Effect of GnRH Administration at Different Periods of Estrous Cycle in Cows

The objective of the present study was to ascertain the efficacy of GnRH when administered at different periods of the estrus cycle in cows. One hundred multiparous repeat breeding crossbred cows selected were randomly divided into four uniform groups. Group I was kept as untreated control. Buserelin acetate 20μg i/m (GnRH) to each cow in Group II, III and IV was administered at day 11^th-13^th of the previous cycle, at estrus and at day 11^th-13^th post insemination, respectively. The conception rates in group I, II, III and IV were 12, 12, 52 and 16% respectively. In the present study, Buserelin acetate administered at estrus in group III significantly enhanced the fertility, but failed to effect when administered either at 11^th-13^th of the previous cycle in group II and or at day 11–13 post insemination in group IV.