Improving fertility in multiparous cows by inducing ovulation with GnRH agonist - gonadorelin or human chorinic gonadotrophin

Abstract

This study was designed to assess the effects of the GnRH agonist gonadorelin and human chorionic gonadotrophin administered at first artificial insemination on the fertility of lactating dairy cows. The lactating dairy cows were divided into three groups: the hCG-group consisting of primiparous and multiparous cows that expressed the specific behavior of estrus with AI 12 hours after the end of estrus along with administration of 1500 IU of human chorionic gonadotropin (hCG); the GnRH-group consisting of primiparous and multiparous cows that showed the specific behavior of estrus with AI 12 hours after the end of estrus along with administration of 2 mL of Gonadorelin; and the control group (C-group) consisting of primiparous and multiparous cows that showed the behavior specific to estrus and that were artificially inseminated (AI) 12 hours after the end of estrus signs without any treatment. According to our results, administering GnRH agonist or hCG products to multiparous cows in order to induce ovulation increases the pregnancy rate during the first artificial insemination (46.6%, 57.1% vs. 22.2%, P ≤ 0.05). Both products don't have any effects on primiparous dairy cows (45%, 42.9% vs. 50%, P > 0.05).