Uterine involution in mares treated with progesterone and estradiol-17 beta

Bacteriology, histology, and scanning electron microscopy were used to evaluate uterine involution in 27 mares treated with daily injections of 150 mg of progesterone and 10 mg of estradiol-17 beta, commencing within 18 hours of parturition. These findings were compared with those for 24 untreated mares at postpartum day 10 or 11. The treatment resulted in significantly (P less than 0.05) greater uterine gland proliferation. Gland density was significantly (P less than 0.05) greater in mares treated for 6 to 10 days than in those treated 2 to 5 days. The proportion of ciliated cells to secretory cells lining the endometrial surface was significantly (P less than 0.05) greater in mares during delayed foal estrus than in those at postpartum days 10 to 11. The proportion of ciliated to secretory cells increased with increasing duration of treatment. It was concluded that treatment with progesterone and estradiol-17 beta allowed additional time for uterine involution in the early postpartum period.