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

Abstract

Summary Forty-eight 63-day-old male Holstein 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 ration to give an anticipated 10 lb. increase in live weight per 7-day period. When the blood plasma vitamin A level for each calf decreased to 10.0 γ/100 ml. or less, each calf was fed in addition to the depletion ration one of three levels of carotene, 60, 180, and 540 γ from alfalfa, or one of three levels of vitamin A, 5.5, 10.8, and 21.0 γ from a dry carrier, daily per pound of live weight for 12 successive 7-day age periods. Upon the 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 γ/100 ml. for two consecutive 7-day periods for the purpose of observing 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 artificially dehydrated alfalfa. Liver carotenoids and vitamin A concentrations as well as vitamin A depletion time increased proportionally with increased carotene intake. 2. When the 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 γ intake level was equivalent to approximately 1/5 to 1/7th as much as vitamin A (alcohol); at the 180 γ intake level, 1/10th to 1/13th; and at the 540 γ intake level, 1/20th to 1/24th.