 14% CP of DM diet without PBE (14% CP− PBE), (ii) AS with 14% CP of DM diet with PBE (14% CP + PBE), (iii) AS with 16% CP of DM diet without PBE (16% CP− PBE) and (iv) AS with 16% CP of DM diet with PBE (16% CP + PBE). PBE was sprayed on fresh alfalfa at a ratio of 500 ml/kg alfalfa DM to get the final concentration of 1% tannin as tannic acid equivalent on DM basis. Intake of CP was greater (p < 0.01) in goats fed 16% CP diets than those fed 14% CP diets, regardless of PBE supplementation. Supplementation of PBE tended to decrease (p = 0.09) rumen NH3-N concentration regardless of the level of CP in the diet. Supplementation of PBE tended (p = 0.09) to decrease total purine derivatives regardless of the level of CP in the diet with no significant change in microbial nitrogen supply. Efficiency of microbial nitrogen synthesis ( EMNS) had a tendency (p = 0.07) to decrease in PBE supplemented diets. There was also a tendency (p = 0.10) for more EMNS in 14% CP fed goats than those fed 16% CP diets. Therefore, AS supplemented with PBE may lead to less concentration of ruminal NH3-N because of decreased degradation of CP by rumen micro-organisms in response to pistachio by-products tannins. [ABSTRACT FROM AUTHOR]

A meta-analysis of the potential effect of forage provision on growth performance and rumen fermentation of dairy calves was conducted using published data from the literature (1998-2016). Meta-regression was used to evaluate the effects of different forage levels, forage sources, forage offering methods, physical forms of starter, and grain sources on the heterogeneity of the results. We considered 27 studies that reported the effects of forage provision to dairy calves. Estimated effect sizes of forage were calculated on starter feed intake, average daily gain (ADG), feed efficiency (FE), body weight (BW), and rumen fermentation parameters. Intake of starter feed, ADG, BW, ruminal pH, and rumen molar proportion of acetate increased when supplementing forage but FE decreased. Heterogeneity (the amount of variation among studies) was significant for intake of starter feed, ADG, FE, final BW, and rumen fermentation parameters. Improving overall starter feed intake was greater in calves offered alfalfa hay compared with those offered other types of forages. During the milk feeding and overall periods, improving ADG was greater for calves fed a high level of forage (>10% in dry matter) compared with those fed a low level of forage (≤10% in dry matter) diets. The advantages reported in weight gain at a high level of forage could be due to increased gut fill. Improving overall ADG was lower for calves offered forages with textured starter feed compared with ground starter feed. The meta-regression analysis revealed that changes associated with forage provision affect FE differently for various forage sources and forage offering methods during the milk-feeding period. Forage sources also modulated the effect of feeding forage on ruminal pH during the milk-feeding period. In conclusion, forage has the potential to affect starter feed intake and performance of dairy calves, but its effects depend on source, level, and method of forage feeding and physical form of starter feed independently of grain sources included in the starter feed. [ABSTRACT FROM AUTHOR]

The objective of this study was to investigate the effects of grain sources and forage provision on growth performance, blood metabolites, and feeding behaviors of dairy calves. Sixty 3-d-old Holstein dairy calves (42.2 ± 2.5 kg of body weight) were used in a 2 × 3 factorial arrangement with the factors being grain sources (barley and corn) and forage provision (no forage, alfalfa hay, and corn silage). Individually housed calves were randomly assigned (n = 10 calves per treatment: 5 males and 5 females) to 6 treatments: (1) barley grain (BG) without forage supplement, (2) BG with alfalfa hay (AH) supplementation, (3) BG with corn silage (CS) supplementation, (4) corn grain (CG) without forage supplement, (5) CG with AH supplementation, and (6) CG with CS supplementation. All calves had ad libitum access to water and starter feed throughout the experiment. All calves were weaned on d 49 and remained in the study until d 63. Starter feed intake and average daily gain (ADG) was greater for calves fed barley than those fed corn during the preweaning and overall periods. Calves supplemented with CS had greater final body weight and postweaning as well as overall starter feed intake than AH and non-forage-supplemented calves. During the preweaning and overall periods, feeding of CS was found to increase ADG compared with feeding AH and nonforage diets. However, feed efficiency was not affected by dietary treatments. Calves supplemented with CS spent more time ruminating compared with AH and control groups; nonnutritive oral behaviors were the greatest in non-forage-supplemented calves. Regardless of the grain sources, the rumen pH value was greater for AH calves compared with CS and non-forage-supplemented calves. Blood concentration of BHB was greater for CS-supplemented calves compared with AH and non-forage-supplemented calves. Furthermore, body length and heart girth were greater for calves fed barley compared with those fed corn, and also in forage-supplemented calves compared with nonforage-supplemented calves. These results showed no interactions between grain sources and forage provision on calf performance; however, the inclusion of CS and barley in starter diets could enhance the growth performance of Holstein calves during the transition from liquid to solid feed. [ABSTRACT FROM AUTHOR]

