Ask The Vet: Castrations

Answered by,  Jennifer Reda, DVM, Steele Equine Veterinary Services, Zolfo Springs, FL and Stephanie Regan, DVMCourtesy 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: Can you castrate a 12-month-old colt if the testes have not dropped yet? What is the best age to castrate for maximum physical development? 

Answer: The condition you are describing in your colt where one or both testes fail to descend into the scrotum is called cryptorchidism.  Other terms for this are that the colt is a “crypt” or a “rig” or a “ridgeling”. While the colt is still in utero, the testicles should descend through the abdominal cavity and inguinal canals into the scrotum. This usually occurs in the last 30 days of gestation or first 10 days after birth. If your colt still has both testicles undescended at 12 months, there is only a small chance that they will descend at all. So where are the testicles? They could still be all the way up in the abdomen, or they could be located in the inguinal region. If in the inguinal region, they are often palpable. If the testicle is in the abdominal region, it will not be palpable but may possibly be visualized on ultrasound.

Moving on to your next question of if your colt can be castrated, the answer is yes. However, since his testicles are not descended, this will be a specialized castration performed by an experienced veterinarian. The best way to castrate a bilateral cryptorchid stallion is through laparoscopic surgery. This is done under general anesthesia. The colt is placed on his back, and a small incision is made, through which the device called the laparoscope is inserted. The laparoscope contains a camera where the testicle can actually be visualized and then removed. This surgery is minimally invasive, meaning the incisions used for this are small and the surgery is very precise. If for some chance there is any problem with visualization of the testicle via the laparoscope or there are complications, the horse is already in an appropriate, sterile surgical setting with proper anesthetic equipment and monitoring to convert the surgery into an open approach into the abdomen.

Alternatively, skilled field veterinarians will also attempt to do cryptorchid surgeries in the field. This is possible for inguinal testicles, but usually for testicles in the abdomen practitioners prefer to do these surgeries in a sterile environment. Sometimes it can be hard to determine where the testicle is until the horse is already anesthetized, and you run the risk of not being able to finish the surgery if the testicle is retracted into the abdomen or just simply isn’t where it was thought to be originally. Even inguinal testicles (high flankers) should be castrated with an assistant to run and monitor anesthesia as these can be longer, more tedious procedures than a simple castration. Also, multiple attempts at removing a cryptorchid testicle can make surgery in the future at a referral clinic more difficult due to scar tissue, and often the history is lost along the way of whether the testicle was actually removed or not.

To answer your last question about the best age to castrate for physical development, the most common time we like to castrate is between 6 and 12 months old. That being said, we have castrated very young and very old stallions. However, there are some reasons behind the 6-12 month old recommendation. First, the testicles have adequate testicular development after about 3 months old, which makes them easier to find and sever. Second, the chances of excessive bleeding are reduced when you geld at a younger age as the testicles are not quite as large as waiting until, say, 3 years old. Younger horses often tolerate anesthesia better, recover more quickly, and heal faster than older horses. The size of the opening to the abdomen that the spermatic cord travels through can differ with maturity, meaning the risk of abdominal content coming through that opening can be higher with an open approach in the field. Finally, stallions that are castrated later in life tend to retain more of their learned stallion behaviors even after they have been gelded. For all of these above reasons, we would recommend castrating your colt now, ideally laparoscopically. Best of luck to you and your soon-to-be gelding!