11th June 2019

Like dogs and cats, there are many medical and behavioural benefits to having a castrated horse, a gelding, compared to keeping a stallion. If you are planning to breed from your horse then clearly castration is not a consideration but if you are not, castrating your colt or stallion is strongly advised. Stallions can be aggressive, territorial, difficult to handle and usually require specialist stabling and field management.

Castration is considered a routine surgical procedure and usually goes without a hitch. It can be done under general anaesthetic or standing, this is usually decided based on vet preference, size of horse, age of horse, temperament of horse and facilities available and a discussion with your vet will determine which approach is most suitable.

Entire male horses can be castrated at any age and at any time however spring and autumn are preferable as there is less/no mud but complications from fly interference are reduced. Horses that are never going to be considered for breeding are traditionally castrated in the spring of their yearling year, assuming that both testicles are descended. If both testicles are not descended into the scrotum, the horse is called rig and in this case the vet may decide it is worth waiting a little while to see if the retained testicle descends or the horse will need to be castrated in a hospital setting.

Standing castration will be performed in the field and is often chosen to avoid a general anaesthetic risk. The process usually does not take very long and provided there are no complications, the horse will not require box resting. This is because the surgery involves opening the scrotum, removing the testicles and leaving the wound open to drain with no stitching at all. It is encouraged that the horse moves in the post-operative period to minimise swelling and drainage of the site. It is important to note that standing castration in the field is a clean procedure but not sterile, it is not possible to achieve a 100% sterile environment, but your vet will do as best they can. Your vet may also choose to prescribe antibiotics, this will be based on personal preference and on individual circumstances.

General anaesthetic can be performed in the field or in a hospital setting and is determined on a case by case basis. Whilst there is sometimes an increased cost involved in a general anaesthetic, a vet would not be suggested without sufficient reasoning and pushing for a standing castration to save money may result in serious complications. Horses more suited to castration under general anaesthetic would be those older than 4 years of age, certain breeds such as arabs or some draught breeds who have an increased risk of evisceration, donkeys and particularly small breeds purely due to logistics. There are two techniques of castration under general anaesthetic, open as with standing (the preferred option if general anaesthetic was only selected due to temperament or size) or closed, this is where the vaginal tunic is opened to allow removal of the testicle and then closed again with sutures. This is avoids the risk of evisceration and herniation but must be performed in an adequately clean environment i.e. a theatre, as closing the incised layers stops drainage and therefore stops the wound cleansing itself.


Risks and complications can occur with any surgical intervention, those outlined below are most commonly seen following castration.

  • Infection – can occur from any kind of contamination during or after surgery. It is the most commonly seen complication is easily rectified if spotted in good time, things to look out for are tenderness around the surgical site or sometimes lameness, increased temperature or purulent discharge.
  • Bleeding – also a common complication, more often associated with the open technique. Your vet will outline what they deem to be an acceptable level of bleeding and when to be concerned, it is rare but bleeding following castration can be fatal. Generally, if you can count the drips there shouldn’t be too much cause for concern but if in any doubt, call for advice.
  • Post-operative swelling – should reach a maximum at roughly 5 days post surgery and is to be expected to a degree. Gentle exercise e.g. turnout (if sensible) or time on a walker should help to minimise this problem.
  • Evisceration or herniation – the most severe and worrying of complications. If at any point you notice anything hanging from the surgical site, you must call your vet and whilst you are waiting, try to keep the horse settled and restrained. It may well be that it is nothing of concern, for example a piece of omentum but if it happens to be small intestine things can progress very quickly. The peristaltic action of small intestine means that it will continue to come out of the incision and contamination or breakage of the small intestine is life threatening. Your vet will advise you over the phone how best to provide first aid while they are on their way to you.


A final thing to note is that since castrations are often performed on young animals, they may have not begun a vaccination protocol, this means it is important that they are covered for tetanus, this can either be with a tetanus only vaccine or tetanus antitoxin. If you have any questions regarding castration, your vet will be more than happy to answer them and discuss any worries that you have.