Effect of hCG and prostaglandin on ovarian, luteal development, and hormonal changes in embryo donor mares during the hot summer months in subtropics.

Background: Commercial embryo flushing of horses has required hormonal management of both the donor and recipient mares throughout the breeding season.

Aim: This study aimed to find out the effect of using human chorionic gonadotropin (hCG) and prostaglandin F2α (PG) on the ovarian and uterine dynamics and hemodynamics, estradiol (E2), progesterone, oxidants-antioxidants, and blood biochemicals in embryo donor mares during the hottest months of the year in a subtropical climate.

Methods: Three Control estrous cycles of native mares (10-20 years; = 10) followed by two treated cycles with hCG and PGF2α were examined daily from May to August using Doppler ultrasound with blood sampling. Circulating, progesterone (P4), total cholesterol, total proteins, albumin, haptoglobin, nitric oxide (NO), catalase, alkaline phosphatase, lactate dehydrogenase (LDH), and myeloperoxidase were measured in blood serum.

Results: Days during the control estrous cycle impacted the dominant follicle (DF) diameter ( < 0.0001), antrum diameter ( < 0.0001), area ( < 0.0001), antral area ( < 0.0001), and color area % ( > 0.05), and corpus luteum (CL) diameter ( < 0.0001). PG tended to impact DF diameter ( > 0.05) but influenced its antrum diameter ( < 0.05), color area ( < 0.05), CL diameter ( < 0.01), and area ( = 0.013). Days after hCG tended to impact DF antrum diameter ( > 0.05) and the antrum area ( > 0.05), but influenced CL diameter ( < 0.0001). PGF2α and hCG increased uterine horn area ( = 0.016) and color area ( = 0.023), total cholesterol ( < 0.0001), and NO ( < 0.0001) levels but hCG increased the levels of myeloperoxidase ( < 0.005), total proteins ( < 0.001), and albumin ( < 0.0001). Globulins achieved the highest level ( = 0.054) but the Albumin/globulin ratio reached a minimum value on Day 0 of the control mares ( < 0.0001). PGF2α increased LDH ( < 0.0001) and sharply declined ( = 0.028) progesterone.

Conclusion: In conclusion, the treatment protocols of hCG and PGF2α showed minimal effects on the produced ovulating follicles and can be used during the summer season to manage embryo donor mares.