Reproductive and Metabolic Characteristics of Dairy Cattle Supplemented with β-Carotene

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Abstract
Holstein cows (78) 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 .mu.g/ml compared to 1.50 .mu.g/ml in controls. Supplementation significantly increased plasma carotene but had no effect on luteinizing hormone, progesterone, insulin, glucose, glucagon or reproductive measures. Days to 1st heat, days to 1st 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.