Castration in Horses

Questions and answers on horse castration

  • First of all, what is castration?
  • Why do we castrate male horses?
  • What should I consider before getting my horse castrated?
  • Is it better to have my horse castrated when they are standing?
  • What happens when my horse is castrated?
  • What happens after my horse is castrated?
  • How soon can I exercise my horse after he is castrated?
  • What complications can occur after my horse is castrated?
  • What happens if my horse is a cryptorchid?
  • Conclusion

First of all, what is castration?

Castration refers to the removal of the testicles in male animals. Also called “gelding” and “being cut”, castration is a common procedure carried out in male horses. However, even though it is commonly performed, there are still some important factors to consider before getting your horse castrated.

Why do we castrate male horses?

The most common reason for castration is to control breeding and reproductive or aggressive/assertive behaviour in colts and stallions, especially if they are to be housed with fillies and mares.

There are several other reasons why a male horse might be castrated, including medical reasons such as if the testicles have been damaged due to injuries from trauma, inflammation, infection, or even because of testicular cancer. One of the most common medical reasons for urgent castration is because of trauma, and often this is because a stallion has injured his testicular/scrotal area trying to get into a field of mares!

In some horses, there can be retention of one, or even both, of the testicles within the abdomen after puberty. This is called cryptorchidism and surgical removal of both testicles is always recommended in these animals (more on this later).

What should I consider before getting my horse castrated?

The usual recommended age for castration of a male horse is between the age of 1-2 years of age. Puberty in horses usually starts at around 10-11 months of age, so we are attempting to castrate him before the full development of male behaviour patterns. Smaller ponies can go through puberty slightly younger than this, while big draught horses and cobs may be slightly older than this when they complete puberty.

In general, castration carried out at a younger age is more straightforward. This is because the testicles are smaller in younger animals, so the castration tends to be less invasive. An older stallion will also have less collagen in his skin and tissues, meaning that the castration can take longer to carry out, and healing can be slightly slower.

For an elective castration, it is recommended to book your horse in for the procedure either during early spring or late autumn. This is because there are fewer flies about to bother the castration site in these months, and thus the risk of infection should be lower. If your horse needs to be castrated urgently (such as because of medical indication) during the summer months, it is advised to organise stabling for them where they can recover away from the summer flies and other insects.

Your colt or (if being cut later) stallion should have a pre-operative examination by your veterinary surgeon to ensure they are fit and healthy for the operation. It is important to remember that all medical procedures carry some risks, especially when they involve sedation/general anaesthesia. Your vet will be able to discuss these with you and make recommendations for the best protocol for your horse. Your vet will also check that your horse has two normally descended testicles and that there is no sign of umbilical/inguinal herniation that may need to be corrected at the same time as the castration.

It is strongly recommended that you ensure your horse is up to date with their tetanus vaccination before the surgery. Horses are particularly prone to developing tetanus and they can contract an infection even if the surgery has gone smoothly and without complications. Tetanus in horses can be fatal.

Getting your horse insured is recommended for every owner. Ideally, you should take out insurance for your horse as soon as you acquire them. It is important to note your horse may not be covered for castration or complications of castration, and you should check with your insurance provider before surgery.

Is it better to have my horse castrated when they are standing?

In general, standing castration is not recommended by most equine veterinary hospitals and specialists. The main reason for standing castration not being recommended is safety. This includes the safety of the veterinary surgeon, horse, and their owner.

It is almost impossible to maintain the same level of sterility in a castration where the horse is standing as can be achieved in a recumbent (lying down) procedure.

It can be very challenging to adequately restrain the stallion during a standing castration. This means that the risk of infection, injury to the owner, the horse, and/or the veterinary surgeon are much higher with standing castration. Even adequately sedated horses can still place a well-aimed kick!

The risk of infection is significantly higher in standing versus recumbent equine castrations. In a UK-based study, it was found that stallions that had a standing castration procedure had a complication rate of 22%. This is significantly higher compared to the rate of 6% complications in horses that were castrated under general anaesthesia with surgical closure of the wounds.

There has been a longstanding concern with the rate of mortality (death) associated with general anaesthesia in horses for both vets and owners. While every general anaesthetic does carry risks, the modern development of techniques and drug use have significantly improved survival rates for equine general anaesthesia.

What happens when my horse is castrated?

Your vet will carry out a physical examination of your horse, including checking the genital area, listening to your horse’s heart and lungs, and choosing appropriate sedation based on your horse’s weight, age, and temperament.

The sedation is generally administered into your horse’s vein. Your vet will often place a catheter (cannula) into your horse’s jugular vein (a large vein in your horse’s neck) to allow them to administer additional drugs as needed throughout the procedure.

Many vets will have a veterinary nurse (or veterinary technician) to monitor your horse’s vital signs throughout the procedure and assist if needed throughout the surgery.

For a routine recumbent (lying down) castration, the procedure generally lasts between 10-30mins, although this will vary slightly from horse to horse.  When your horse gets sleepy from the sedation, anaesthesia will be induced. Once asleep, he will be positioned for the surgery. The surgery area (the groin and especially the scrotal skin) will be cleaned and surgically scrubbed to reduce the risk of infection.

Your vet will administer any additional drugs required, including local anaesthesia into the surgical area, called lidocaine. This will numb the area and help reduce the amount of sedation drugs your horse requires. This can make the risk of the procedure much lower.

