Effect of Calcium and Energy Status During the Postpartum Period on Reproductive Performance in Dairy Cows

Abstract

Pregnancy rate, a function of heat detection and conception rate, determines the number of days postpartum at which cows become pregnant from the voluntary waiting period.67 Cows expressing one or more estruses during the first 30 days postpartum had improved pregnancy rates compared with anestrous cows.83 This observation indicates that the physiological and hormonal events associated with estrus help restore uterine and ovarian function to a state conducive to pregnancy. A number of studies have demonstrated the relationship between hypocalcemia and parturient disorders such as dystocia, retained fetal membranes (RFM), and ketosis.13,30,68 These disorders predispose the cow to metritis, which can affect the energy status of the cow. This influences ovarian activity and resumption of cyclicity during the postpartum period. The energy status of the lactating dairy cow has differential effects on early follicular development and competence, ovulation and subsequent corpus luteum (CL) function during the postpartum period. As our understanding of the endocrinology and reproductive physiology of the postpartum cow has advanced, it is clear that reproductive and nutritional management systems need to be integrated to achieve optimal reproductive efficiency. Objectives of this presentation are 1) to describe the association between calcium status and periparturient disorders 2) to relate the differences in ovarian activity to energy status in postpartum dairy cows 3) to examine the effects of protein and fat on reproductive function during the postpartum period, and 4) to document the beneficial effects of bovine somatotropin (bST) on first-service pregnancy rates when integrated into a reproductive management program for timed insemination.