Surgical correction of rectovaginal fistula in mares and subsequent fertility.

The research investigates fertility rates in mares that have undergone surgical correction of rectovaginal fistula (RVF). It suggests that excellent fertility can be achieved without a need to delay breeding until the following breeding season, and that breeding in the same cycle as the surgery is an effective method for maintaining normal fertility and yearly foaling intervals.

Objective and Methodology

• The study aims to evaluate the fertility of mares after undergoing surgical procedures to address rectovaginal fistula (RVF), an abnormal connection between the rectum and vagina, and assess the impact of the timing of breeding post-surgery.
• The researchers performed surgical repair on 28 mares at varying times in relation to foaling, from 30 days to 24 months, and relative to the time of rebreeding. Some mares were rebred during the same cycle as the surgical procedure, while in other cases breeding was delayed.
• The postoperative fertility of the mares was evaluated to measure the efficiency of the surgery and the impact of the timing of rebreeding.

Findings and Results

• At the time of surgery, two mares were already pregnant. Among the remaining mares, 87% (20 out of 23) conceived from their first service post-surgery, whether this service was right before or right after the surgical procedure.
• When the timing of breeding was considered, the pregnancy rates were high across different intervals: mares bred in the same cycle as the surgery had a 100% success rate (5/5); those bred in the next cycle following surgery had an 83% rate (5/6); and those bred in the following breeding season after surgery had an 83% rate (10/12).
• The foaling rates, or the rate of successful births, was also high and correlated positively with the pregnancy rates: mares bred in the same cycle as the surgery had an 80% rate (4/5), the one’s bred in the cycle following surgery had a 67% rate (4/6), and those bred in the following breeding season had a 58% rate (7/12).
• The two mares that were already pregnant before surgery experienced successful births, proving the safety and effectiveness of the surgery procedure.

Conclusions and Recommendations

• The study effectively demonstrates that high fertility can be achieved following surgical repair of RVF in mares, negating the common practice of delaying breeding until the next breeding season.
• The research also revealed that the method of breeding mares in the same cycle as the surgery can yield impressive fertility rates. This technique represents a previously unexplored strategy for maintaining normal fertility and a consistent yearly foaling interval, and it is recommended to consider this method for future applications.