Relationship of Plasma β-Carotene and Vitamin A to Luteal Function in Postpartum Cattle

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Abstract
The influence of plasma concentrations of .beta.-carotene and vitamin A on in vivo progesterone production by bovine corpora lutea after gonadotropin-releasing hormone-induced LH release was assessed in 39 postpartum dairy cows. Thirty Holsteins and nine Jerseys were given 100 .mu.g gonadotropin-releasing hormone on d 12 of an estrous cycle, which began from 30 to 49 d postpartum. Concentrations of .beta.-carotene and vitamin A in plasma and progesterone and LH in serum were determined prior to gonadotropin-releasing hormone injection (0 h); serum progesterone and LH concentrations were also determined 1, 2, and 3 h after injection of gonadotropin-releasing hormone. Serum concentrations of progesterone and LH were increased by gonadotropin-releasing hormone. Incremental progesterone production in an analysis of covariance was influenced by breed as well as the interactions of breed with vitamin A, of season with .beta.-carotene, and of season with vitamin A. The regression coefficients were positive for .beta.-carotene and negative for vitamin A in all cases. In conclusion, luteal function in the postpartum cow appears to be related to plasma concentrations of .beta.-carotene and vitamin A.