Effect of eCG dose on ovarian hemodynamics, hormonal profiles, and prolificacy rate when estrus was induced during low-breeding season in Beetal goats.

Objectives of the experiment were to determine the effect of two doses of equine chorionic gonadotropin (eCG) in a standard synchronization protocol based on a short-term progesterone (P4 ) priming on ovarian structures and hemodynamics, concentrations of steroid hormones, and prolificacy rate when estrus was induced during low-breeding season (LBS) in Beetal dairy goats. We hypothesized that inclusion of eCG in a short-term P4 priming-based synchronization protocol would increase the blood perfusion to ovarian structures leading to enhance estrus and ovulatory responses and prolificacy rate in goats. Forty-two multiparous acyclic goats were blocked by body condition and, within block, assigned randomly to receive saline as control (CON), low eCG (L-eCG; 300 IU), or high eCG (H-eCG; 600 IU) dose. Initially, a controlled internal drug release (CIDR) device was placed in the anterior vagina on d -8, followed by removal of CIDR on d -3, concurrent with the administration of PGF2α and eCG according to their respective treatments. Goats were monitored for estrus response. B-mode and Doppler ultrasonography were performed with 12 h interval, starting from d -3 until natural breeding (d 0), and then on d 5, 10, 15, and 20 post-breeding to monitor follicular and luteal dynamics and blood flow, respectively. Blood was sampled at 0, 12, 24, 36, and 60 h after CIDR removal to quantify plasma concentrations of estradiol-17β (E2 ), whereas plasma concentrations of P4 were assayed at d 5, 10, 15, and 20 after breeding. Pregnancy and prolificacy rates were determined at d 30 and 150 after breeding, respectively. Data were analyzed with mixed-effects models, and orthogonal contrasts were used to evaluate the effect of treatment [Con vs. (½ L-eCG + ½ H-eCG)] and dose of eCG (L-eCG vs. H-eCG). Data are presented in sequence as CON, L-eCG, H-eCG (LSM ± SEM). The estrus intensity score (152.9 vs. 182.7 vs. 186.5 ± 15.1; P = 0.02) was greater in eCG-treated goats as compared to CON. Administration of eCG reduced the intervals to standing estrus (66.2 vs. 41.8 vs. 48.9 h ± 5.5; P = 0.05), breeding (70.2 vs. 44.4 vs. 45.4 h ± 4.5; P = 0.03) and ovulation (84.5 vs. 61.2 vs. 63.4 h ± 6.2; P = 0.05) compared to CON goats. The mean growth rate of pre-ovulatory follicle was greater (1.11 vs. 1.49 vs. 1.45 mm ± 0.08; P = 0.01) in eCG-treated goats resulting in an increased diameter of pre-ovulatory follicle (6.27 vs. 7.20 vs. 7.31 mm ± 0.07; P < 0.01) and corpora lutea (6.75 vs. 8.26 vs. 8.07 mm ± 0.42; P = 0.04) than CON. The mean follicular blood flow did not differ among treatments; however, the mean luteal blood flow was greater in L-eCG-treated goats (0.81 vs. 1.61 vs. 1.07 cm2 ± 0.12). The mean concentrations of E2 (4.03 vs. 5.21 vs. 4.78 pg/mL ± 0.42; P = 0.04) and P4 (4.85 vs. 6.39 vs. 6.22 ng/mL ± 0.34; P = 0.04) were greater in eCG-treated goats. The twinning rate did not differ between treatments; nevertheless, prolificacy rate was greater (P = 0.04) in L-eCG-treated goats. Collectively, our data suggest that administration of eCG improves the induction of estrus and ovarian dynamics. Administration of L-eCG enhances prolificacy rate, therefore, a low dose of eCG might be practically beneficial to improve reproduction during LBS in acyclic Beetal dairy goats.