Effect of a CIDR insert and flunixin meglumine, administered at the time of embryo transfer, on pregnancy rate and resynchronization of estrus in beef cattle

The objectives of this study were to evaluate the effects of flunixin meglumine (FM), an inhibitor of PGF2α synthesis, and insertion of an intravaginal progesterone-releasing device (CIDR), on pregnancy rates in beef cattle embryo transfer (ET) recipients, and to examine the effect of a CIDR after embryo transfer on the synchrony of the return to estrus in non-pregnant recipients. Cows (n = 622) and heifers (n = 90) at three locations were assigned randomly to one of four groups in a 2 × 2 factorial arrangement of treatments with FM administration (500 mg i.m.) 2-12 min prior to ET, and insertion of a CIDR (1.38 g progesterone) immediately following ET as main effects. Fresh or frozen embryos (Stage = 4 or 5; Grade = 1 or 2) were transferred on Days 6-9 of the estrous cycle and CIDR devices were removed 13 days after ET. Recipients at Location 2 only were observed for signs of return to estrus. Recipients that returned to estrus at Location 2 were either bred by AI or received an embryo 7 days after estrus. Following the initial ET, there was an FM × location interaction on pregnancy rate (P < 0.01; Location 1, 89% versus 57%; Location 2, 69% versus 64%; Location 3, 64% versus 67% for FM versus no FM, respectively). Pregnancy rates of embryo recipients were not affected by CIDR administration (P > 0.05; 65% with CIDR, 70% without CIDR), however, the timing of the return to estrus was more synchronous (P < 0.01) for recipients given a CIDR. Pregnancy rate of recipients bred following a return to estrus did not differ between cows receiving or not receiving a CIDR for resynchronization (P > 0.13). Effects of FM on pregnancy rate were location dependent and CIDR insertion at ET improved synchrony of the return to estrus.