General Information

Castration involves surgical removal of the testicles. This surgery is usually performed one of two ways: standing under local, with sedation or under general anesthesia with the animal on its side (lateral recumbancy). The choice of how the procedure is performed is usually made based on the horse’s temperament, owner preference, veterinarian preference, or facility/location limitations. Regardless of the position of the horse, the procedure is basically the same with a few minor technique differences from surgeon to surgeon. The scrotum will be incised (cut open) over each testicle, or the botton of the scrotum can be removed completely (for inreased drainaged). The testicles are freed from their holdings and the mass of blood vessels are clamped (in rare occasions-ligated) and “crimped” to prevent bleeding. The testicles are completely removed and incisions are left open to drain. Post-operative bleeding is usually minimal. Recovery time varies between idividuals with most animals being completely healed within 2-3 weeks.

This surgery is performed on young colts or adult stallions to modify or prevent aggressive “stallion-like” behavior and pregnancy. We recommend that you wait to castrate your colt until they are at least 6 months old, but anytime after the testicles have “dropped” is acceptable. In normal colts, the testicles have descended into the scrotum by the time of birth, but in some colts one or both testicles does not completely descend into the scrotum and remains within the abdominal cavity or inguinal canal. Some horses can take up to two years for both testicles to descend into the scrotum where they can be removed routinely. Testicles that remain in the abdominal cavity, without descending into the scrotum, require a more complicated surgery to remove. These colts are commonly known as “rigs” or crytorchids. These animals can be referred to a surgical facility for a more invasive abdominal surgery to remove the testicles.

Before the surgery, the colt should be halter broke and accustomed to handling and bathing so they can be easily managed during and after surgery. Tetanus immunization is necessary before and at the time of surgery. It is highly recommended that your have at least two boosters of a tetanus vaccine or tetanus combo (EEE/WEE/Tetanus) prior to surgery.

Potential Complications of Castration

Although castration is a common surgical procedure and considered elective, owners need to be aware of certain complications that can occur during or after surgery. It is nearly impossible to predict if postoperative complications will occur. Your veterinarian should assess the animal to prior to surgery to limit any surprises including palpation of the scrotum in order to feel for any signs of current hernias. If a scrotal hernia is palpable, surgery should not be performed in the field.


Excessive bleeding can occur after castration of a horse with a clotting abnormality, abnormally large testicular blood vessels, and in certain breeds or individuals that have higher than average blood pressure (like donkeys and mules). The testicular blood vessels enlarge as a stallion ages. Thus, the younger the horse is when it is castrated, the less potential for postoperative bleeding. If a horse is over 2 years of age at the time of castration, control of bleeding is a greater concern and makes the surgery more time consuming.

Inguinal/Scrotal Hernia:

In some horses, the opening in the abdominal wall (inguinal canal) through which the testicles descend into the scrotum is abnormally large or flexible. In theses horses, the intestines and other abdominal tissue (omentum) can pass through the inguinal opening (herniate). Though inguinal hernias are very uncommon, they are a serious complication and require immediate transport to a surgical facility for correction.


After the testicles are removed, the scrotal incision is not sutured and is allowed to heal from the inside out. If the incision closes prematurely, infection can be sealed inside. If the scrotal area swells to approximately four times its presurgical size or if your horse’s rectal temperature exceeds 102 F, infection should be suspected. The aftercare instructions outlined below should help prevent infection. Hotter times of the year when flying insects are at their peak increase risks of infection and aftercare becomes critical to prevent serious infection.


Oh yes, it can happen! A recently castrated gelding can still get a mare in foal for some time after castration because of sperm remaining in the conducting system. Recently castrated geldings should be kept away from females for at least 60 days. I know this sounds unlikely, but believe me it is possible.

Post Castration Care

Conscientious postoperative care is essential for a smooth, uncomplicated recovery. The postoperative period also is a good time to begin daily training of your young horse.

Postoperative care is usually needed for at least 2 weeks after castration, so schedule the surgery for a time when this time commitment is not a hardship for you.  You should work with and handle your future patient before you have him castrated. This will make the aftercare less traumatic on him and you.
Stallion-like behavior does not always change immediately after surgery. Some cases can take months or occasionally a few geldings will show this behavior throughout their life. Owners should be aware of this possiblity and understand that it is an individual behavioral problem, not a result of a poorly performed surgery. On average 20% of all properly castrated horses will continue to act like a stud.

For the first 24 hours after castration, keep the horse confined and as calm as you can in a stall or small paddock. During the first 6 hours after surgery, look in on the animal every 30 minutes, then every 1 hour. Dripping of blood is expected, but the drips should be slow enough to count the individual drops. If the drips are coming too fast to count or blood is streaming from the wound, call your vet right away. Also call us if you observe colic signs or any dramatic increase in scrotal swelling or pink/red tissue protruding from the wound.

Starting the day after surgery, it is helpful to take the horse’s temperature before exercise. A rectal temperature over 101.5 is considered high and you should call your vet.   The after surgery exercise program should consist of 15 minutes vigorous, but controlled exercise. Lungeing or ponying at the trot is ideal. The horse may start out stiff gaited in the rear, but this should resolve quickly with exercise.  After exercise, cold-hosing is a great way to clean and reduce swelling, inflammation, soreness at the surgery site which will ultimately stimulate healing. Direct a stream of water (without the nozzle) against each side of the scrotum for at least 5-10 minutes. Let the water run from the side, not directly up into the wound (no pressure). If your horse is not used to a water hose, then you may have resistance to this at first, but it is essentail to a smooth recovery. I can’t stress enough the benefits of cold-hosing (hydrotherapy).
You can apply fly spray around the flanks and hindquarters,but Do Not spray directly up into the wound.

After the second day, the sheath and scrotum may swell up to 4 times its original size (grapefruit to small cantalope). This is expected. Usually postopearative swelling is reduced with exercise and cold-hosing. Everything should be back to normal after 7 days.

I highly recommend continuing the post-op regimen for a full 2 weeks, especially during the warmer months. Often everything is going great for the first 7 days and owners stop the exercise and cold-hosing only to have swelling and stiffness return with a vengence.

When To Call The Vet?:

You should call the vet that performed the surgery if….

You have any questions concerning your horse’s castration..
Your horse’s temperature is above 102F.
You observe excessive bleeding or drainage from the scrotal incision.
You observe any tissue hanging out of the scrotal incision.
Your horse does not appear to be recovering normally from this surgery or is not eating.