Closing the Door to Problems

One of the most frequent terms you will hear used by veterinarians during breeding season is Caslick's. This mare needs one, or this mare is due to foal in 16 days and her Caslick's needs to be opened. If you are not familiar with broodmares, or haven't spent a lot of time around them, then this term might be unfamiliar.

What is a Caslick's Procedure?

In a 1937 volume of the Cornell Veterinarian, E.A. Caslick, DVM, a native of upstate New York and graduate of Cornell's College of Veterinary Medicine, reported his surgical technique and the thought processes that led to the technique's development. The Caslick procedure of surgically closing the upper part of the vulva has been commonly practiced on many broodmares for the past 60 years. The procedure evolved in an effort to treat what Caslick had observed as the negative effect that air had on a mare's reproductive system.

"Early in my experience with the treatment of genital infections, I recognized air as a factor," he wrote. "Mares that were placed on treatment (for genital infections) apparently became worse for a short period of time and then their condition remained quite constant. If these same mares were allowed a period of rest, an immediate improvement would be observed."

It was a suspicion of Caslick's that the treatment-related introduction of air into the reproductive system was doing more harm than the specific treatment was doing good.

"The last case of this infection I encountered was in 1927," Caslick wrote. "At that time I became firmly convinced that the admission of air into the vagina by constant treatment was detrimental, so I discontinued treatment of the mare and closed the dorsal (upper) half of the vulvar opening (the first Caslick's procedure). In two months, this mare was normal and negative to culturing (for bacteria in the reproductive tract)."

Why is a Caslick's Performed?

There are several conditions that might require a mare to have a Caslick's procedure performed. The main reason a Caslick's procedure is recommended is due to pneumovagina (aspiration of air into the vagina, or windsucking). Pneumovagina can happen in a number of situations. In some mares, as they get older and if they have had multiple foals, their perineal conformation predisposes them to pneumovagina. In breeding mares, this can lead to not only the aspiration of air, but also of bacteria, leading to inflammation of the vagina (vaginitis), which can then extend to the cervix (cervicitis) and possibly into the uterus (endometritis). These conditions can make successful breeding of a mare very difficult. To prevent pneumovagina and all these possible aftereffects, a Caslick's procedure can be performed.

Many racing fillies and mares will also have undergo Caslick's procedures, not because of breeding soundness, but to prevent pneumovagina. There are no negative consequences to having a Caslick's long-term.

How is a Caslick's Performed?

A Caslick's procedure is a simple surgical procedure performed by a veterinarian using only local anesthesia. The mare is restrained in a set of stocks or in a stall and the tail is tied out of the way. In some instances, the mare might require light sedation. After the mare's vulva is cleaned, a local anesthetic is injected into both sides of the vulva. After the skin is anesthetized, a small strip of skin is removed from each side of the vulva. The two resulting edges are sutured together, leaving the bottom part of the vulva open so that the mare can urinate normally. The skin sutures are removed in 10-12 days if non-absorbable sutures are used. After the skin is healed, it creates a barrier to prevent the aspiration of air and bacteria.

Obviously, once a Caslick's procedure is performed and a mare becomes pregnant, then a few weeks before the mare is due to foal, the vulva will need to be opened. Otherwise, during foaling, the mare's vulva/perineum can be torn quite badly, leading to even more problems.

Take-Home Message

Whether you have an athletic filly, a racing mare, a breeding mare, or an older mare (whether being bred or not), a Caslick's procedure might be recommended to prevent problems in the reproductive tract. Ask your veterinarian if this simple procedure--done in the standing mare on the farm or at the barn--can be insurance against future reproductive tract infections in your mare.

Editor's Note: Thanks to Carol McLeod, DVM, of Versailles, Ky., for allowing us to photograph her performing this procedure.

Caslick anesthesia
The mare is restrained and/or tranquilized and her vulva cleaned and prepped, including local anesthetic.
Trimming the edges
The edges of the vulva are trimmed and sewn together to keep air and/or fecal materials from contaminating the reproductive tract.
Stitching up
While suturing the trimmed vulva edges, an opening is left at the bottom through which the mare urinates.
The result
The upper part of the vulva, once healed, is sealed against outside contamination. It must be opened shortly before foaling to avoid tearing.

About the Author

Christina S. Cable, DVM, Dipl. ACVS

Christina S. Cable, DVM, Dipl. ACVS, owns Early Winter Equine in Lansing, New York. The practice focuses on primary care of mares and foals and performance horse problems.

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