EFFECT OF OVSYNCH AND PRESYNCH PROTOCOLS ON FERTILITY AND SERUM PROGESTERONE IN REPEAT BREEDER COWS UNDER FIELD CONDITIONS

Abstract

Repeat breeder cows, maintained under field conditions, were inseminated at observed estrus without any treatment (control, n=15), were subjected to Ovsynch (n=13; d0 and d9 - GnRH 10 μg im; d7 - PGF2α 500 μg im; day 10 - AI 16 h after d9 GnRH) or Presynch (n=16; Two PGF2α at 14-day interval and initiating Ovsynch 12 day after the second PGF2α) protocols. The pregnancy rate on d45 post-AI for control, Ovsynch and Presynch groups were 20%, 46.1% and 37.5%, respectively. In both treatment groups, serum progesterone between pregnant (P) and non-pregnant (NP) cows at the time of first GnRH injection was similar (p>0.05). Serum progesterone on the day of AI was lower (p<0.05->0.05) and on d6 post-AI was higher (p<0.05) in P cows compared to their NP counterparts in all the groups. In brief, ovsynch protocol even without pre-synchronization enhances conception rate in repeat breeder cows.