Impact of buserelin acetate or hCG administration on day 5 post-ovulation on subsequent luteal profile and conception rate in Murrah buffalo (Bubalus bubalis)

The present study aimed to establish the impact of buserelin acetate or hCG administration on day 5 post-ovulation on subsequent luteal profile and conception rate in buffalo. The buffalo (n = 45) were subjected to an estrous synchronization protocol (synthetic analog of PGF2α administered, through intramuscular route, 11 days apart), followed by artificial insemination (AI) during mid to late estrus. On day 5 post-ovulation, buffalo were administered (i.m.) normal saline (Control, n = 14), buserelin acetate (20 μg, d5-BA, n = 14) or human chorionic gonadotropin (3000 IU, d5-hCG, n = 17). Ovarian ultrasonography was conducted on the day of induced estrus and on days 0, 5, 12, 16 and 21 post-ovulation to assess preovulatory follicle or corpus luteum (CL) diameter. Also, on these days, jugular vein blood sampling was conducted for the estimation of plasma progesterone. First service conception rate was greater (χ2 = 5.18, P > 0.05) in d5-BA and d5-hCG groups (71.4% and 47.1%, respectively) as compared to control (28.6%). Both treatment groups had a greater (P < 0.05) CL diameter and plasma progesterone during the post-treatment period in comparison to that control treatment group. Treatment-induced accessory CL formation was observed in 92.9% and 76.5% buffalo of d5-BA and d5-hCG groups, respectively. In conclusion, buserelin acetate and hCG administration on day 5 post-ovulation leads to accessory CL formation that may have a role in enhancing conception rate.