The procedure, which carries his name, was developed by Dr. Caslick (a French veterinarian) in the early 1930's. It was developed in response to genital infections in mares (primarily Thoroughbred mares) who had conformational abnormalities, or otherwise experienced a high frequency of genital infections. Although the procedure is related to a mare's reproductive health, it is not specifically indicated in equine breeding.
The vulva is the first line of defense against genital infections. The vulva is normally vertical, with the lips full and firm and meeting evenly in the midline creating a seal to exclude contaminants, such as feces dropping from the anus which is located directly above the vulva, or bacteria laden air, from entering the genital area.
There are a variety of reasons for the vulval seal to fail. During estrus the vulval lips become elongated and relaxed to allow for breeding, and thus the seal may be somewhat ineffective and could allow contamination from which a uterine infection may occur. This is not common however, and there are two additional barriers within the genital area to help prevent infections.
In some mares a conformational abnormality exists where the vulva becomes angled inward toward the body, and thus when defecation takes place, the feces are more likely to briefly lie across the vulval lips. In addition, if this angle is severe, the upper portion of the vulval lips become stretched across the pelvic brim, further decreasing their ability to create a good seal. There are mares (generally older, thinner mares) who have a relatively normal vulval conformation, however the anus is sunken in toward the body, resulting in most of the feces and accompanying fluids, passing across the vulva rather than dropping straight to the ground, and creating a constant source of contamination if the seal is not tight. Also in some mares who have had a large number of foals, the vulva may not return to its normal configuration, and the seal is not maintained due to stretching and scarring from previous Caslicks or other minor lacerations.
In young otherwise healthy mares who are rather lean, and in hard work such as race training, the vulval seal may be broken with exertion, and air allowed into the genital area. This often creates a noise known as wind-sucking and may result in genital infections. This is a problem for the owner and trainer in maintaining a training scheduole, particularly if the infections are recurring, and thus the procedure is commonly used in racing stables.
The Caslick's Procedure consists of suturing the upper portion of the vulval lips to assure an airtight seal regardless of condition, work, or conformational abnormalities. The lower one third of the vulva is not sutured to allow for urination. The procedure entails numbing of the vulval lips, trimming the left and right edges with scissors, and then suturing the open edges together tightly. This wound usually heals well in two to three weeks with minimal care and performs its function well in preventing genital infections.
However, many people have the Caslick's Procedure performed on mares routinely, without regard for their condition, the type of work they will do, actual conformation or any other factors. While it is not particularly harmful, it is often unnecessary. In addition, if the mare is to be used for breeding, the Caslick's must be opened for breeding, then reclosed when the mare is confirmed pregnant, and opened again well before foaling in order to assure tearing doesn't occur, which may require extensive repair, and can cause its own set of problems in the vulval area..
In an otherwise healthy mare in good condition, with no history of genital infections, and a normal appearing vulva, the Caslick's should not be routine. Many breeders of non-racing horses have bred mares for generations without using the Caslick's and without experiencing a unusual rate of genital infections in their mares.
Some individuals have reported that the Caslick's was performed after breeding to assure that the mare did not lose her foal. However, the procedure only prevented infections, some of which can result in an aborted fetus.
Since history indicates an increased risk for fillies in race training, many owners do routinely have Caslick's performed, however, when she leaves the track, it is no longer necessary. It can remain in place, or be opened if the mare is to be bred, but need not be reclosed after breeding. If a mare, for whatever reason, makes the wind-sucking noise, which can be a concern in a show horse, the Caslick's procedure will resolve the problem and eliminate the noise.