Effect of supplemental vitamin A on the performance of beef cows and their calves.

Abstract

The role of vitamin A in the nutrition of the beef cow and neonatal calf has received only limited attention. In early work, Guilbert and Hart (1935) found that rations deficient in carotene caused impaired reproductive performance in beef cows. Later, Baker, Pope and MacVicar (1954) found that supplementation of carotene to cows during lactation was essential for normal vitamin A nutrition of the calves regardless of whether the cows had low or high liver vitamin A stores at parturition. Church, Pope and Mac-Vicar (1956) found that liver vitamin A depletion occurred in lactating beef cows although the carotene intakes were above the N.R.C. (1964) recommended levels. Physical symptoms of vitamin A deficiency have been reported in fattening steers fed high grain rations which had been previously considered adequate in carotene content (Perry et al., 1957; Mitchell et al., 1960). Liver vitamin A stores were severely depleted in steers fed high corn silage rations containing carotene in excess of the presumed requirement (Jordan et al., 1963; Smith et al., 1964).