Submitted to: Workshop Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 6/7/2004
Publication Date: 7/1/2004
Citation: Larson, J.E., Lamb, G.C., Stevenson, J.S., Marston, T.W., Johnson, S.K., Day, M.L., Geary, T.W., Kesler, D.J., Dejarnette, J.M., Schrick, F.N. 2004. Estrus synchronization of suckled beef cows by using gnrh, prostaglandin f2¿ (pgf), and progesterone (cidr): a multi-location study.. Workshop Proceedings. Cattlemen's Day 2004. pg. 7-10. Interpretive Summary: Estrus was synchronized in 2,630 suckled beef cows from 14 locations with one of five treatments using CIDRs, GnRH, and PGF with breeding by estrus and/or timed AI (TAI) only. The protocols used are described in the technical abstract. The addition of a GnRH injection at CIDR insertion increased pregnancy rates of cows. The CO-Synch protocol with only TAI resulted in the poorest pregnancy rates, and pregnancy rates greater than 50% at 9 of 14 locations. Addition of TAI with GnRH following an 84 h period of breeding by estrus increased pregnancy rates, and use of a TAI protocol alone would yield greater pregnancy rates than protocols involving only a short period of estrus detection with AI. The protocol that most consistently yielded the greatest pregnancy rates was the Hybrid Synch + CIDR protocol, with pregnancy rates greater than 50% at 10 of 14 locations.
Technical Abstract: We determined whether a fixed-time AI (TAI) protocol could yield similar pregnancy rates to a protocol requiring detection of estrus and if adding a CIDR to GnRH + PG-based protocols would enhance fertility. Estrus in 2,630 suckled beef cows from 14 locations was synchronized and artificial insemination occurred after five treatments: 1) a CIDR for 7 d with 25 mg of PG at CIDR removal, followed by detection of estrus and AI for 84 h with any cow not detected in estrus by 84 h receiving 100 'g of GnRH and TAI at 84 h (Control; n = 511); 2) GnRH, followed in 7 d with PG, followed in 60 h by a second injection of GnRH and TAI (CO-Synch; n = 551); 3) CO-Synch plus a CIDR during the 7 d between the first injection of GnRH and PG (CO-Synch+CIDR; n = 547); 4) GnRH, followed in 7 d with PG, followed by detection of estrus and AI for 84 h, with any cow not detected in estrus by 84 h receiving GnRH and TAI at 84 h (Hybrid Synch; n = 513); and, 5) Hybrid Synch plus a CIDR during the 7 d between the first injection of GnRH and PG (Hybrid Synch+CIDR; n = 508). Pregnancy was diagnosed by transrectal ultrasonography and blood samples were collected (d '17 and '7, relative to PG) to determine cycling status. The percentage of cows cycling at the initiation of estrus synchronization was 67%. Pregnancy rates among locations ranged from 39% to 67%. Pregnancy rates were greatest for the Hybrid Synch+CIDR (57.9%) treatment, although not different from the CO-Synch+CIDR (53.6%) and Hybrid Synch (53.0%) treatments, but greater (P < 0.05) than the Control (52.3%) and CO-Synch (43.4%) treatments. Controls did not differ from CO-Synch+CIDR or Hybrid Synch. Overall, the Hybrid Synch+CIDR protocol consistently achieved the greatest pregnancy rates; however, CO-Synch+CIDR was a reliable TAI protocol that gives producers the option to eliminate detection of estrus when inseminating beef cows.