The Influence of the Ration and Early Rumen Development on the Changes in the Plasma Carotenoids, Vitamin A and Ascorbic Acid of Young Dairy Calves

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Abstract
Preliminary investigations indicated that the development of the rumen in young calves is influenced by the type of ration fed. Expts. were conducted, therefore, to determine the effect of different rations and early rumen development on the levels of vitamin A, carotenoids and ascorbic acid in the blood of young dairy calves. Rumen inoculations, accomplished by direct transfer of cud material from cows in the herd to the calves, were supplied to about half the calves in order to make certain that they had access to the microorganisms present in the rumens of adult animals. Rumen inoculations were effective in preventing the usual drop in blood plasma ascorbic acid between the 7th and 14th days of age when only alfalfa hay and milk were fed,but were ineffective when grain was included in the ration. A ration of whole milk and alfalfa hay alone resulted in carotenoid levels considerably higher after 14 days of age than was observed when grain was included in the ration. Rumen inoculations had no marked effect on the blood carotenoid levels. Neither the inoculations no marked effect on the blood carotenoid levels. Neither the inoculations nor the type of ration fed markedly influenced the blood plasma vitamin A. When grain was introduced into the ration of 64-ciay-old calves, which had been fed only alfalfa hay and milk until that time, a marked reduction in hay consumption and blood carotenoids resulted. Plasma vitamin A increased and ascorbic acid declined during the same period. These results, when correlated with the effect of different rations on the development of various rumen microorganisms in these calves, indicate that palatable, high-quality hay stimulates the early development of rumen function in the young calf and appears to have a favorable physiol. effect in meeting the vitamin needs of these animals.