Effects of Early Weaning and Exogenous Hormone Treatment on Bovine Postpartum Reproduction

Abstract

SEVENTY-NINE lactating cows were assigned to one of four treatment groups: (1) early weaning of calves (30 days postpartum), (2) early weaning and hormone therapy, (3) suckling calves throughout the experiment and (4) suckling calves and hormone therapy. The hormone therapy was initiated at 30 days post-calving and consisted of a progestogen implant combined with injections of FSH-P and an injection of estradiol-17β. The cows were with fertile bulls for 70 days (30 to 100 days postpartum). The hormone treatment increased (P<.05) the proportion of cows exhibiting estrus and reduced the interval from parturition to first estrus (P<.05). Early weaning also decreased the interval to first estrus (P<.01). An interaction (P<.10) was detected between the effects of weaning and hormone therapy on the first service conception rate and the interval from calving to conception. Hormone therapy reduced the conception rate to first service of early-weaned cows and lengthened the interval to conception. However, in the suckled cows, the hormone treatment increased the conception rate to first service and shortened the interval to conception. Copyright © 1972. American Society of Animal Science . Copyright 1972 by American Society of Animal Science.