PSIII-5 Evaluation of Gnrh Administration day in the 7 & 7 Synch Protocol for Fixed-Timed Artificial Insemination in Multiparous Beef Cows

Abstract The objective was to determine the effects of a decreased interval progesterone on ovulatory follicle prior fixed-timed artificial insemination (FTAI) in 7 & Synch estrous synchronization protocol using estrus expression (EE), FTAI pregnancy rates (AIPR) 37±2d, and overall (OPR) after 60d bull exposure 90±2d determined via ultrasound. Using conventional Angus semen, multiparous Angus-cross cows (n=201) from two locations were randomized by age days post-partum into treatments. Both treatments used controlled internal drug releasing device (Eazi-breedTM CIDR; 1.38g progesterone) inserted intravaginally –14d simultaneous administration prostaglandin F2α (PGF; 500µg cloprostenol sodium; Estrumate®). In first treatment (7&7), gonadotropin-releasing hormone (GnRH; 86µg gonadorelin; Fertagyl®) administered –7d. second (8&6), GnRH –6d. then PGF CIDR removal 0d, 66±2h GnRH. EE at time an EstrotectTM patch (Rockway Inc., Spring Valley, WI). signified as with 50% or more color rubbed off missing. Subsequently, less than off, not. AIPR, OPR analyzed GLIMMIX procedure SAS 9.4 (SAS Institute Cary, NC.). There significant effect (P=0.01), tendency PR (P=0.08), no (P=0.53) treatment. EE, for 7&7 95±2.1%, 82±3.7% 96.7±1.7% 8&6 86±4.0%, 91±3.1% 98±1.5%, respectively. conclusion, altered timeframe affected tended affect beef cows, suggesting that may improve when 6d, instead 7d, removal.