Reproductive and metabolic characteristics of dairy cattle supplemented with beta-carotene.

Seventy-eight Holstein cows alternately were assigned at calving to receive beta-carotene supplementation or act as controls to determine effects of beta-carotene on reproduction and carotene, luteinizing hormone, progesterone, insulin, glucose, and glucagon concentrations in blood plasma. Cows were fed a corn silage-based complete ration. Biweekly jugular blood samples were collected beginning the week after parturition through 90 days. At day 30, supplemented cows received 600 mg synthetic beta-carotene daily for 60 days. Plasma carotene reached a peak of 2.45 micrograms/ml compared to 1.50 micrograms/ml in controls. Supplementation significantly increased plasma carotene but had no effect on luteinizing hormone, progesterone, insulin, glucose, glucagon, or reproductive measures. Days to first heat, days to first breeding, days open, and services per conception averaged 74, 74, 95, and 1.7 for supplemented cows and 64, 76, 102, and 1.9 for control cows. Progesterone increased as lactation progressed. Somatic cells were not different between supplemented and control cows. Supplementation of beta-carotene did not improve reproductive efficiency or alter luteinizing hormone, progesterone, insulin, glucose, or glucagon in blood plasma or affect somatic cells in milk.