Castration in Horses

Courtnee Morton, DVM
By Courtnee Morton, DVM on Dec. 14, 2022

What is Horse Castration?

Castration is the term used for the removal of testicles in horses, similar to the word “neutering” in dogs and cats. This procedure can be done with the horse either standing, or recumbent (laying down), either on their back or on one side. Intact male horses are referred to as stallions; once they have been castrated, they become geldings.

When Should a Horse be Castrated?

Horses can be castrated once both of their testicles have descended, which usually happens by 6-12 months of age. The “recommended” age for this procedure may vary depending on your horse’s intended use, size, and behavior. Some people may want to let their horse mature before castration for a more pronounced jawline and muscle development, or if they intend to breed or collect semen for shipped artificial insemination (AI) before using them for a different purpose.

Testosterone is responsible for stallion-like behavior, and secondary sex characteristics such as thick muscling and pronounced jowels. In general, stallions or studs are much harder to handle and require different management than geldings. If they are housed near mares, they may be easily excitable, and try to jump through fences to breed a mare in heat. They often require solitary confinement or separation from other horses, as they can also be combative towards other stallions and geldings. The high amounts of testosterone coursing through a stallion’s body often overrules reason and manners.

If your horse is not intended for breeding, most veterinarians recommend your horse be castrated before maturation, and before the onset of most stallion-like behavior; typically, at one to one and a half years of age. This is a straightforward procedure that horses recover from without issue, that then makes life simpler for both your horse, and those that handle him.  

Does Castration Hurt Horses?

The procedure itself is not painful for the horse. This procedure can be done in the field if both of the horse’s testicles are descended, or can be done in a hospital setting. Most castrations are performed recumbent, with the horse asleep.

They are given a “pre-med” dose of sedation, then after a few minutes they are given the tranquilizer, sometimes in addition to another type of sedative which aids in a smooth recovery or “waking up” process. This combination typically keeps most full-grown horses asleep for around 15 minutes which is more than enough time for a routine castration; some horses may try to wake up sooner and require additional “top-ups” of sedation during the procedure.

Banamine, an anti-inflammatory, is also usually administered at this time to help with any potential pain. The testicles may be injected with lidocaine, a local numbing agent, for this as well; it also helps keep the horse asleep and less reactive during the procedure, so they do not need additional doses of sedation.

For a standing castration, horses will be given a pre-sedation dose typically, without the ketamine that makes them lie down. Then, a twitch is typically applied to distract the horse while lidocaine is administered into the testicles. This will keep the horse from being as reactive and trying to kick and move during the procedure, which is important for safety and to prevent premature tissue removal and bleeding.

Castration Methods

There are a few different approaches your veterinarian might take when it comes to castrating a horse.

Emasculators are a commonly used tool used to cut the musculature and clamp the vessels leading to the testicular area. Depending on the age or breed of your horse, sometimes a ligature, or suture, will be tied around these prior to using the emasculators to prevent any bleeding. This is commonly done with older horses with larger vessels, and in donkeys, as they typically have more fat in the area and a higher tendency for bleeding.

The other common method for equine castration involves the use of a twisting or spinning action; this may be done with an Equi-twister, which clamps the testicular tissue, and then is manually twisted to slowly cut off the blood supply.

The other option is the Henderson technique, which uses a clamp attachment for a drill. While this sounds intense, this method is faster, involves less swelling, and less bleeding than the traditional method.

Unless the castration is cryptorchid (with undescended testicles in the abdomen that must be surgically retrieved), the surgical incision is usually left open. This is to facilitate any drainage that may occur; if this incision were to be closed using sutures, any blood build-up that occurs is a breeding ground for bacteria, and post-operative infection rates are greatly increased. Your horse is typically given a tetanus vaccine at the time of castration, along with antibiotics. It is important to follow your veterinarian’s post-operative instructions carefully to prevent any complications.

Potential Complications of Castration in Horses

  • Bleeding: large vessels in mature horses which can be hard to close off, inadequate tissue clamping, or intense activity after castration can sometimes lead to bleeding. The common rule for bleeding in the first 24 hours is if you can count the drips, it’s ok; however, if the bleeding becomes too quick to count or a steady stream, call your veterinarian immediately.

  • Herniation: Sometimes a stallion will have large inguinal rings, which are the spaces separating the abdomen and the scrotum. This can allow for sections of intestine to potentially fall through the ring and the surgical opening. If you see anything resembling loops of sausage or other tissue protruding from the surgical site, call your veterinarian immediately.

  • Proud cut: “Proud cut” is the term used when not all the testicular tissue is removed during castration. While this is much less common than it used to be, this can be a potential complication. Proud cut may lead to continued testosterone production, so you could notice persistent stallion-like behavior. This can be confirmed with a blood test checking your horse’s testosterone levels. If your horse is castrated late in life, their studly attitude may continue regardless, as much of this is learned behavior.

What To Do After Castrating a Horse

It is important to follow your veterinarian’s post-operative instructions after castration. This typically involves light hand walking or exercising for a few days, with a gradual increase. Movement is important to allow drainage at the surgical site. Leaving a horse standing in a stall for days after castration often leads to severe swelling of the area, which becomes painful, and potentially infectious. This may require potential debridement or removal of infected tissue by your veterinarian, more antibiotics, and cold hosing the area daily along with exercise to help reduce the swelling and potential scirrhous cord formation. This is when some of the tissue becomes hardened and infected, and there may be chronic drainage from the area.

Full recovery typically takes about two weeks if no complications arise; it’s important to keep newly gelded horses away from mares for the first several weeks as there are still high levels of testosterone circulating in the body, and they can still impregnate a mare potentially after 30 days after castration.

Behavioral Changes After Castration

In time, your horse will have less “studly” urges, unless your horse was very mature and had been used for breeding prior to the castration. Over time this will lead to less reactiveness to mares, a generally calmer demeanor, and less aggression. Older stallions are less likely to change their attitude, as many of their behaviors are learned.

Featured Image:

Courtnee Morton, DVM


Courtnee Morton, DVM


Dr. Courtnee Morton is a 2017 Ross University School of Veterinary Medicine graduate. Since graduation, she completed an equine internship...

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