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Postpartum Reproductive Function of Dairy Cows as Influenced by Energy and Phosphorus Status¹

Michigan State University, East Lansing 48824

Abstract

To determine if energy or phosphorus status would affect postpartum reproductive performance, we assigned primiparous heifers, six per group, to either high (135% NRC) or low (85% NRC) energy, and high (138% NRC) or low (98% NRC) phosphorus in a 2 x 2 factorial design. Treatments were continued from parturition through 84 days postpartum, after which standard diets were fed. The entire experiment was repeated. Reproductive function was almost identical among energy and phosphorus groups. However, no cow with peak serum progesterone below 2.7 ng/ml before insemination conceived to that insemination. Interval from parturition to first observation of serum progesterone (3 ng/ml) was correlated with serum phosphorus (r = -.34), glucose (r = -.33) and growth hormone (r = .51). In addition, body weight change, milk production and glycemia did not seem to affect reproduction markedly. These data suggest that neither energy nor phosphorus status, within the ranges studied, influences reproduction of dairy cows.

¹ Published with approval of the Director of the Agr. Exp. Sta. as Journal Article No. 8925.

² Dept. of Dairy Sci., Univ. of Wisconsin, Madison 53706.

³ Dept. of Large Anim. Surg, and Med.

⁴ Dept. of Dairy Sci.