Veterinary Corner 12/97: Castration
by Katherine Burnett, DVM
Edgecliff Equine Hospital
S. 1322 Park Road, Spokane, WA 99212 * 509/924-6069
e-mail: kburn10681@aol.com
A stallion should be an outstanding example of his breed. This is very important, since potentially he can breed hundreds of mares in his lifetime, affecting the gene pool significantly more than a mare, who can have a maximum of one foal per year. Additionally, stallions can be aggressive toward handlers and other horses, and unless managed carefully can escape confinement and seek random mares to breed, thus producing unwanted pregnancies. For these reasons, castration is the most common surgery performed on the horse.Much controversy surrounds the decision about the appropriate age for castration. Most colts have reached puberty by the age of 18 months. Most veterinarians agree that there is no advantage, and, in fact, are disadvantages to waiting beyond this time. Once colts have reached puberty they are often difficult to handle, and must be separated from the group in order to prevent fighting and unwanted breedings. Colts well in to puberty have larger testicles with a more extensive blood supply: hence, they are more apt to bleed following surgery. In addition, studies have shown that colts castrated well before puberty (in some cases as early as 3 to 4 months of age) are just as tall and have bone structures that are just as large at maturity as those horses castrated as two year olds or older. Some veterinarians have noticed an increased incidence of hernias as a complication of castration when it is performed before 6 months of age, however. Given these facts, it appears that the optimum time for castration is after 6 months of age but before 18 months.
Castration is a routine procedure if both testicles have descended in to the scrotum. Before puberty the testicles may be too small to be seen, but can be felt. If they have not descended in to the scrotum, and time (rarely, it can take up to 5 years for testicles to descend!) does not rectify the problem. A more extensive "cryptorchid" surgery is required in the hospital.
Testosterone, the hormone responsible for male breeding behavior and some forms of aggression, diminishes to minimal levels within 48 hours of surgery. It is possible for geldings to exhibit stallion-like behavior, including breeding mares. It is extremely rare to find that one of these horses has been improperly castrated, a condition commonly known as "proud cut."
If the horse is extremely aggressive, hormone tests may be indicated to determine whether or not a retained testicle is present. Most stallion-like behavior in the gelding is attributed to a small amount of testosterone secretion by the adrenal glands near the kidney. Management usually involves separation from mares, if necessary, and sometimes hormone treatment. Since the adrenal glands are necessary for life, they cannot be surgically altered.
