The aim of this study was to investigate the preventive efficacy of intramuscular injection of Gonadotropin Releasing Hormone (GnRH) at the 15^th day of postpartum period on cystic and inactive ovarium problem and the effects of this injection on fertility on cows with retained placenta (RP).

A total of 60 cows (RP:36 and Control:24), in various breed, aged 2.5-10 years old, were used as material of this study. The animals whose oestrus was detected after the 45^th postpartum day were inseminated naturally or artificially and pregnancy diagnosis were ultrasonographically performed following 35 days of insemination.

The animals with RP (n:36) were randomly divided into two equal subgroups, of which one subgroup (n:18) received 0.021 mg i.m. Busereline acetate (5ml) and the other (n:18) 5 ml physiological saline at day 15 postpartum. Three times in a week (15 times in total ) 10 ml blood samples from 10 randomly selected animals of each group were collected from jugular vein using 10 ml sterile vacuumed tubes between 15-50 days at postpartum period. Meanwhile, the animals without RP were also divided into two equal subgroups of which one subgroup obtained 0.021 mg i.m. Busereline acetate (5ml) and the other group 5 ml physiological saline at day 15 postpartum. Three times in a week (15 times in total) 10 ml blood samples from 5 randomly selected animals of each group were collected from jugular vein into 10 ml sterile vacuumed tubes between 15-50 days postpartum period. The progesteron levels of the collected blood samples were determined by enzyme immune assay (EIA).

Fertility parameters including interval of calving to first oestrus, calving to first service, calving to conception, and services per conception, pregnancy rate in first service and total pregnancy rate were determined.

It was determined that the intervals between calving to first oestrus and also calving to first service prolonged in RP cows received 0.021 mg Busereline acetate at day 15 postpartum. No effects of GnRH administration on other fertility parameters were observed. The effect of GnRH administration on the fertility parameters of the cows without RP was determined to be non-significant. Howewer, GnRH injections in animals without RP shortened significantly calving to first oestrus and calving to first service interval when compared to animals with RP. GnRH administration was observed to be ineffective in the incidence of cystic and inactive ovarium in animals with or without RP.