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Studies on Ketosis in Dairy Cattle. X. The Effect of a Vitamin A Deficiency¹

Department of Dairy Husbandry, Maryland Agricultural Experiment Station, College Park

ABSTRACT

Detailed observations were made on 13 cows which were maintained on a low carotene diet for approximately 4 mo. prepartum and 3 wk. postpartum. The vitamin A depletion of these cows was accentuated by the feeding of a concentrate ration containing 40 per cent soybeans which was later shown to exert a marked depressing action on blood plasma and liver vitamin A. Five of the cows received a vitamin A supplement prepartum which resulted in the birth of four normal-appearing calves. The other eight cows dropped calves which showed marked signs and/or symptoms of a vitamin A deficiency. The blood plasma vitamin A values of these eight cows were extremely low during the postpartal period and one cow exhibited marked symptoms of a vitamin A deficiency. Of the eight cows, four were maintained on a low level of energy intake for 3 wk. postpartum (50 per cent of requirements). The five cows receiving the vitamin A supplement prepartum were on the same low level of energy intake postpartum. In spite of the severe vitamin A depletion and deficiency produced in these cows, none showed symptoms of ketosis and the degree of hypoglycemia produced by partial fasting was as large in the case of the vitamin A-supplemented cows as in the vitamin A-depleted cows. The cows exhibiting a marked vitamin A depletion but receiving higher levels of energy intake postpartum exhibited normal levels of glucose during the postpartal period. None of the cows showed symptoms of ketosis. It is concluded that not only is spontaneous ketosis, as it is observed under field conditions, not due to a vitamin A deficiency but that a vitamin A deficiency per se does not produce ketosis in dairy cows in the postpartal period.

¹ Paper no. A268, contribution no. 2211 of the Maryland Agricultural Experiment Station.