Vol. 10, Issue 12, Part F (2025)

Author(s): Guruvandana P, Abdul Azeez CP, Promod K and Leeba Chacko

Abstract: The objectives of the present study were to assess the effect of administration of human chorionic gonadotropin (hCG) instead of second GnRH in the Ovsynch ovulation protocol on the fertility of repeat breeding cows. Twenty-four repeat breeder (RB) cows free of any detectable anatomical abnormalities and subclinical endometritis were selected and randomly divided into three groups, each with eight animals, group I (Ovsynch), group II (modified Ovsynch) and group III (Control). Group I and group II RB cows received Ovsynch protocol and modified Ovsynch protocol respectively, initiated on day 5 of oestrous cycle, in which group II animals received hCG instead of second GnRH, followed by timed artificial insemination 18 h after second GnRH or hCG injection. Group III animals were inseminated on the day of standing oestrus. Blood samples were collected from RB cows for serum oestrogen and serum progesterone estimation. Ultrasonographic examination of uterus and ovaries were done to assess endometrial thickness, number and type of follicles and diameter of corpus luteum. All RB cows in treatment groups responded to protocols. There was no significant difference in the duration and time taken for onset of oestrus. The serum progesterone concentration in group II day 10 post AI was significantly higher (p<0.05) than group I and III. The overall conception rate in group I, group II and group III were 50, 50 and 25 percent, respectively. It can be concluded modified Ovsynch protocol is effective in the management of repeat breeding in cattle with potential advantage by enhancing corpus luteum development and serum progesterone level.

DOI: 10.22271/veterinary.2025.v10.i12f.2853