Timed-insemination of beef heifers using Cosynch with or without MGA



Journal Title

Journal ISSN

Volume Title


Kansas State University. Agricultural Experiment Station and Cooperative Extension Service


Our purpose was to determine if feeding melengesterol acetate (MGA) for 1 week in combination with gonadotropin-releasing hormone (GnRH) and prostaglandin-F2" (PGF) would better synchronize heifers for timed artificial insemination. Sixty-nine yearling beef heifers received an injection of GnRH 7 days before receiving an injection of PGF. Half of the heifers were fed MGA between the GnRH and PGF injections (Cosynch+MGA), whereas the remaining heifers were not (Cosynch). All heifers were given a second GnRH injection 2 days after PGF and inseminated at that time. Pregnancy rate for the Cosynch group (43%) was greater (P<0.05) than that for the Cosynch+MGA group (15%). This experiment suggests that short-term feeding (7 days) of MGA in concert with a Cosynch protocol was detrimental to fertility in beef heifers.



Beef, Heifers, AI, Synchronization, MGA, GnRh, PGF2a