Effect of Plane of Nutrition of Beef Cows on Depletion of Liver Vitamin A during Gestation and on Carotene Requirements during Lactation

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Abstract
Two experiments were conducted with grade Hereford cows, divided into two groups and maintained at low or adequate levels of nutrition (protein and energy) during the last 5 to 7 months of gestation and the first 12 weeks of lactation to determine the effect of nutritive plane on vitamin A metabolism. During the gestation phase, both groups were fed low carotene rations. At parturition, one-half of each group received 27–30 mg. of carotene per head daily, while the remaining cows received 126–150 mg. The low plane of nutrition, as compared to the adequate level, had no apparent effect on vitamin A depletion during gestation in the first experiment, but did delay depletion in the second experiment. During lactation, the low plane of nutrition resulted in less liver depletion in one of two experiments. Blood levels of carotene and vitamin A in the cows and their calves were not significantly affected. The low plane of feeding had an adverse effect on the nutrition of the calves, resulting in less gain in weight and apparent malnourishment. Carotene supplementation during lactation, as practiced in these experiments, failed to promote vitamin A storage in the liver of the cows irrespective of plane of nutrition. The high level of carotene (126 to 150 mg. per day) decreased rate of liver depletion and increased levels of carotene and vitamin A in the plasma; although neither level was sufficient to prevent symptoms of vitamin A deficiency among the calves. Apparently, for the production of healthy calves, range cows on low carotene rations during the latter half of gestation require a daily carotene intake of 20 mg. or more per 100 lb. during subsequent lactation, regardless of plane of nutrition. Copyright © . .