Q. My stallion is going in for a cryptorchidectomy surgery (removal of a retained testicle). He has never bred any mares and is well behaved. This spring, his testicle started swelling on hot days and my veterinarian recommended the surgery. What is the expected recovery time and how long do I need to wait until I can turn him out with mares? He has been turned out with geldings in the past and never caused trouble. How long should I wait to get him back into training?

—Abel

A: It is recommended that stallions with only one testicle in the scrotum be castrated, as the horse might be more prone to testicular cancer. It is not uncommon for the scrotum to fill with fluid when the days are hot (this is called hydrocele). The exact cause isn’t known, but it appears that peritoneal fluid from the abdominal cavity leaks into the vaginal tunics during hot weather, causing the scrotum to swell. There is concern that the excessive fluid around the testes will cause “heat stress” to the testicle and decrease sperm production. Research indicates that a decrease in sperm production might occur.

As the horse has a retained testicle in the abdomen, he will need a longer recovery time than if both testes were in the scrotum. The veterinarian performing the surgery would be the best person to discuss the time off training. A guideline would be hand walking and hydrotherapy for two to three weeks, with full work in six to eight weeks. The horse can be turned out with mares in six weeks. If the horse showed stallion-like behavior before removing the testicles, he might still do so after testicle removal as mounting and erection is a learned behavior. If the horse did not behave in this manner before castration, he should not do so after the surgery