Effects of flunixin meglumine on pregnancy establishment in beef cattle

The objective of this research was to determine effects of a single injection of the PG synthesis inhibitor flunixin meglumine (FM; 1.1 mg/kg of BW, intramuscularly) approximately 13 d (range 10 to 15 d) after AI on pregnancy establishment. Three experiments were conducted using estrus-synchronized heifers and cows. Technicians and AI sires were equally represented across treatments within locations and experiments. Bulls were introduced on the day of FM treatment. Pregnancy to AI was diagnosed 28 to 50 d after AI using ultrasonography. In Exp. 1, beef heifers (n = 1,221) were divided within 5 locations to receive FM or no further treatment (control). At insemination, heifers were divided into 2 similar pastures or pens, and approximately 13 d later, 1 group of heifers within each location was processed through an animal handling facility to administer FM treatment. There was no location x treatment interaction (P = 0.62) on AI pregnancy rates, so data were pooled. Pregnancy rates to AI were reduced (P = 0.02) among heifers receiving the FM treatment procedure (66%) compared with control heifers (72%). In Exp. 2, suckled beef cows (n = 719) were assigned within 2 locations to receive FM or no further treatment (control) approximately 13 d after AI. At insemination, control and FM cows were divided into separate pastures, and only FM cows were handled after AI for the FM treatment procedure. There was no location x treatment interaction (P = 0.75), so data were pooled. Pregnancy rates to AI did not differ (P = 0.80) between FM (57%) and control cows (59%). In Exp 3, beef heifers (n = 247) and suckled beef cows (n = 335) from 1 location received no injection (control) or injection of FM approximately 13 d after AI when all cows and heifers were processed through a working facility. Pregnancy rates to AI were not different (P = 0.37) between FM (45%) and control (42%) cows or between FM (56%) and control (55%) heifers. We conclude FM administration at 1.1 mg/kg of BW approximately 13 d after AI did not improve pregnancy establishment in beef cows and heifers and that the effects of handling heifers at this time may decrease pregnancy establishment.