Relationship between hepatic and butterfat vitamin A concentrations in beef cattle receiving negligible carotene

Abstract

Hereford heifers with a mean stage of gestation of 171 days were transferred from pasture to yards and fed restricted all-grain rations for 24 weeks. The sorghum grain used contained negligible carotene. Liver vitamin A analyses on biopsy samples were done initially and at the beginning of the twenty-fourth week. Butterfat analyses were carried out at the completion of the all-grain feeding period when the mean stage of lactation of the heifers was 70 days.
Mean initial liver vitamin A levels of 300 μg/g (500-149 μg/g) declined to 150 μg/g (354-54 μg/g).
The vitamin A potency of the butterfat averaged 24·2 I.U./g (10·2-39·4 I.U./g), The butterfat did not contain detectable carotenoids. The concentration of vitamin A in butterfat declined as yield increased.
Vitamin A in butterfat was significantly correlated with vitamin A in liver (r = + 0 · 71).
Final levels of liver vitamin A were significantly correlated with initial levels (r = + 0·80).
In this method of feeding, adequate initial reserves of vitamin A are necessary in the dams to ensure the immediate vitamin A requirement of the suckling calf.