Previous research has shown that both sunflower seed (SF) and sucrose (SC) supplementation can result in variation in milk fat concentration and composition, possibly due to altered fermentation patterns and biohydrogenation of fatty acids in the rumen. The objective of this study was to determine the effects of different sugar concentrations with or without SF supplementation on lactation performance, ruminal fermentation, and milk fatty acid profile in lactating dairy cows. Eight multiparous Holstein dairy cows (body weight = 620 ± 15 kg, 60 ± 10 d in milk, mean ± standard deviation) were randomly assigned to treatments in a replicated 4 × 4 Latin square design with a 2 × 2 factorial arrangement of treatments. Each 21-d period consisted of a 14-d diet adaptation period and 7-d collection period. Dairy cows were fed 1 of the following 4 diets: (1) no additional SC without SF supplementation (NSC-SF), (2) no additional SC with SF supplementation (NSC+SF), (3) SC without SF supplementation (SC-SF), and (4) SC with SF supplementation (SC+SF). The diets contained the same amount of forages (corn silage and alfalfa hay). Four isonitrogenous and isoenergetic diets were formulated by replacing corn grain with SC and SF and balanced using change in proportions of canola meal and sugar beet pulp. No interaction was detected between SC and SF supplementation with respect to dry matter intake, milk yield, and composition. A tendency was found for an interaction between inclusion of SC and SF on energy-corrected milk with the highest amount in the SC-SF diet. Ruminal pH and the molar proportion of acetate were affected by SC inclusion, with an increase related to the SC-SF diet. Diets containing SF decreased the concentrations of short-chain fatty acids (4:0 to 10:0) and medium-chain fatty acids (12:0 to 16:0) in milk fat. The addition of SC tended to decrease the concentration of total trans-18:1. These data provide evidence that exchanging SC for corn at 4% of dietary dry matter influenced milk fat content and rumen pH, resulting in a tendency for decreased concentration of trans-18:1 in milk fat. Sucrose alone did not alter the milk fatty acid profile when cows were fed a combination of unsaturated fat and sugar, although several significant interactions between sugar and unsaturated fat were observed. [ABSTRACT FROM AUTHOR]

The objective of this study was to determine whether addition of water to starter would improve performance, rumen fermentation parameters, blood metabolites, and behavior in dairy calves. For this purpose, 30 Holstein male calves (3 d of age; 42.0 ± 4.2 kg of body weight) were randomly assigned to 1 of the following 3 starter diets differing in moisture content: (1) 90% dry matter (DM), (2) 75% DM, and (3) 50% DM. Weaning and final body weight values were found to increase linearly with increasing dietary water. Moreover, starter intake increased linearly during the preweaning and overall periods. Average daily gain also increased linearly in calves receiving the 75% and 50% DM diets compared with those receiving the 90% DM diet. However, treatments had no effects on gain-to-feed ratio. Adding water to a starter with 50% DM led to linear increases in both total volatile fatty acids and molar proportions of acetate and propionate in the rumen but it had no effect on the molar proportions of butyrate, isovalerate, or valerate, nor did it have any effect on acetate-to-propionate ratio. Similarly, times spent on eating, ruminating, standing, lying, and nonnutritive oral behavior exhibited no differences across treatments. Finally, addition of water to the starter diet led to no significant changes in the concentrations of selected blood metabolites, respiration rate, or rectal temperature. Results indicate that calves readily accept wetter feeds with a DM content of 50% and that adding water to starter diets improves calf performance during the hot months of summer. [ABSTRACT FROM AUTHOR]