With the horse adequately restrained with appropriate ropes and manual restraint for safety, your vet can begin the procedure.

Your vet will make two incisions in your stallion’s scrotum, to access each testicle. The testicles are then individually removed through a method of crushing the blood supply, tying off the blood supply with ligatures (surgical knots) and then removing the testicles and part of the spermatic cord attached to the testicles. Your vet may then close over the wound with stitches (sutures), but often the site is left open to prevent build-up of fluid. Your horse will be monitored during their recovery by either your vet or veterinary nurse.

What happens after my horse is castrated?

It is recommended that the surgical area is checked by your veterinary surgeon 24 hours after the procedure. This is to check for bleeding and any prolapse (exposure of tissues from inside the body) that may have occurred and need to be surgically repaired. Your vet will advise on the best recovery exercise for your horse and prescribe pain relief and anti-inflammatory drugs for 3 to 4 days after the surgery.

It is vitally important that your newly castrated horse does not have access to any mares after their procedure. There have been cases of geldings impregnating mares several weeks after they have been castrated! This is because there can still be some viable sperm in the remaining spermatic cord that is left after castration.

It is also worth keeping in mind that some geldings will continue to display stallion/male-type behaviour even after they are castrated. This may subside several months after castration, or in rare cases, it may continue long-term. If your gelding is still showing stallion-type behaviour even after they have recovered fully from the procedure, it is worth discussing with your vet about a blood test to check that no remaining testicular tissue is remaining at the surgery site. Your vet may also recommend behavioural training that your horse would benefit from if there is no medical reason for the behaviour.

How soon can I exercise my horse after he is castrated?

Your vet may recommend light exercise for your horse to reduce swelling following surgery. However, it is generally advised to wait at least 6 to 8 weeks before resuming normal training in a castrated horse. This is to allow the area to heal and reduce complications.

What complications can occur after my horse is castrated?

The most common immediate complication that can occur following surgery is bleeding (haemorrhage) from the spermatic vessels. Your vet should identify the problem and take any necessary steps to resolve the bleeding.

From 24 hours post-castration on, the most common complications are oedema and castration wound infection. Oedema (swelling and fluid accumulation at the surgical site) is very common for all ages of horses that are castrated but is often most common in older horses who have less collagen (elasticity) in their skin and tissues. If oedema occurs, your vet will advise on how best to manage it in your horse. This management may include cold hosing, a longer course of anti-inflammatories, exercise and possibly a course of antibiotics if it is suspected there is an infection present. Infection of the surgery sites is a fairly common complication that may occur but is usually treatable with a short course of antibiotics and management of swelling.

Other much less common complications include prolapse of tissues from the surgery site, chronic infection, problems with the penis (such as paraphimosis, where the penis gets stuck outside of its sheath and cannot retract normally), and tetanus. Contact your veterinary surgeon if you have any concerns about your horse in the post-operative period, as prompt treatment is essential for the best chance of making a full recovery. Good pre-operative preparation and carefully following the post-operative instructions from your veterinary surgeon can massively help to reduce the risks of these complications.

It is important to note that tetanus can occur up to three weeks after your horse has been castrated. Tetanus has an extremely poor survival rate, so prevention of tetanus with vaccination is always recommended before any surgery on your horse.

What happens if my horse is a cryptorchid?

If your horse is a cryptorchid (also called a rig if both testicles are not in the scrotum), it is strongly recommended not to breed from him and to instead have him castrated, with both testicles removed. This is because cryptorchidism is genetically carried and can be passed to offspring. Horses with retained testicles are also at significantly higher risk of developing testicular cancer (especially “teratomas”). This is probably because the testicles remaining within the body will be exposed to the higher core body temperature than testicles that normally descended into the scrotum. Cryptorchid and rig horses are also more likely to have unpredictable behaviour and, in some cases, may still be able to get mares pregnant.

Some horses’ undescended testicle(s) may simply be in their inguinal canal (groin area) and can be identified by your veterinary surgeon and removed with an incision over this area during the usual castration procedure. More often, though, cryptorchid surgeries require referral to a specialist equine hospital like ours, where a combination of ultrasound and keyhole (also called laparoscopic) surgery can be carried out to identify and remove the errant testicle(s). Your vet will advise on the best protocol on how to castrate your cryptorchid/rig horse, depending on their physical examination and their temperament.


Getting your horse castrated comes with many benefits, but there are lots of things to consider before booking your horse for the procedure. Castrated horses (geldings) are often more laid-back, predictable, and calmer animals, who can be housed safely with mares. They are generally easier to handle and less likely to display aggressive behaviour. However, as discussed above, it is recommended to have a comprehensive discussion with your veterinary surgeon to make an informed decision that is best for you and your horse.

References/Further Reading

Schumacher J. Testis. In: Auer JA, Stick JA, Kummerle JM & Prange T ed. Equine Surgery. 5th Edition Elsevier; 2019: pp994-1034

Mason BJ, Newton JR, Payne RJ, Pilsworth RC. Costs and complications of equine castration: a UK practice-based study comparing 'standing non sutured' and 'recumbent sutured' techniques. Equine Vet J. 2005 Sep;37(5):468-72. PMID: 16163951.

Brinsko SP. Neoplasia of the male reproductive tract. Vet Clin North Am Equine Pract. 1998 Dec;14(3):517-33. doi: 10.1016/s0749-0739(17)30184-0. PMID: 9891722.

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