Castration is a common surgical procedure performed by a vet. The purpose of a castration is to remove both of the testicles. The testicles are the source of sperm and testosterone, by removing them the horse’s behaviour is changed and he is unable to reproduce. While castrations may be performed in a sterile operating theatre, most of them are done in the field. Some vets may offer to perform the procedure standing with heavy sedation, however most prefer the horse to be fully anaesthetized and laid on the ground, either on their back or on their side.
Most owners will elect to castrate any male horse they do not wish to breed from. Castration eliminates the risk of the horse impregnating mares. This simplifies management on a property with multiple horses as stallions must be managed separately from mares if a foal is not wanted. Castrating a stallion also reduces or prevents some of the undesirable behaviour a stallion may exhibit such as aggression towards other horses or people. While a stallion may be castrated any time after 3 months of age, many people elect to have their horses castrated between 6 months to 2 years of age. Stallions may be castrated when they are older, and many certainly are, but older horses tend to have a slower recovery after the surgery than younger ones and a slightly increased risk of complications. If the procedure is performed in the field it is often preferable to castrate a horse in the spring or the fall as during the winter it may be muddy and during the summer there tend to be more flies to irritate the incisions after the surgery.
Prior to surgery, the stallion must be in good health. He should also be up to date with his tetanus vaccinations. If he is not vaccinated for tetanus, a tetanus antitoxin can be administered on the day which will protect him for the surgery however it is important to note that this is not a vaccine, it only offers temporary protection for a few weeks. In addition to being shorter acting, one tetanus antitoxin also costs more than a full course of vaccines. Well handled horses that are used to being haltered and led are easier to inject and often require fewer drugs, making the procedure faster and cheaper. Choosing a spot for the surgery is important, ideally the surgery should take place in a dry, flat, grassy paddock, free of potential hazards such as vehicles, ponds or trees. The weather is also important, the surgery cannot go ahead if it is raining or extremely windy.
Before the horse is castrated, the vet checks the horse over to make sure he is fit and healthy for anaesthetic and they make sure there are two testicles present. Occasionally one or both testicles may not descend into the scrotum, this condition is called cryptorchidism. If this is the case the castration cannot take place in the field as retrieving the retained testicle may involve abdominal surgery and this requires a sterile environment. While a retained testicle will likely not be fertile it will still produce testosterone and the horse will still act like a stallion and attempt to breed mares.
Once the vet has assessed the horse and determined that he can be castrated, the horse is then anaesthetized. The horse is positioned how the vet prefers and the surgical site is thoroughly cleaned. An incision is made over the testicle, the testicle is isolated, then a tool called an emasculator is used to crimp and cut the spermatic cord. Bleeding is prevented through the crimping action which seals off the blood vessels. At the end of the procedure the horse will be left with two incisions, these are left open to drain. Pain relief and antibiotics are usually prescribed.
For the first 24 hours, the horse should be kept confined to a small area so as to prevent him from running around and dislodging clots. After the first 24 hours, controlled exercise is very important. 10-15 minutes of hand walking or lunging per day for 2 weeks will help reduce swelling. The horse may be turned out in a small paddock provided it is not muddy but it should not be assumed that he will exercise himself, he may not feel like moving around and walking or lunging him ensures that he gets that exercise. Cold hosing was formerly recommended for swelling but this has been associated with an increased risk of infection and is no longer advised. The gelding should be isolated from mares for at least a month. Sperm will still be present in his reproductive tract for a couple of days after surgery and he could still breed a mare. It may take several weeks for the stallion behaviour to disappear as testosterone will remain in his system for a while after the surgery and older stallions sometimes never lose this behaviour.
Complications to watch out for after a castration has been performed include bleeding, swelling, infection and evisceration. A small amount of bleeding after the procedure is normal, however if the incision is bleeding so fast that you cannot count the drops or there’s a continuous stream, this is an emergency and a vet must be called to stop the bleeding. Post operative swelling is also normal and controlled exercise will help reduce it. However if the swelling becomes so large that it is interfering with the horses movement or doesn’t start to go down after 5 days, the vet should be contacted. Excessive post operative swelling, pain and lameness may also indicate infection, this requires veterinary attention. Evisceration is a rare but very serious complication. This is when a bit of intestine falls out through the incision. This is an emergency, the vet should be called immediately and the horse kept confined until the vet arrives. If you’re ever unsure, sending a photo of the problem to the vet can be an easy way to help determine if your horse needs to be seen.
by Alison Greaves
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