The objective of this study was to compare the efficacy of the step-up/step-down (SUSD) and step-down (STP) methods of milk feeding on the performance, growth parameters, blood metabolites, and health of dairy calves. For this purpose, 45 Holstein male calves (3 d of age and 41 ± 3 kg of body weight) were randomly assigned to one of the following milk feeding groups: (1) conventional (CONV; 4 L/d milk from d 1 to 52, and 2 L/d milk from d 53 to 56 of the study), (2) STP (6 L/d milk from d 1 to 29, and 4 L/d milk from d 30 to 45 of the study followed by feeding 2 L/d milk from d 46 to 56 of the study), and (3) SUSD (6 L/d milk from d 1 to 5, 8 L/d milk from d 6 to 15, 10 L/d milk from d 16 to 35, 8 L/d milk from d 36 to 42, 6 L/d milk from d 43 to 47, 4 L/d milk from d 48 to 52 of the study followed by feeding 2 L/d milk from d 53 to 56 of the study). Calves were weaned on d 56 and followed until d 70 of the study period. Animals had ad libitum access to the same starter ration during the entire study period (d 3 to 70). Starter intake, total dry matter intake, and average daily gain were greater in the SUSD calves than those in the CONV and STP treatments during the preweaning period. The SUSD procedure was found to increase body weight during the entire study and improved body length, wither height, heart girth, hip height, and hip width on d 56 and 70 of the study compared with the STP and CONV calves. The SUSD treatment increased blood glucose concentration on d 35 compared with CONV and STP procedures. The STP group had a higher starter intake than the CONV and SUSD animals. The STP animals exhibited a higher plasma concentration of total protein and BHBA than did the SUSD animals during the preweaning period. Neither the SUSD nor the STP procedure negatively affected the fecal score. In conclusion, the SUSD milk feeding procedure was found to improve the performance of dairy calves compared with the STP and CONV procedures. However, it appears that the STP procedure induces earlier reticulo-rumen developement in dairy calves than does the SUSD procedure. [ABSTRACT FROM AUTHOR]

This study evaluated the effects of particle size (PS) and dietary level of alfalfa hay (AH) on rumen fermentation parameters, blood metabolites, eating behavior, and growth performance in dairy calves during transition from liquid to solid feed. Sixty newborn dairy calves (41 ± 2.5, kg of body weight) were used in a 2 x 2 factorial arrangement with the factors dietary AH level (medium, 12.5%, or high, 25%, on DM basis) and PS (fine = 1 mm or medium = 3 mm, as geometric means) of AH. Hence, the dietary treatments were (1) medium level of AH with fine PS (M-FPS), (2) medium level of AH with medium PS (M-MPS), (3) high level of AH with fine PS (H-FPS), and (4) high level of AH with medium PS (H-MPS). Particle size of AH did not affect total DMI (TDMI) during the preweaning period, although TDMI was greater for calves fed MPS than in those fed FPS during the postweaning and overall periods. Calves fed MPS spent more time eating solid feed and ruminating and less time on nonnutritive oral behaviors compared with FPS calves. The dietary level of AH did not affect behavioral parameters. Average daily gain of calves was not affected by dietary treatment before weaning. During the postweaning and overall periods, average daily gain was greater in calves fed MPS than in those fed FPS at the 25% AH level, but this effect was absent with 12.5% AH. Furthermore, the rumen pH values on d 35 and 70 of the study were greater for MPS than for FPS, regardless of the dietary level of AH. Effects of AH level, PS, and their interaction did not affect blood glucose concentrations in developing calves. These results indicate that feed intake, feeding behavior, rumen fermentation parameters, and blood β-hydroxybutyrate concentration may be affected by rations differing in forage PS; thus, providing calves with MPS can improve calf performance and reduce their nonnutritive oral behaviors. [ABSTRACT FROM AUTHOR]

