It is a challenge to keep a sufficient vitamin E level (2 mg/l) in calf plasma after weaning, and this seems to be critical for a good immune response. Two experiments were performed in order to find the most efficient source and dose of vitamin E in calf starter concentrates to keep plasma vitamin E level above the critical level after weaning. Experiment 1 (Exp 1) and 2 (Exp 2) included a total of 32 and 40 calves, respectively, from at least 2 weeks before weaning until
at least 2 weeks after weaning. In Exp 1, calves were infused through mouth a daily dose of 200 mg of different vitamin E sources including no α-tocopherol in the feed (0 dose; Control), and 200 mg/d of either RRR-α-tocopherol
(ALC), RRR-α-tocopheryl acetate (ACT) or all-rac-α-tocopheryl acetate (RAC). In Exp 2, a dose response study was carried out with 0, 60, 120, and 200 mg/kg of ALC in pelleted calf concentrates. In both Exp 1 and 2, calves had free access to concentrate, grass hay, and fresh water. In Exp 1 and 2, body weight and average daily gain were not affected by either different sources or doses of α-tocopherol, respectively. In Exp 1, plasma RRR-α-tocopherol level was affected by source of α-tocopherol (P<0.001), week (P<0.001) and interaction between them (P<0.001). At weaning, plasma RRR-α-tocopherol was 4.3, 3.3, 1.5, and 1.0 μg/ml in ALC, ACT, SYN, and control, respectively. In Exp 2, total plasma α-tocopherol level was affected by dose of ALC (P=0.04), week (P<0.001), and tendency for interaction between dose and week (P=0.06). At weaning, 36, 31, 28% reduction in plasma α-tocopherol level was observed compared to beginning of experiment in 0, 60, and 120 mg/kg of ALC, respectively; however, in 200 mg/kg of ALC, more than 9% increase in plasma α-tocopherol level was observed. In addition, 200 mg/kg of ALC was able to keep plasma α-tocopherol high after weaning (3.1 and 2.9 μg/ml in weeks 1 and 2 after weaning, respectively), which is well above the recommended level. In conclusion, the ALC was the most efficient source of α-tocopherol supplementation to be used in a calf starter concentrate. In addition, the 200 mg/kg of ALC in calf starter concentrate was the only effective dose to keep the plasma vitamin E levels higher than the critical level after weaning.
