Prepartum Milking. II. The Effect of Prepartum Milking on the Carotene and Vitamin A and Proximate Composition of Colostrum

Abstract

Summary The effect of prepartum milking for 10 days prior to the calculated parturition date on the carotene, vitamin A and proximate composition of colostrum has been studied in 44 cows. In addition, the changes occurring in the carotene and vitamin A contents of both pre-milk and colostrum were observed in 14 of these cows milked for 10 or more days prepartum. Secondarily, the effect of feeding one million USP units of vitamin A daily for 30 days prior to the calculated parturition date was measured. Prepartum milking resulted in significant decreases in the carotene, vitamin A, protein and ash contents and in the specific gravity and significant increases in the lactose content of the colostrum from the first six milkings postpartum. Both carotene and vitamin A decreased with successive milkings in the pre-milk and colostrum of cows milked for more than 10 days prepartum. Parturition affected this decrease by temporarily causing a decrease in the negative trend. The prepartum feeding of supplementary vitamin A increased significantly the vitamin A content of both pre-milk and colostrum and decreased the carotene content of colostrum.