The objective of this study was to determine the effects of 2 levels of dietary fat (low and high) offered during the prepartal and postpartal periods on dry matter intake (DMI), plasma concentration of metabolites, and milk yield and composition. Twenty-four Holstein dry cows were assigned on d 21 relative to expected parturition date to 1 of 4 treatments in a 2 x 2 factorial arrangement of 2 levels of fat fed during the prepartal period and 2 levels of fat fed during the postpartal period: prepartal low fat and postpartal low fat (LF-LF), prepartal low fat and postpartal high fat (LF-HF), prepartal high fat and postpartal low fat (HF-LF), or prepartal high fat and postpartal high fat (HF-HF). Prepartal and postpartal LF diets contained no fat supplement. Prepartal HF diets contained 1.60% calcium salts of soybean oil. The proportion of calcium salts of soybean oil was increased to 1.70% of DM for the first 21 d of lactation and to 2.27% of DM from d 21 to 56 of lactation in the HF diet. Diets were fed for ad libitum intake from d 21 before calving until d 56 of gestation. Prepartal DMI was lower for cows fed the HF diet compared with those fed the LF diet (12.6 vs. 16.2 kg/d). Postpartum, cows fed the HF-HF and HF-LF diets had, respectively, the lowest and highest DMI, although no significant differences existed between HF-LF and LF-LF. Net energy intake was higher for cows fed the postpartal HF diets compared with those fed the LF diets. Prepartal fat level had no effect on net energy intake. Cows offered the prepartal HF diet had higher milk yield when offered the postpartal LF diet compared with those offered the postpartal HF diet and no effect of the postpartal fat level was detected when cows were fed the prepartal LF diet. Milk composition was similar among treatments. Plasma cholesterol concentration postpartum was higher for cows fed the prepartal LF diet than for those fed the prepartal HF diet (5.16 vs. 3.74 mmol/L) and postpartal fat level had no effect. Prepartal diet had no significant effect on postpartal plasma triglyceride concentration but the postpartal HF diet increased triglyceride and low-density lipoprotein concentrations compared with the postpartal LF diet. In conclusion, switching from a high to a low fat proportion in the postpartal diet may alleviate the negative effects of a high proportion of fat in the prepartal diet as shown by increased feed intake and milk production during the first 56 d of lactation. [ABSTRACT FROM AUTHOR]

Corn grain with a high phosphorus (P) content (mainly in the form of phytate-P) may need to be processed to improve the digestibility of nutrients for young calves. Processing corn grains can improve the accessibility of phytate-P to the rumen enzymes and increase the bioavailability of P, which benefits the growth and development of calves. The objective of this study was to investigate the effects of feeding starter diets with steam-flaked corn (SFC) compared with ground corn (GC) with 2 P contents of 0.4% and 0.7% DM basis on intake, growth performance, nutrient digestibility, blood metabolites and urinary purine derivatives (PD) in dairy calves. A total of 48 female Holstein dairy calves (3 d old; average initial weight 39.7 ± 3.9 kg) were randomly assigned to a 2 × 2 factorial arrangement of treatments (12 calves/treatment) in a randomized complete block design. The treatment groups were: (1) a starter diet of GC with 0.4% P (GC-0.4P); (2) a starter diet of GC with 0.7% P (GC-0.7P); (3) a starter diet of SFC with 0.4% P (SFC-0.4P); (4) a starter diet of SFC with 0.7% P (SFC-0.7P). Calves received 6 L/d of transition milk on d 2 to 3 and 5 L/d of whole milk on d 4 to 30, which was increased to 7 L/d on d 31 to 45, then decreased to 5 L/d on d 46 to 60 and reduced to a single feeding of 2 L on d 61 to 62. All calves had free access to starter feed and water. All calves were weaned on d 63 and remained in the study until d 83. Rumen fluid samples were collected on d 38 (preweaning) and d 76 (postweaning). Blood samples were collected on d 40 and 80 and urine samples were collected on 4 consecutive days from d 79 to 82 to analyze urinary excretion of PD. The phytate-P content ranged from 0.23 to 0.17 for GC and SFC, respectively. In particular, the interaction between corn processing method and P content showed that the SFC-0.7P diets had a greater intake of starter feed during the pre- and postweaning periods compared with the other experimental groups. In addition, calves fed the SFC-0.7P diet had greater ADG, BW, withers height at weaning, better OM digestibility, higher blood BHB levels, and higher microbial protein synthesis compared with all other groups. Feeding the SFC diet also resulted in improved feed efficiency, improved P digestibility, and a tendency toward a lower rumen pH, albeit with a tendency toward an increase in blood glucose concentration during the preweaning period. In addition, the inclusion of 0.7% P to the starter diet resulted in increased fiber digestibility and a slight improvement in growth performance, which was particularly evident in hip height. Overall, the inclusion of SFC in the calf starter diet, especially in combination with a 0.7% DM basis P supplement, improved growth performance and nutrient utilization in dairy calves compared with GC., (The Authors. Published by Elsevier Inc. on behalf of the American Dairy Science Association®. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).)

