Ask the Vet: Castration

Answered by Jennifer Reda, DVM and Stephanie Regan, DVM Courtesy of AAEP

Question: I have always gelded my colts at about 5 months of age, before they are weaned, so the mare is with them for comfort and to keep them moving.

Is there any science to indicate that this early castration might be detrimental to their long-term health or performance prospects?

Answer: Great question! Many veterinarians and horse owners castrate at around the time you described, 5-6 months, as long as the testicles are fully developed and fully descended. At this age, the testicles are smaller and easier to remove, and there is also less of a risk of severe bleeding post-operatively. Most weanlings we have done recover very quickly and don’t miss a beat going back to their normal lives.

Thus far, we have not found any scientific evidence or peer-reviewed research paper that castration as a weanling has any negative effects on the horse’s long-term health. In fact, there are large retrospective studies that do not correlate age with increased risk of complications. Stallions can develop some undesirable medical conditions that geldings do not, such as testicular torsion or scrotal hernias. In terms of performance, some of this depends on discipline.

Disciplines such as halter horses often desire more heavily built, muscular horses. This horse is not able to “perform” any better in terms of any athletic capacity, but simply the breed standards on which they are judged may favor the musculature of stallions. Geldings are often high achievers in both the English and Western performance horse worlds, preferred for many hunter and jumper disciplines. We do know scientifically that geldings grow taller than stallions—the growth plates in their legs remain open longer when they are castrated early, thus allowing them to grow taller. Certainly, many people like to keep their horses intact for potential breeding purposes if they show aptitude in their sport.

Many owners wait until the colt becomes a management problem to geld them, which is often between 2 and 3 years old. These horses will likely retain some of their stud horse behavior even after gelding, especially if they have been allowed to breed or even mount other mares. In conclusion, your castration protocol is perfectly fine.

Question: What is the most common method for castration? What is the youngest age you would recommend castrating? My colt is 6-months-old. I just brought him home so wanted to give him a chance to adjust to his new life before castration. Is it ok to castrate in the cold winter if your horse is turned out all day?

Answer: There are several different methods for routine castrations where both testicles are descended. We would say that in the field most practitioners perform castrations under field anesthesia, using intravenous drugs that will lay the patient down for approximately 20 minutes.

The other option would be to do standing castrations, which are performed by many veterinarians at racetracks and training centers, although for a weanling this is not the preferred option. For a standing castration, the horse is sedated heavily but remains standing, and the testicles are removed while the horse is standing.

Yet another option is for horses to be sent to a referral clinic where the castration can be performed with primary closure, meaning the incision is closed with suture and the scrotum is not left open. Any of these methods can be effective and this depends on the veterinarian’s preference, breed of horse, presence of complicating factors, training schedule, etc.

Most veterinarians will castrate using emasculators. The scrotum is opened and the testicles are extracted, and then the spermatic cord is clamped and then cut for each testicle. There is an alternate instrument for castrations called the Henderson which attaches to a power drill, however in our combined experience not many veterinarians are using this instrument. If in the hospital setting, the surgeons may use an instrument called a LigaSure, which is a vessel sealing device that uses energy and pressure to seal vessels up to 7mm in diameter and has been showed to reduce intraoperative blood loss compared to suture ligations.

In terms of age of castration, the timing is usually a product of managerial convenience; i.e. when masculine behavior is intolerable to the owners or it is determined that breeding is not desired in the future. We typically recommend between 6 and 12 months old. That would mean your colt could be castrated at any time now, as long as he has both testicles descended and fully developed.

Allowing your colt to adjust to his new home would be fine as you are still well within the 6-12 month window, and it is certainly possible to castrate later in life as well. In regards to the winter, yes your horse can absolutely be castrated in the winter, as long as your personal veterinarian is game. In fact, many practitioners prefer winter over summer, as they don’t have to deal with the humidity and the insects.

If you had any concern as to weather or turnout conditions, primary closure is also an option as there would be no open incision. However, this would need to be performed at a referral facility.

And finally, turnout is ideal for horses that have just been castrated in the field. In fact, the more walking around and even actual exercise post-castration such as lunging, the better because it reduces swelling and inflammation. If primary closure is performed, horses are usually stall rested and hand walked for two weeks until the incision is healed, and then can return to full exercise.