Administration of a single dose of 300 IU of human chorionic gonadotropin seven days after the onset of estrus improves pregnancy rate in dairy goats by an unknown mechanism

• Published in: Domestic animal endocrinology Vol. 74; p. 106579
• Main Authors: Côrtes, L.R., Souza-Fabjan, J.M.G., Dias, D.S., Martins, B.B., Maia, A.L.R.S., Veiga, M.O., Arashiro, E.K.N., Brandão, F.Z., Oliveira, M.E.F., Bartlewski, P.M., Fonseca, J.F.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.01.2021
• Subjects: Animals; Chorionic Gonadotropin - administration & dosage; Conception rate; Drug Administration Schedule; Female; Goat; Goats - physiology; hCG; Ovary; Ovulation Induction - methods; Ovulation Induction - veterinary; Pregnancy; Pregnancy Rate; Progesterone; Reproductive Control Agents - administration & dosage; Ultrasonography; Conception rate; Ovary; Goat; Progesterone; hCG; Ultrasonography
• ISSN: 0739-7240; 1879-0054
• DOI: 10.1016/j.domaniend.2020.106579

This study examined the effects of exogenous hCG administration on ovarian function and pregnancy rates in estrous-induced dairy goats during the transition into the breeding season. Eighty-six Toggenburg does received 60 mg of medroxyprogesterone acetate intravaginal sponge for 6 d plus 200 IU of equine chorionic gonadotropin and 30 μg of d-cloprostenol i.m. 24 h before sponge removal, and were then bred for 96 h. Seven days (D7) after first mating the does received either 1 mL of saline (the control group, n = 43) or 300 IU of hCG (the hCG-treated group, n = 43) i.m. Transrectal ovarian ultrasonography (B-mode and color Doppler) was performed on D7, D13, D17, and D21 and ultrasonographic pregnancy detection on D30. Pregnancy rate was higher (P < 0.05) in hCG-treated goats (90.7%; 39/43) than that in control animals (74.4%; 32/43). Accessory luteal structures (ALSs) were detected in 46.5% (20/43) of hCG-treated does. All hCG-treated does that had ALSs and 82.6% of goats without ALS post-treatment remained pregnant. The total luteal area increased (P < 0.05) from D7 to D13 in pregnant animals of both groups, whereas mean vascular area declined (P < 0.05) by D21 in all nonpregnant does. Serum progesterone concentrations increased (P < 0.05) on D21 in pregnant goats of both groups, but they were related to changes in luteal tissue content only in control does throughout the present study. Mean daily numbers of small- and medium-sized antral follicles decreased (P < 0.05) only in pregnant animals of both groups with a decline in medium follicle numbers occurring earlier in hCG-treated (D13) compared with control does (D17). To summarize, a single dose of hCG given on D7 after estrus was followed by a decrease in the number of medium-sized antral follicles in gestating hCG-treated does, induced the formation of ALSs in ~47% of all hCG-treated does, and significantly increased the pregnancy rate in estrous-induced Toggenburg goats in the transition to the breeding season. •A single dose of hCG (300 IU) 7 d after estrus increased pregnancy rates in goats.•Accessory luteal structures formed in only 46.5% of hCG-treated goats.•Luteal vascularity did not change between days 7 and 21 in pregnant goats.•hCG treatment resulted in a transient increase in maximum follicle diameter.•Different putative mechanisms of hCG effects in goats are discussed.