Gonadotropin-Releasing Hormone and Conception of Holsteins

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Abstract
Effects of gonadotropin-releasing hormone (100 .mu.g) and time of artificial insemination on fertility were examined in lactating dairy cows at 1st, 2nd and 3rd services. Inseminations were either soon after detected estrus (0 h) or 12 h later, and cows were given gonadotropin releasing hormone or saline after inseminations. Conception at 1st service was not improved by hormone treatment, but conception rates at repeat services were improved by nearly 21% when cows were treated with gonadotropin-releasing hormone within 30 s after insemination. Inseminations soon after detection of estrus (0 h) followed by hormone treatment resulted in the highest conception rates for all services. Time of the insemination (0 vs. 12 h) had no effect on conception. Administering gonadotropin-releasing hormone at repeat services should improve conception rate of lactating dairy cows.