Equine chorionic gonadotropin (eCG) improves follicular dynamics, estrus expression, ovulation and pregnancy rate in CIDR based estrus synchronization protocol in Nili-Ravi buffalo
Reproduction of buffalo is hampered due to poor ovarian reserves, vague estrus signs, anestrus, prolonged postpartum and calving intervals and decreased fertility. Synchronization of estrus and ovulation including CIDR based protocols are well established in cows and gaining popularity in buffaloes. However, these need modifications based on physiology of estrous cycle in buffaloes. The present study tested the hypothesis that if the addition of eCG to a CIDR based synchronization protocol improves ovarian follicular dynamics, estrus behavior, ovulation and pregnancy rate in Nili-Ravi buffalo. Lactating multiparous Nili-Ravi buffaloes (n=88) received CIDR (1.38 g progesterone Pfizer Co, USA) device for 7 days and prostaglandin F2α (Dalmazine, cloprostenol, Fatro, Italy) on day 6.These, buffaloes were randomly assigned to receive either saline (without eCG, n=45) or equine chorionic gonadotropin 1000 IU (Chronogest PMSG, Intervet, Holland) i.m. (eCG, n=43) concurrent with prostaglandin F2α treatment of the CIDR protocol (Day 6). Fixed time, two inseminations were performed at 48 and 60 hours after CIDR removal (Day 7). Pregnancy was diagnosed 35-40 days post AI using transrectal ultrasonography. The mean size of dominant follicle just before ovulation did not differ in eCG treated buffaloes compared to without eCG (14.8 ± 0.3 vs.14.5 ± 0.5; P > 0.05). Mean growth rate of the ovulatory follicle was higher in the eCG group compared to without eCG (1.8 mm ± 0.0 vs.1.4 mm ± 0.1; P < 0.05). Mean interval from CIDR removal to ovulation was shorter in eCG treated buffaloes compared to without eCG (70.9 ± 2.0 h vs. 77.5 ± 2.3 h; P < 0.05).The estrus response and intensity was greater in the eCG group than the group without eCG (100% vs. 91%; P < 0.05), (3.2 ± 0.1vs 2.4 ± 0.1; P < 0.05), respectively. Similarly, ovulation and pregnancy rates were higher in the eCG group than those without eCG (82.9 % [34/41] vs. 69.4% [26/37]; P > 0.05), (53.4% [23/43] vs. 24.4% [11/45]; P < 0.05) respectively. Therefore, we conclude that addition of eCG before P4 device removal improves ovulatory follicle growth rate,estrus behavior, and pregnancy rate in FTAI program in buffalo. These data has strong implication in hastening buffalo reproduction.
Keywords: eCG, fertility, buffalo