Effects of gonadotrophin releasing hormone on reproductive performance of dairy cows with retained placenta.

The effects of gonadotrophin releasing hormone (GnRH) on the reproductive performance of dairy cows with retained placenta were studied. Three hundred and seventy-eight cows diagnosed as having retained placenta received intramuscular injections of either 2 mL sterile water or 200 micrograms of GnRH in 2 mL sterile water between day 8 and day 14 postpartum. Rectal palpation was performed at the time of treatment and ten to 20 days after treatment in order to determine the rate of uterine involution. Thereafter, monthly rectal examinations were carried out until insemination. Pregnancy diagnosis was made by rectal palpation at 40 days or more after breeding. Using the entire experimental population, there were no significant differences between GnRH-treated and control cows for the rate of uterine involution, the occurrence of reproductive problems, the interval from parturition to first observed estrus, the interval from parturition to first insemination, the interval from parturition to conception, the number of services per conception, the total number of services per cow regardless of conception and the incidence of culling for infertility. When the data for herds in which breeding began earlier in the postpartum period (herds having a mean less than or equal to 80 days from parturition to first service for retained placenta cows) were considered, the GnRH treatment resulted in a significantly shorter (p less than or equal to 0.01) calving to conception interval as compared to control cows. Also, there was a significant reduction (p less than or equal to 0.05) in the total number of services per cow regardless of conception and a significant reduction in the interval from parturition to first service.(ABSTRACT TRUNCATED AT 250 WORDS)