Castration is a surgical procedure performed by your veterinarian that can help eliminate unwanted aggressive male behaviors and prevents the animal from reproducing. Castration is also known a gelding, cutting or emasculating. Castration of the horse is a common surgery that removes the testicles of the male horse. The testicles produce the hormone, testosterone that develops the masculine state of the male. Testosterone is the hormone that gives the male horse the large neck, more heavily muscle appearance and aggressive behaviors. Castration is used to control the aggressive behavior. Although castration is a common surgery performed by veterinarians, it should not be considered routine. There are many complications that can occur and some can be life threatening to the horse.

The procedure itself involves the removal of both testicles from the horse under general anesthesia positioned on his back or heavily sedated and twitched while standing. The castrations we do at Equine Medical Service are always done under general anesthesia, with the horse positioned on his back. Using either method the basic procedure is the same. An incision is made over each testicle through the scrotum. Then the tissue surrounding the testicle is separated away and the testicle and spermatic cord are exposed along with the cremaster muscle. Contained within the spermatic cord is the blood supply, nerve supply and ductus deferens of the testicle. The cremaster muscle is attached to the outer tissue of the testicle, raising or lower it within the scrotal sac to maintain the proper temperature of the testicle. Once exposed, the spermatic cord is crushed and severed by a surgical instrument called an emasculator. Emasculators function so that when the handles are closed, one side of the instrument it will crush one side of the cord while the opposite side is cut. The crushing action keeps the severed vessels from bleeding without having to tie them off with suture material. In younger immature colts the cremaster muscle is included in the emasculators without having to separate that cord from the muscle. Unfortunately, in older horses that are more mature, there is a need to separate the cord from the muscle, as well as separating the ductus deferens from the vessels. This larger amount of tissue does not allow for an adequate crush on the vessels, especially the artery, and the horse is then at risk from bleeding to death internally. Also, by separating the different tissues the abdominal cavity is entered and this creates a serious risk for a complication called eventration. Eventration is when a portion of the small intestine comes through the inguinal canal into the scrotum and out the incision. (These and other complications are discussed more in depth below.) Once both testicles are removed and bleeding form the cord is not a concern, the horse is recovered from anesthesia and stall confined for a minimum of 24 hours. After that time, the horse needs to be exercised to control the swelling that will occur around the incision and sheath area.

For all castrations that are performed in the field versus in a surgery suite, the incisions are left open to heal from the inside out. This is done because of the less than sterile environment under which castrations are performed. Under certain circumstances castration in a surgical suite is absolutely necessary. One such circumstance is when a male horse has one or both testicles in the abdomen as opposed to in the scrotum. This term is called cryptorchidsm. This is also known as a crypt, a rig or ridglings. Normally the testicles of the foal descend from the abdomen into the scrotum, before birth or just a few weeks after birth. When the descent does not occur then the testicle has to be found within the abdomen for removal. Some foals that do not have a palpable testicle in the scrotum may have the testicle descended from the abdomen but the testicle lies in the inguinal canal. This is termed a “high flanker”. These are not as difficult to remove as cryptorchid, but are more complicated than a routine castration. The best way to approach these surgeries is to prepare for the worst, but hope for the best and do them in a surgical suite.

As with any surgical operation there are several complications that can occur. As mentioned before one complication is eventration. Intestinal eventration is a serious emergency and can be life threatening. Omental eventration is when the omentum comes through the inguinal canal and out the incision. The omentum is a fatty yellow tissue that surrounds the abdominal organs. This condition is less serious than intestinal eventration but must be handled quickly to prevent an ascending infection. The horse must be anesthetized again and the omentum emasculated just in side the incision. Another complication is excessive bleeding. Some small drips of bleeding will normally occur from the incision. Steady dripping or a stream of blood is considered excessive bleeding. If the bleeding persists, the horse may need to have the incision packed with gauze to control the bleeding. If the bleeding is severe enough, the horse may need to be anesthetized again and the offending blood vessel tied off to prevent further bleeding. It is normal and expected to have a certain amount of swelling in the post-operative period. However an extreme amount of swelling can indicate there may be an infection brewing. An infected incision site that could lead to an infection of the remaining spermatic cord can be a severe complication to castration. This can occur when the incision closes from the outside first, trapping blood, serum, and any bacteria in the incision. This is the perfect scenario for an infection to start. The horse will be treated with antibiotics and have the incision site re-opened to allow it to drain. If the remaining spermatic cord becomes infected then it must be surgically removed.

Horses can be castrated as early as a few days to any age after that. The most common time to castrate is prior to weaning through the age of two years. The older and more mature the horse, the more complications can occur. It is true that gelding a horse at a younger age the taller the horse will grow. The removal of testosterone delays the closure of the growth plates of the bones and allows the horse to attain a taller stature. It also decreases the amount of muscle mass the gelding will develop, but in the same light prevents and eliminates the aggressive behaviors that intact males can have.

Castrations are a necessary elective surgery. Although complications can occur, castrating males at a younger age can minimize these problems. One can also prevent behavior problems from starting by castrating the horse at a younger age.