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