Vol. 10, Special Issue 10 (2021)

Author(s):
Rajkumar R, Palanisamy M, Prabaharan V, Raja S and Sathesh Kumar S

Abstract:
The objective of the present study was to assess the effect of Cosynch protocol on pre-ovulatory follicle size and first service conception rate in repeat breeding crossbred cows. A total of forty repeat breeding crossbred cows were randomly divided into two group containing 20 cows in each group. In Group I (n=20) cows, GnRH (Receptal, 10 μg) was administered intramuscularly on day 0; PGF_2α (Pragma, 500 μg) was administered intramuscularly on day 7 and second GnRH was administered 48 hours post PGF_2α injection. Cows were inseminated at the time of second injection of GnRH. Cows in group II (n=20) served as a control and were inseminated at observed estrus without any hormonal intervention. Transrectal ultrasonography was carried out at the time of insemination to determine the pre-ovulatory follicle size. The mean diameter of pre-ovulatory follicle size was 11.44±0.21 mm in cosynch group and 11.20±0.21 mm in control group and the difference was not statistically significant (p>0.05). There was no significant association between the pre-ovulatory follicle diameter and conception both in cosynch treatment group and control group. The first service conception rate was 60.00 per cent in cosynch group as compared to 30.00 per cent in control group. Thus, fertility in repeat breeding cows can be enhanced by controlled breeding using cosynch method of synchronization.