EFFECT OF PROSTAGLANDIN-F2-ALPHA ADMINISTERED BEFORE ESTRUS SYNCHRONIZATION WITH NORGESTOMET AND ESTRADIOL VALERATE ON CALVING RATES OF BEEF-COWS

Three experiments were conducted to evaluate the effects of prostaglan din F-2 alpha treatments 5, 9, and 14 d before Syncro-Mate B(R) on cal ving rates of 1,072 beef cows from inseminations at a pre-set-time. Th e administration of prostaglandin F-2 alpha 5 d before Syncro-Mate B d ecreased (P < .01) calving rates. This reduction was associated with l ower (P < .05) calving rates in cows administered Syncro-Mate B in the first half of the estrous cycle. Calving rates were unaffected in cow s administered prostaglandin F-2 alpha 9 d before Syncro-Mate B. The a dministration of prostaglandin F-2 alpha 14 d before Syncro-Mate B red uced (P < .05) calving rates in previously anestrous cows. In summary, prostaglandin F-2 alpha should not be administered to postpartum cows 5 to 14 d before Syncro-Mate B synchronization.