Vegetable fat blends are commonly used as fat sources in milk replacers (MR) for calves, but their composition differs considerably from that of bovine milk fat. The aim of this study was to investigate the serum lipid profile of preweaning calves fed twice-daily MR containing 30% fat (% DM). Upon arrival, 30 male Holstein-Friesian calves (BW = 45.6 ± 4.0 kg, age = 2.29 ± 0.8 d) were randomly assigned to 2 experimental diets (n = 15 per treatment): one MR was derived from either vegetable fats (VG; 65% rapeseed and 35% coconut fats) or animal fats (AN; 65% packers lard and 35% dairy cream). The 2 MR formulas contained 30% fat, 24% CP, and 36% lactose. Calves were housed indoors in individual pens with ad libitum access to chopped straw and water. Daily milk allowances were 6.0 L from d 1 to 5, 7.0 L from d 6 to 9, and 8.0 L from d 10 to 35, divided into 2 equal meals and prepared at 13.5% solids. An untargeted liquid chromatography-quadrupole time-of-flight mass spectrometry (LC-QTOF-MS) method was employed to analyze the lipid profiles in the serum of calves sampled from the jugular vein at 35 d of age. In total, 594 lipids were characterized, comprising 25 different lipid classes. Principal component analysis (PCA) showed significant separation between VG and AN, indicating different lipid profiles in the serum. An orthogonal partial least squares discriminant analysis (OPLS-DA) classification model was used to further validate the distinction between the 2 treatment groups. The model exhibited a robust class separation and high predictive accuracy. Using a volcano plot (fold change threshold ≥1.5 and false discovery rate ≤0.05), it was observed that calves fed AN had higher levels of 39 lipid species in serum than calves fed VG, whereas 171 lipid species were lower in the AN group. Lipid classes, such as phosphatidylcholine (PC), phosphatidylethanolamine (PE), sphingomyelin (SM), triglycerides (TG), lysophosphatidylcholine (LPC), and lysophosphatidylethanolamine (LPE), were different. In particular, PC and PE were observed at lower levels in calves fed AN, possibly indicating shifts in cell membrane characteristics, intracellular signaling, and liver functions. In addition, a decrease in certain triglyceride (TG) species was observed in calves fed AN, including a decrease in TG species such as TG 36:0 and TG 38:0, possibly related to variations in the content of certain fatty acids within the AN MR, such as C10:0, C12:0, C14:0, and C18:0, compared with the VG MR. Calves fed AN had lower levels of LPC and LPE, and lysophosphatidylinositol, SM, and phosphatidylinositol species than calves fed VG, suggesting shifts in lipoprotein and lipid metabolic pathways. In conclusion, these results deepen the understanding of how lipid sources in MR can modulate the serum lipidome profiles of dairy calves., (The Authors. Published by Elsevier Inc. on behalf of the American Dairy Science Association®. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).)