Equine Castration

Equine Castration

Castration is a routine procedure, where the horse is generally castrated for ease of management of the animal. Typically carried out from the spring of the yearling year, we prefer to castrate either in Spring or in Autumn, to try and avoid mud in the Winter and flies in the Summer. However, the procedure can be carried out at any time of the year if necessary.

Common Questions

Why should I castrate a colt?

If a colt is left entire it is usually impractical or impossible to run them in company, with either mares, geldings or other stallions, especially as they mature. They can become difficult to handle, and in some cases can be so dangerous as to pose a serious risk to the people and other horses around them. The added concern with an entire male is the risk of mares having an unwanted covering, resulting in pregnancy, either by an undesirable sire or when breeding was not even being considered.

How long does a castration take?

A castration usually takes about an hour, with the significant majority being at the owners premises where suitable facilities are available, or at the clinic if necessary.

When should I castrate my colt?

A colt can be castrated at any age. It is traditionally done in the spring of the yearling year, but in reality it can be performed earlier, as a foal, or later in life. There is a body of opinion that castration should be left as late as possible, in order to allow the horse to ‘mature’. However there is no evidence that foals left entire develop any differently from those castrated early. Indeed, on the continent it is common place for colt foals unsuitable to be kept for breeding purposes to be castrated when still suckling from the mare.

There is evidence to suggest that those foals castrated at such a young age recover from the operation faster and with fewer complications than their older counterparts. Colts can be castrated at any time of year; however they should ideally be castrated either in the spring or autumn, in order to avoid the flies of summer and the deep mud of winter, both of which can increase the risk
of post-operative complications.

Both testicles must have descended into the scrotum for a colt to be castrated. If only one is present (a ‘rig’), the owner is faced with two options: either give the colt more time in the hope that the missing testicle will eventually descend, although this does not always occur (if the testicle has not descended by one year of age, then it becomes increasingly unlikely that it will ever
“drop”); or taking the rig to a hospital for castration.

This may incur significantly more surgical intervention and cost, as the retained testicle can be anywhere from the inguinal ring (groin) to within the abdomen, which would necessitate either laparotomy or laparoscopy (ie surgical procedure to enter the abdomen) to remove it.

It is also important to check that there is nothing else apart from two testicles within the scrotum, as rarely a horse may have a hernia, in which case they should be castrated at the practice.

What is the procedure for castrating?

Regardless of whether a colt is castrated standing or under general anaesthesia; at home or in an operating theatre; the basic surgical procedure is identical. Both testicles are removed via a surgical incision into the scrotum – either one incision through which both testicles are removed, or two incisions, one for each testicle. The blood vessels and other network of tubes running from the testicle into the abdomen must be crushed and cut at the time of removal of the testicle.

There are two different techniques to castrate a colt under general anaesthesia. Either the ‘open’ technique, where the scrotum and vaginal tunic containing the 2 testicle are incised and then left open for drainage; or the ‘closed’ technique where the tissue layers are sutured once the testicles are removed, in order to reduce the risk of herniation. The closed technique takes longer and requires the cleaner environment of an operating theatre, therefore incurring a higher cost; however it has a lower risk of associated complications in older or very large stallions. When horses are castrated standing, under sedation, the open technique is used.

Can castration happen on my premises?

Colts can either be castrated here at Severn Edge Equine Vets, or at the owner’s premises providing they are suitable. The advantage to castrating a colt at home is that it removes the requirement for transportation. Someone experienced in handling horses will be needed, and preferably one who does not mind the sight of blood! The vet will also require a source of warm, clean water.

A flat grass field would be preferable to a stable when castrating a colt, in case we need to anaethasise which requires the colt to lie on the ground during the operation. Stables are often too small to anaesthetise a horse safely, and there is the increased risk of a horse hurting himself on any protuberances on the stable wall, during either induction of, or recovery from, anaesthesia.

The majority of castrations are performed under heavy sedation, using a local anaesthetic, however, this is dependent onthe horse being of suitable size and temperament. In this instance the ideal location to castrate the colt would be in a large well lit stable or barn. It is always best to discuss the facilities you have available with us to see if they are suitable, before booking the appointment for
the castration itself.

What post-operative care is required?

The exact details of post-operative care will vary on a case by case basis; however they will focus on cleanliness, close observation and exercise. Young animals can be turned out in a small paddock soon after surgery. Exercise will encourage drainage and minimise swelling at the surgical site. If a colt will not exercise sufficiently solo, enforced exercise may be required, with in-hand walking or lunging.

The colt may be prescribed a short course of antibiotics and painkillers following surgery, and the vet will ensure that the colt is protected against tetanus. If your colt has not already received the
primary course of vaccinations, anti-toxin should be given at the time of surgery, thereby providing immediate cover. The surgical site will need to be inspected on a daily basis for rapid
detection of any possible complications.

If there are no post-operative complications the incisions should be completely healed within two weeks. However, the colt should not be turned out with mares for at least two months following castration, in order to ensure that they are no longer fertile and they have lost the hormonal influence leading to ‘stallion-like’ behaviour.

What are the potential complications and risks?

Castration is generally regarded as being a routine procedure, and in the vast majority of cases it is both straightforward and uncomplicated. However, it should not be forgotten that it is an invasive surgery and statistics show that in approximately 1 in 5 cases, complications can occur.

An anaesthetic in any healthy horse carries with it an element of risk, although every attempt is made to minimise this risk. We will be able to advise what is best in your case. Bleeding is a potential post-operative complication. A small amount of blood dripping from the wound in the first twenty-four hours after castration is normal, but if it exceeds a fast drip, ring us immediately.


A potentially more serious complication can arise, if anything is seen to be hanging down from the surgical incision. This may just be a small piece ofthe vaginal tunic–the fibrous sac within which the testicle sits, in which case it can either be left alone to dry or trimmed off, depending on how much is protruding. In more serious cases it may be a piece of intestine that can prolapse from the castration site. This is a serious emergency and will require immediate veterinary attention.