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When supplementing lamb diets with vitamin E, an equivalence factor of 1.36 is used to discriminate between RRR-α-tocopheryl acetate and all-rac-α-tocopheryl acetate. However, more recent studies suggest a need for new equivalence factors for livestock animals. The current study aimed to determine the effect of RRR- and all-rac-α-tocopheryl acetate supplementation on α-tocopherol deposition in lamb tissues. A total of 108 Rasa Aragonesa breed lambs were fed increasing amounts of all-rac-α-tocopheryl acetate (0.25, 0.5, 1.0 and 2.0 g/kg compound feed) or RRR-α-tocopheryl acetate (0.125, 0.25, 0.5 and 1.0 g/kg compound feed) by adding them to a basal diet that contained 0.025 g/kg feed of all-rac-α-tocopheryl acetate as part of the standard vitamin and mineral mixture. The diets were fed for the last 14 days before slaughtering at 25.8±1.67 kg BW. Within 20 min after slaughter samples of muscle, heart, liver, brain and spleen were frozen at −20°C until α-tocopherol analysis. Increased supplementation of either vitamin E sources led to a significant increase (P < 0.001) in α-tocopherol concentration in all tissues studied. The tissue with the highest α-tocopherol concentration was the liver followed by spleen, heart and muscle. At similar supplementation levels (0.25, 0.50 and 1.0 g/kg compound feed), α-tocopherol content in the selected tissues was not affected by α-tocopherol source. However, the ratios between RRR- and all-rac-α-tocopheryl acetate increased with the increasing α-tocopherol supplementation (at 0.25 and 1.0 g/kg compound feed), from 1.06 to 1.16 in muscle, 1.07 to 1.15 in heart, 0.91 to 0.94 in liver and 0.98 to 1.10 in spleen. The highest relative proportion of Ʃ2S (sum of SSS-, SSR-, SRS- and SRR-α-tocopherol)-configured stereoisomers was found in the liver of lambs supplemented with all-rac-α-tocopheryl acetate accounting for up to 35 to 39% of the total α-tocopherol retained, whereas the proportion of Ʃ2S-configured stereoisomers in the other tissues accounted for

The increasing availability of automated milk dispensers on dairy farms facilitates ad libitum milk supply but weaning calves from high milk allowances is challenging. This study evaluated effects of gradual weaning methods on starter intake, growth, selected blood parameters and weaning distress in ad libitum fed dairy calves during weaning and early post-weaning periods. Thirty-six male Holstein (n = 30) or crossbred (n = 6) calves were individually housed from days 2 to 14 of age and had ad libitum access to milk replacer (MR) from teat buckets. From days 15 to 84 of age, calves were grouped and had ad libitum access to MR, starter, straw and water from automated feeders. At day 35, calves were blocked (age and breed), and randomly assigned to a weaning method: (1) linear fixed (LIN), MR supply was stepped down to 6 l/day on day 36, and linearly reduced between days 36 to 63 from 6 to 2 l/day. (2) Step-down (STEP), MR supply was stepped down to 6 l/day from days 36 to 48, 4 l/day from days 49 to 56 and 2 l/day from days 57 to 63. (3) Dynamic (DYN), at day 36, MR supply was reduced for each individual calf to 75% of the average voluntary consumption between day 29 and 35, then maintained for 9 days, reduced to 50% for 10 days, and to 25% for 9 days. The DYN calves received more MR during weaning than LIN calves, whereas STEP calves had intermediate MR intake. Starter intake was not affected by weaning method. The DYN calves (1.33±0.08 kg/day) grew faster and were heavier than STEP calves (1.10±0.08 kg/day) during post-weaning period, whereas no difference was observed between LIN calves (1.23±0.08 kg/day) and others. At days 70 and 84, concentrations of β-hydroxybutyric acid were higher in LIN calves compared to STEP and DYN calves. Hair cortisol concentrations were not affected by weaning method. During the gradual weaning process CP intake seemed to recovered earlier than metabolizable energy (ME) intake in all treatments, suggesting that ME rather than CP could be the first limiting factor for growth during weaning. These results highlight the post-weaning benefits of DYN and LIN weaning methods when compared with more abrupt step-down strategies.

