Submitted to: Journal of Reproduction and Fertility
Publication Type: Abstract only
Publication Acceptance Date: 4/1/2000
Publication Date: 8/1/2000
Citation: GEARY, T.W., WHITTIER, J.C., LEFEVER, D.G., NISWENDER, G.D., NETT, T.M., HALLFORD, D.M. EVALUATION OF THE GNRH/PGF*2ALPHA PROTOCOLS FOR SYNCHRONIZATION OF OESTRUS/OVULATION IN BEEF COWS. JOURNAL OF REPRODUCTION AND FERTILITY. 2000. v. 54. p. 515. Interpretive Summary:
Technical Abstract: Beef cows (n=1939) were used to evaluate variations of the Ovsynch protocol for synchronization of estrus/ovulation. Treatment groups included direct comparisons of the Ovsynch protocol (n=220) vs Syncro- Mate B (n=216), Ovsynch protocol (n=627) vs the CO-Synch protocol (n=594), and Select Synch (n=116) vs 2x PGF (n=109). The Ovsynch, CO- Synch and Select Synch protocols include the following injection schedules: GnRH - 7 d PGF - 2 d GnRH - 1 d - AI; GnRH - 7 d PGF - 2 d - GnRH + AI; and GnRH - 7 d PGF + 5 d and AI 12 h after detection of estrus, respectively. Calf removal (48 h) initiated at the time of PGF was evaluated in a subset of cows receiving the Ovsynch (n=235) or CO- Synch (n=234) protocol. Daily ultrasound and HeatWatch were used to evaluate estrous and ovarian response to the Select Synch protocol (n=57). Progesterone analysis indicated that each of the GnRH/PGF protocols was capable of inducing ovulation/estrus in previously anestrous cows. Pregnancy rates were greater (P<0.025) for Ovsynch (54%) treated cows than Syncro-Mate B (42%) treated cows. Pregnancy rates were not different (P>0.1) among Ovsynch (58%) or CO-Synch (54%) treated cows. However, 48 h calf removal improved (P<0.05) pregnancy rates by 8%. Synchronization, conception and pregnancy rates were not different among Select Synch (77, 61 & 47%, resp.) or 2x PGF (81, 60, & 49%, resp.) treated cows. Ovarian response of cows that were between d 15 and 17 of their estrous cycles at the first GnRH injection was poor and these cows exhibited estrus 11 +/- 19 h before the PGF. The GnRH/PGF protocols can result in high pregnancy rates to timed inseminations or breeding by estrus in beef cows.