Reproductive Performance of Lactating Holstein Cows Fed Supplemental β-Carotene

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Abstract
Fifty-six Holstein cows were used in a replicated study to determine whether supplemental .beta.-carotene improved reproductive performance. Each of two replicates was of completely randomized design with 2 .times. 2 factoral agreement of two diets with or without .beta.-carotene supplementation. On a dry matter basis, diet 1 was 5% hay, 20% haylage, 25% corn silage, and 50% concentrate. Diet 2 was 7.5% hay, 42.5% corn silage, and 50% concentrate. The diets contained adequate amount of vitamins A, D, and E. From 10 d postpartum until pregnancy was confirmed by rectal palpation, half the cows on each diet received a supplement of 400 mg .beta.-carotene per head daily. The remaining cows on each diet received a supplement of 160,000 IU vitamin A per head daily. Supplemental .beta.-carotene increased plasma .beta.-carotene throughout the trials. Median days to first ovulation, first service, days open, and mean services per conception were: 22, 77, 97, and 1.6 for cows receiving .beta.-carotene supplement compared with 19.5, 73, 82, and 1.9 in controls. Supplementation did not affect first service conception rate, uterine involution, or milk yield. Incidence of follicular cysts, luteal cysts, pyometra, and endometritis in cows fed .beta.-carotene were 11, 7, 0, and 7% compared with 8, 21, 4, and 13% in control cows. Supplemental .beta.-carotene did not improve the fertility of Holstein cows.