Effect of Preinsemination Injection of Gonadotropin-Releasing Hormone on Reproductive Performance of Dairy Cattle

Abstract

Holstein-Friesian cows and heifers on 2 farms were injected with 100 μg GnRH or saline as soon as possible after detection of oestrus. Time from detection of oestrus to injection was 2.2 h, and from injection to breeding 6.4 h. The CR of 282 animals injected with GnRH was 51.8% vs. 51.5 for 264 animals injected with saline. The CR did not differ between the 2 groups at 1st, 2nd, 3rd or later services, nor at the following oestrus. There were no significant differences between groups in the interval to next oestrus or in the service period.