Carotene in the Ration of Dairy Cattle. I. The Influence of Long Periods of Suboptimal Carotene Intake on the Carotene and Vitamin A Values of the Blood, Liver, and Milk Fat of Dairy Cows

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Abstract
Data are presented showing carotene and vitamin A values for blood plasma, liver, and milk fat of cows fed suboptimal carotene rations prenatally and over periods up to 5 years after birth compared with normally fed animals. Liver biopsies show extremely low carotene and vitamin A values for dairy cattle fed 50, 90 and 130 [mu]g of carotene/kg body weight. Repeated injections every 5 days of either 250,000 or 1,250,000 I.U. of vitamin ester failed to result in any appreciable increase of liver vitamin A or carotene in cows on a suboptimal carotene ration. The possibility of liver storage of vitamin A being limited by previous nutrition is indicated.