Some surgical interventions in broodmares—such as emergency cesarean sections—are urgent, life-saving interventions. Others, however, are elective surgeries aimed at improving a mare’s future reproductive abilities.

During Cavalcade Education’s 2022 reproduction symposium, in Hyde Park, New York, Lauren Pasch, DVM, Dipl. ACT, board-certified theriogenologist at Rhinebeck Equine in New York, described common elective reproductive procedures in mares and why veterinarians might perform them.

When the goal is to correct subfertility rather than save a life, Pasch stressed the importance of taking the time to have a thorough discussion with your veterinarian before pursuing the procedure. “Find out if she is a good surgical candidate and if there are other factors affecting her fertility besides surgically correctable anatomical defects,” she said. “Subfertility is often multifactorial. Some advanced cases of endometritis (inflammation of the endometrium, or uterine lining) and fibrosis (scarring) have irreversible degenerative changes in the uterine lining that even surgery can’t fix, so have your veterinarian start with an endometrial biopsy to have a better idea of what you’re working with.”

If you’ve decided to go the surgical route, have an honest discussion with the surgeon about the expected longevity of the procedure’s results. Make sure you’re aware of any maintenance the mare might need down the road. For instance, a surgically repaired cervix can get torn again during subsequent foaling and require lifelong postpartum reconstruction.

Veterinarians have several surgical options when it comes to compromised perineal conformation in mares, depending on the affected structures. Biologically, the mare is equipped with three protective barriers to separate her uterus from the contaminants of the outside world: the vulvar lips, the vestibulovaginal fold, and the cervix.

When one or more of these barriers gets compromised, air and feces, along with the bacteria they contain, can enter and contaminate the vagina and uterus. Likewise, urine can pool in the uterus. This increases the risk for vaginal and uterine inflammation and infection, which are not conducive to conception. The role of surgery is to restore the integrity of the mare’s protective barriers. Pasch described five common elective surgical procedures for mares, all of which can be performed in the standing horse under sedation:

• Caslick’s (vulvoplasty). Commonly performed as a preventive measure, this simple, routine procedure, involves suturing the dorsal (upper) portion of the vulvar lips to prevent air aspiration and fecal contamination. The goal is to reinforce the protection the vulvar lips provide. The veterinarian must manually open the Caslick’s before foaling and repeat the procedure each year the mare foals.
• Deep Caslick’s (episioplasty, aka Gadd technique). A more invasive adaptation of the Caslick’s, this two-layered procedure involves suturing the vestibular mucosa in addition to the vulvar lip mucosa. The goal remains the same: Prevent vaginal contamination from air, feces, and other foreign matter.
• Perineal body transection (perineoplasty aka Pouret operation). Reserved for mares with severely altered perineal conformation, this rather invasive procedure involves completely reconstructing the perineal body to allow the vulva to return to a more normal, upright position. It can be a good option for mares with vulvas that deviate so far from the normal, upright angle that even a deep Caslick’s isn’t enough to prevent contamination.
• Urethral extension. When the mare’s anatomy makes it such that urine gets into the vagina—a condition known as vesicovaginal reflux—she’s at risk of developing urovagina and urometra (urine pooling in the vagina and uterus, respectively). Using the mare’s own vaginal and vestibular mucosa, surgeons can fabricate a tube that acts as an extension to the urethra, allowing urine to be expelled out of her body instead of stagnating in her reproductive
• Endometrial cyst removal. Cysts in the uterus can interfere with embryo fixation, maternal recognition of pregnancy, and uterine fluid clearance. They can be problematic when numerous, large, and/or located near the cervix or a uterine horn base. Veterinarians have several options for this procedure: manual removal with a snare or biopsy forceps, hysteroscopy-assisted laser removal, and hysteroscopy-assisted electrocautery snare.

For mares deemed infertile because of inadequate perineal conformation, elective surgery can allow them to conceive and carry foals again. Having an honest discussion with your veterinarian ahead of the procedure will ensure your expectations are in line with the surgery’s purpose and likely outcome.