2003 Volume 56 Issue 5 Pages 316-319
The present study was carried out to determine the efficacy of replacing the second GnRH with hCG (GnRHPGF2αhCG) in Ovsynch used for timed AI in cows. In the firstexperiment, Holstein cows were divided into 3 groups according to post-estrus day: day 5-6, day 10-11, and day 15-16 (n = 5 for each group). In each group, ovulation was highly synchronized in cows treated with GnRH-PGF2α-hCG (hCG: 3, 000 IU). In thesecond experiment, Holstein cows were randomly divided into 2 groups and each cow was treated with either GnRHPGF2α-hCG (n=42) or Ovsynch (n=41). Conception rates were 52.4% for cows treated with GnRH-PGF2α-hCG and 51.2% for cows treated with Ovsynch. It was estimated that replacisng GnRH with hCG for ovulation synchronization saved \703 per cow and Y1, 533 per conception. These results show that ovulation synchronization and timed AI for dairy cows can be performed without conception-rate reduction and at lower costs by replacing the second GnRH with hCG in Ovsynch.
