A 15 year old hunter-under-saddle Thoroughbred Mare presented to Cornell University’s Theriogenology Service for a two year history of an inability to maintain pregnancy. The mare had previously delivered seven foals successfully, but had begun having a variety of reproductive issues starting in 2009. These issues included endometritis, a rectal tear, and delayed embryological development.
Upon presentation in May of 2012, the mare was bright, alert and responsive with all vital signs within normal limits and was of good body condition (5/9). A breeding soundness exam revealed the following: she was creating and ovulating normal follicles; her hormones were at appropriate levels; her endometrium had a biopsy score of 2A (suggesting a 50-70% chance of carrying any foal conceived to term); her uterine culture and cytology were clear; no abnormalities to her reproductive tract were seen or palpated other than a permanent Caslick’s in place due to poor perineal conformation.5
To further evaluate the problem, the mare was bred to a known, fertile stallion and did not conceive. The mare was then bred to a known, fertile stallion and an embryo flush was performed with no embryo obtained. These steps helped determine that it was not a stallion issue. Based on the breeding soundness exam and the stallion findings, it was deduced that the mare’s infertility was most likely due to a uterine tubal motility or blockage issue that was preventing the zygote from traveling down the tube and settling in the uterus. In an attempt to obtain a foal from this mare, it was decided that she should undergo oocyte transfer and that her daughter would be used as the oocyte recipient. The mare was sedated and placed in stocks. To obtain the oocytes, a transvaginal ultrasound-guided approach was used and only pre-ovulatory follicles were targeted. A double-lumen aspiration needle was used to allow lavage of the follicle – maximizing the likelihood of obtaining an oocyte. The recovered fluid was examined under microscope but no oocytes were obtained. The lateness of the breeding season prevented further investigation at this point. Mares with tubal infertility are candidates for a procedure known as laparoscopic prostaglandin E2 (PGE2) application. In this procedure, a sterile embryo transfer pipette is used during a laparoscopic procedure to place a gel form of PGE2 on the dorsal surface of the uterine tube. This allows the smooth musculature of the uterine tube to relax and increases transport through the tube. The theory is to allow debris that has accumulated in the uterine tube to clear into the uterus. While uncontrolled, a preliminary study performed in 2005 suggested that this technique could have up to a 93% success rate of conception of a pregnancy up to two years post application. The mare in this study underwent this procedure in January of 2013.