Equine and Camelid Castration

Equine Castration Overview


Most colts are castrated between 6 months and 2 years of age (ideal age for castration is closer to 1-1.5 year). Stallions can be ridden and trained but do need special housing, care and handling. Most adult horses are castrated. This minimizes the dangers and decreases the number of unexpected pregnancies. Younger horses can be very challenging to castrate as it does help to have testicles big enough to stay in the scrotum. Smaller testicles can be harder to remove and are more easily confused with other structures (including the penis).

Testosterone is responsible for the male sexual characteristics in horses, including the muscular jaw, neck and body. Animals that are castrated while still growing develop longer and straighter limbs due to the later physeal (growth plate) closure. Equine castrations are typically performed on colts between 6 months and 2 years old. This increases the height of the horse compared to earlier castrations. Horses castrated too early may actually develop orthopedic issues (arthritis) due to the straighter limb conformation.

The procedure is usually done on the farm where the colt lives. Supplies are only those brought with you on your truck. Due to variability in horse responses to handing and anesthesia as well as to challenges of working outside, make sure your truck is stocked with double what you anticipate needing!

Castration steps

The following is a rough outline of the process. Please refer to the following chapters for more details.

Ensure the colt is healthy, manageable and has two testicles

Do a thorough examination including palpation of the testicles if possible.

Castration is an elective procedure. The horse should be vaccinated (especially for tetanus) and not show any signs of illness. This is not a time to halter break a colt if there are any alternatives. How much the horse has been handled and his response to handling is really nice to know in advance of the surgery day. Yes, he has a halter on but does he actually respond to signals?

Horses are rarely monorchid but can have delayed or inhibited testicular descent (cryptorchidism). It is imperative that either both or no testicles are removed. Leaving one testicle for a later procedure is considered both unethical and unwise. The horse appears to be a gelding but can act like a stallion. Records are not usually reliable enough for a surgical approach and can be separated from the horse. Do not remove a lone testicle. If you think you have two testicles, remove the less obvious one first. You can always stop and wake the horse up if it is not truly a testicle.

Decide on recumbent or standing castration, location, and roles

Most surgeons have a preference for either recumbent or standing castration. Both work. Sometimes a situation or horse characteristics means one is a better option.

A grassy field away from cars, roads, buildings and other animals is best.

Your client should play a minimal role; use your technician, vet student or prevet student for any horse handling.

Administer preoperative medications

Horses should receive an NSAID preoperatively. Antibiotics do reduce the risk of postoperative complications but are not required. Tetanus vaccination should be up to date (within 6 months) or boostered. If the horse is unvaccinated, it is better to vaccinate and wait. Tetanus antitoxin carries it own risks.

Place an iv catheter if desired (a good idea unless you have a donkey or a miniature stallion – sometimes those aren’t worth the effort).

Sedate or anesthetize the horse

This includes placing a local block in the testicle or spermatic cord.

Castrate the horse

Castration may be performed via an open or closed method, depending on whether the vaginal tunic is cut to expose the testicle (open) or removed with the testicle (closed). In most cases, an incision is made over each testicle. Testicles are removed after each artery is ligated, crushed and/or twisted to create hemostasis. The incisions are left open for drainage. Before the horse wakes up, other procedures may be performed such as hoof trimming or wolf tooth extraction.

Recover the horse

The horse is allowed to stand on its own time (if recumbent) and allowed to return to its stall once able to walk safely.

Educate the client on postoperative care

Most horses are stall rested for the remainder of the day. The colt can be fed once he is fully awake. After the first day, the colt should be exercised to keep the surgical site open and draining. Too much swelling will cause the incision to seal together and prevent that drainage. If not draining, the area can readily become swollen and/or infected. NSAIDs help decrease swelling and encourage exercise. A horse turned out on its own and in pain is unlikely to exercise.

Horses may retain stallion like behavior even after the testicles are removed; however, most lose the behavior after a few days or weeks. New geldings can remain fertile for several weeks (it depends on if they have viable sperm in the epididymis at castration and if they ejaculate or not). New geldings should be separated from mares for at least two days; many recommend two months to be totally safe.


This video gives a general overview of the process (4 min)

Castration in the horse, The Horse, 2001 – nice overview written for clients

Castration complications: A review of castration techniques and how to manage complications. VCNA (2021): 37:259-273

    • Note- Please continue NSAIDs for 3 days postoperatively and most horses that develop infections due to premature scrotal closure do not need antibiotics, just drainage.


Icon for the Creative Commons Attribution-NonCommercial 4.0 International License

Large Animal Surgery - Supplemental Notes by Erin Malone, DVM, PhD; Elaine Norton, DVM PhD; Erica Dobbs, DVM; and Ashley Ezzo, DVM is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License, except where otherwise noted.