Male Holstein calves commonly receive minimal quantities of milk replacer (MR) to speed up weaning and reduce costs. Studies with Holstein female calves show that early life feed restriction affects energy metabolism later in life. Aiming to test this hypothesis, 120 Holstein bull calves (48.4 ± 2.2 kg of BW and 20 ± 3.2 d of age) housed in 24 pens were blocked and randomized to two treatments: A low calf MR allowance (LP) (two daily doses of 2 l each, 582 g/d of DM), or a high MR allowance (HP) (two daily meals of 4 l each, 1164 g/d of DM). Calves were weaned at day 49 of the study and slaughtered at 32.8 ± 0.5 weeks of age. Throughout the study, animals had ad libitum access to a common compound feed, straw, and water. Twenty-four animals were randomly selected for an intravenous glucose tolerance test (IVGTT). The IVGTT was performed at week 6 and 12 of the study and consisted of an intravenous glucose infusion and sequential blood sampling up to 90 min after glucose infusions. Calves were heavier for HP until week 12, after which the difference disappeared. By design, the MR intake was higher in the HP group resulting in a higher energy intake and a higher average daily gain in the preweaning phase. Blood glucose curves were not different at week 6, but at week 12, 5 min after the infusion, glucose was higher in HP calves. Insulin curves were not different at week 6. Nevertheless, in week 12, a higher insulin concentration was observed for HP 5, 10, 15, 20, 30, 35, and 45 min’ postinfusion, indicating a higher requirement of insulin to control glycemia. Differences between HP and LP calves were also observed for the quantitative insulin sensitivity check index, maximum insulin concentration, and insulin delta at week 12. Blood glucose reached maximum concentration within 5–10 min of the IVGTT test, and the concentration was, on average, 8.58 and 10.80 mmol/l at weeks 6 and 12, respectively. Insulin reached maximum concentration within 10–15 min of the IVGTT, and concentrations were, on average, 33.32 and 32.61 μUI/ml at weeks 6 and 12, respectively. Doubling MR supply improved animal growth up to weaning, but these differences disappeared by the end of the feeding period. Despite similar responses to glucose infusions preweaning, higher milk supply seemed to decrease insulin sensitivity after weaning.

The recent trend in the dairy industry towards elevated planes of milk feeding of young calves requires reconsideration of calf milk replacer (CMR) formulations. The fat:lactose ratio in CMR is typically lower than that of whole milk and effects of increasing fat inclusion at the expense of lactose in CMR on nutrient metabolism and gut function of rearing calves are not sufficiently understood. Therefore, the current study aimed to determine the effect of increasing replacement of lactose by fat on growth performance, nutrient digestibility and metabolism, and glucose/insulin sensitivity. A total of 40 male calves (1.7 ± 0.10 days of age, 46.7 ± 0.76 kg BW) were blocked based on arrival date and randomly assigned to one of four treatments containing differing levels of fat and lactose (18F: 18.8% and 47.6%; 22F: 22.3% and 42.8%; 26F: 26.0% and 38.6%; 30F: 30.1% and 33.8%, fat and lactose DM, respectively). Calves were individually housed for the duration of the 11 week study and received their CMR (150 g/L) twice a day (0700 and 1600 h) from a teat bucket. The CMR feeding schedule consisted of 6 L/d from d 2 to 14, 7 L/d from d 15 to 56, and then 4 L/d during gradual weaning from 56 to 63 days. Pelleted starter, chopped straw, and water were available ad libitum throughout the study. Measurements included feed intake, growth, nutrient digestibility, fecal composition, and blood parameters. A glucose tolerance test (GTT) was performed between 28 and 32 days of age. By design, metabolizable energy intake from CMR increased linearly with fat level, but this did not result in a difference in BW, ADG, or concentrate intake. Fecal composition remained unaffected by treatment except for higher fat content in 22F compared to 26F. Also, plasma non-esterified fatty acids and total bilirubin differences were limited to 22F having the highest values whereas 26F had the lowest values. Regarding the GTT, total area under the curve (AUC) for glucose was highest in 22F and 26F and lowest in 18F whereas the AUC between 30 and 60 min for glucose was highest in 26F and lowest in 18F and 22F. Overall, altering the lactose:fat ratio in CMR did not affect growth performance while having minor effects on nutrient metabolism, but future investigation should focus on physiological consequences and effects in adult life to understand biological impact of fat and lactose levels in CMR for rearing calves.