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

Abstract

Forty 63-day-old Holstein male calves previously raised on a limited whole milk-dry calf starter regime were fed an intake of a vit A depletion ration to gave an anticipated 10-lb. increase in body weight/7-day period until the blood plasma level of vit. A for each calf decreased to 10.0 [mu]g. % or less. At this time, when their average age was 88 t 8 days and average weight was 223 [plus or minus] 32 lb., each calf was fed in addition to the depletion ration 1 of 5 levels of carotene, 12, 18, 24, 30, and 36 [mu]g- from alfalfa or 1 of 5 levels of vit. A, 2, 4, 6, 8, and 10 [mu]g. from a dry carrier/lb. of body weight/day for 16 consecutive 7-day periods. Upon completion of this period, during which the average weight increase/calf was 213 [plus or minus] 22 lb., the calves were slaughtered. Regressions of plasma and liver concentrations of carotenoids and of vit. A and of the logarithm of spinal fluid pressure on the logarithm of carotene and of vit. A intakes were derived and found to be linear. From these relationships it was found that to maintain a plasma vit A value of 10 [mu]g. %, a daily intake of 31 [mu]g. of carotene or a daily intake of 3.8 [mu]g. of vit. A/lb. of body weight was required. To achieve a liver concentration of 0.6 [mu]g./g., a daily carotene intake of 30 [mu]g. or a daily vit. A intake of 3.0 [mu]g./lb. of body weight was necessary, and to maintain a minimum spinal fluid pressure of 120 mm. of water a daily intake of 33 [mu]g. of carotene or 6.4 [mu]g. of vit. A/lb. of body weight was needed. In addition to these, carotene and vit. A intakes in [mu]g./lb. of body weight/day re-quired to prevent papillary edema were greater than 36 and 8, respectively; to prevent squamous metaplasia in the main duct of the parotid gland required 24 and 6.0, respectively; and to prevent similar lesions in the interlobular ducts of the same gland required 30 and 4.0, respectively.