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Castration in horses: Methods and potential complications

Tony Kaye BVSc MRCVS, St David’s Equine Practice

As autumn approaches, clients with male foals may face choices about whether to castrate them.  This article describes the choice of methods available to you and aims to give you more information to make the right choice for your foal or yearling.

Castration is defined as removal of the testicles and their associated structures.

The testicles are contained in two layers of the thin tissue that lines the abdominal cavity called the “vaginal tunic”. The testicles, their vaginal tunic covering and an attached muscle (called the cremaster muscle) lie inside the skin pouch of the scrotum.

Castration can be carried out by two main methods, open castration or closed castration.

Open castration is usually considered to be a clean rather than a sterile procedure because it is carried out in non-sterile conditions such as the stable or a field. The surgeon incises through the skin, subcutaneous tissue and the two layers of vaginal tunic to access the testicle. Because the vaginal tunic is continuous with the tissue lining the abdomen, this effectively opens a communication between the abdomen and the outside world, which increases risk of infection getting into the abdomen (peritonitis) or abdominal contents protruding from the surgical wound. The testicle is freed from its attachments to the scrotum and the spermatic cord (which contains the blood vessels and nerves supplying the testicle) is simultaneously cut and crushed by an instrument called an emasculator. Normally, the crushing action of the emasculator is relied upon to prevent bleeding after the castration from the spermatic artery and vein, rather than a stitch being applied. The wound is left open to drain and heal over time rather than being sutured.

We normally advise complete turnout after an open castration to encourage drainage from the wound and help to minimise the risk of infection. We also advise against stabling as fragments of bedding can get into the open wound and predispose to infection. Even the cleanest stable is usually less hygienic than the conditions in a field.

Open castration has several potential complications which include:

-Uncontrolled bleeding from the spermatic vessels.

-Infection (which gains entry through the open wound).

-Rarely, but most seriously, tissue or even gut from the abdomen protruding through the wound to the outside or infection gaining entry to the abdomen (peritonitis).

Certain environmental conditions can make complications after open castration much more likely, and because of this we may ask to delay your horse’s open castration if the conditions are not ideal. Conditions we try to avoid are:

-Wet or muddy conditions (which increase the likelihood of infection after surgery).

-Times of the year when flies are more active (as they are attracted to feeding off tissue fluids from an open wound and can cause either infection or maggot infestation).

-Below freezing temperatures (which can cause frostbite on the unhealed edges of the wound).

Closed castration is a sterile surgical procedure. Although no surgical procedure is risk free, closed castration dramatically reduces the risks that are associated with open castration and so clinically it is much preferred. The surgeon incises the skin, but not the vaginal tunic covering the testicle (so the risk of infection entering the abdomen, or abdominal contents escaping are much reduced) and the blood vessels supplying the testicle are ligated or stitched (so the risk of bleeding from these is much reduced). The skin incision in the scrotum is usually sutured (so the risk of post-operative infection is much reduced and healing is accelerated compared to open castration). Closed castration is normally carried out under general anesthetic.

Many of the complications of open castration noted above are increased in likelihood and severity in older horses, mainly because the testicles in older horses are larger and have a greatly increased blood supply.  This means that there is more risk of bleeding and there is a larger wound left behind which takes longer to heal and has more risk of becoming infected.  Because of this we feel that in older horses, carrying out an open castration represents a significant risk to the horse.  For this reason we recommend that horses over 2 years of age are castrated by the closed method.

St David’s Equine Practice provide the equine veterinary services for Molecare Veterinary Services.