Effect of GnRH on fertility in crossbred cows

Abstract

The effect of GnRH on pregnancy was studied using 85 cros, bred cows. Buserelin, an analogue of GnRH was administered intramuscularly at the time of standing oestrus in a 10mg dose to 25 (treatment 1), and 20mg dose to 30 (treatment 2) cows. Further 30 cows were administered normal saline solution and used as control. The pregnancy rate to first AI was increased by treatment 2 (40.0%) relative to control (23.3%) and treatment 1 (28.0%). A further 16.7%. (control), 32.0% (treatment 1) and 30.0% (treatment 2) cows were found pregnant following second AI and 6. 7% (control), 8.0% (treatment 1) and 10.0% (treatment 2) got pregnant to the third AI. None of these differences were significant. The cumulative pregnancy rate for all 3 services was lower for control (46.7%) than treatment 1 (68.0%) and treatment 2(80.0%) and difference between control and treatment 2 was significant (P<0.05). There was no difference in service/conception between control (1.64) and treatment 1 cows (1.70) but this improved by treatment 2 (1.50). The results showed that GnRH treatment at the time of oestrus can be used to increase pregnancy rate in cows and the effect is dose dependent.