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Gonadotropin-Releasing Hormone and Conception of Holsteins^{1, 2, 3,}

Department of Animal Sciences and Industry Kansas State University, Manhattan 66506

ABSTRACT

Effects of gonadotropin-releasing hormone (100 µg) and time of artificial insemination on fertility, were examined in lactating dairy cows at first, second, and third 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 first 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 versus 12 h) had no effect on conception. Administering gonadotropin-releasing hormone at repeat services should improve conception rate of lactating dairy cows.

¹ Contribution No. 83-123-J, Kansas Agricultural Experiment Station, Manhattan, KS 66506.

² This research was part of regional research project NC-113, "Methods for Improvement of Fertility in Cows Postpartum."

³ Gonadotropin-releasing hormone (Cystorelin®) and partial financial support were kindly donated by M. D. Brown of CEVA Laboratories, Inc., Overland Park, KS 66212.