Relative Value of Carotene from Alfalfa and Vitamin A from a Dry Carrier Fed at Medium to High Levels to Holstein Calves

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Abstract
Forty-eight 63-day-oid Holstein male calves, previously fed limited whole milk to 35 days of age and up to 3.0 lb. of starter and ad libitum chopped alfalfa hay, were fed an intake of a vitamin A depletion ratio to give an anticipated 10 lb. increase in live weight per 7-day period. When blood plasma vitamin A level for each calf decreased to 10.0 gamma/100 ml or less, each calf was fed in addition to the depletion ration one of 3 levels of carotene, 60, 180, and 540 gamma from alfalfa, or one of 3 levels of vitamin A, 5.5, 10.8, and 21.0 gamma from a dry carrier, daily per pound of live weight for 12 successive 7-day-age periods. Upon completion of the supplement feeding period half of the calves were slaughtered. The remaining calves were then maintained on only the depletion ration until the blood plasma vitamin A level decreased to less than 4 gamma/100 ml for 2 consecutive 7-day-periods to observe vitamin A depletion time. The following results were obtained: 1. Plasma carotenoids and vitamin A concentrations increased at diminishing rates with an increase in the carotene intake from artifically dehydrated alfalfa. Liver carotenoids and vitamin A concentrations as well as vitamin A depletion time increased proportionally with increased carotene intake. 2. When calves received vitamin A intake from a dry carrier, inappreciable differences were observed for plasma and liver carotenoid concentrations. Plasma vitamin A increased at diminishing rates and liver vitamin A and vitamin A depletion time at constant rates with increased vitamin A intake. 3. From the relationships of plasma and liver vitamin A concentrations and vitamin A depletion time with carotene or vitamin A intake, it was found that on a weight basis carotene fed at the 60 gamma intake level was equivalent to about l/5th to l/7th as much as vitamin A (alcohol); at the 180 gamma intake level, 1/10th to 1/13th; and at the 540 gamma intake level, l/20th to l/24th.