Periparturient events in ovariectomized embryo transfer recipient mares.
Ovariectomized mares treated with progesterone have established and maintained pregnancy after embryo transfer. This study evaluated the ability of ovariectomized embryo transfer recipients to successfully undergo parturition, raise a foal, and return to a useful reproductive status. Periparturient events in three ovariectomized embryo transfer recipient mares and three intact mares were compared. All mares foaled normally. Mammary scores were similar for both groups and all mares produced sufficient colostrum and milk to allow normal growth of healthy foals. Plasma progesterone levels decreased to < 5 ng/ml by Day 4 post partum in both groups. Progesterone concentrations continued to decrease and remained at <1 ng/ml in ovariectomized mares, but increased after the first postpartum ovulation (Day 9 to 15) in intact mares. Endometrial involution as determined by histological evaluation was complete in ovariectomized mares by Day 10 post partum and in intact mares by Day 11 post partum. As assessed by palpation per rectum and clearance of bacteria from the uterus, uterine involution was similar in all mares. The three ovariectomized mares subsequently received embryos by transcervical transfer and two of them established pregnancy. These results indicate that normal parturition, lactation, maternal behavior and uterine involution are independent of ovarian function.
Sertich
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PL
Hofmann Center for Reproductive Studies, New Bolton Center University of Pennsylvania, School of Veterinary Medicine Kennett Square, PA 19348 USA.
Hinrichs
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K
Schiereck
D E
DE
Kenney
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RM