by Dr. Jim and Lynda McCall



The Problem:

Two years ago, I bought a three month old weanling stallion with hopes of making him into a show horse. Now don't think that I planned on keeping him a stallion. I was ready to have Buddy gelded as soon as possible. At nine months of age, Buddy was a gentle, willing colt with one descended testicle. Upon the advice of my vet, I agreed to have him castrated. Personally I wanted to wait until both testicle were present but he indicated that if the colt hadn't dropped by now, he probably wasn't going to.

My horse continued to grow and mature nicely until about twenty months of age when he began displaying a very dominant nature. He began herding horse and mating with receptive mares - in other words, he began showing stallion behavior.

My vet did a testosterone level test which indicated that Buddy was producing the male hormone at stallion levels. Three unsuccessful surgery's later, my horse is still behaving like a stallion. Any advice or suggestions would be greatly appreciated.
Tricia C., Louisiana

The Answer:

We think that it is evident that Buddy has a physiological problem that is influencing his behavior. Many behaviorists today believe that the root of much of behavior is dictated by the physiological make-up of the individual; Buddy's problem seems to highlight that theory. The search for a possible solution to Buddy's behavior begins with an understanding of the development of a sexually active stallion.

Embryonically, tissue destined to ultimately become either the testes or the ovaries is located near the spine. During the fetal development of the stallion, the tissue develops into testicles, beginning their descent through the body during the last trimester of pregnancy. (In the mare, the same tissue becomes ovaries and stays inside the body cavity).

To reach the scrotum, the two testes - one from the right side of the body; the other from the left - enter their respective canals (inguinal canals) which provides an exit route out of the body cavity. At the entrance to these canals is a structure known as the inguinal ring. This ring is under a biological timetable for closure. The testes must pass through the ring before closure or else they become trapped in the body cavity. Although there is some genetic variation for this biological clock, closure is normally estimated to occur at about 60 days of age.

This does not mean that a colt that has not dropped by 60 days of age will be a cryptorchid (a term used to denote a male horse with either one or two testicles housed inside the body cavity). The testicles (either one or both) can continued to descend through the canal until as late as two to three years of age.

But, obviously, this does not apply to Buddy. Three additional surgical attempts to locate the "lost" testicle have surely eliminated the possibility that the testis is trapped in the inguinal canal. Our recommendation would be take the horse to a equine veterinarian with considerable experience in dealing with this problem.

At this point, Buddy's history compounds his problem in several ways. First, the prior surgeries have produced scar tissue in which the missing testicle might be hidden. And the surgical procedures themselves have also changed the appearance of the internal structures. This demands an equine surgeon experienced in operating on horses that have previously been operated on.

Secondly, with the removal of the one descended testes, the marker is gone. This means that there is no way of knowing whether the "lost" testes is the one that was supposed to descend from the right or left side of the horse. According to Dr. Tex Taylor at Texas A & M Vet School, the rule of thumb is "Get the missing one first!" Leave the visible testicle so that repeated attempts to look for the missing testis will be on the appropriate side of his body.

Dr. Taylor also indicated that many missing testicles can be located by rectal palpation prior to surgery. But the success of this procedure, again, demands an veterinarian with experience in this area. Palpation is definitely an acquired skill and one that demands continued practice to stay sharp. Not to mention the fact that most male horses are not receptive to being palpated (another cry for an experienced practitioner) or may, actually, be too small to palpate.

All these factors contribute to our original conclusion: Get Buddy to a specialist.

Now let's assume that Buddy's has had the successful removal of the missing testicle. Are your problems over? Probably not! Buddy has learned how to act like a stallion. The removal of the testicle will eliminate the production of testosterone by the sex gland but testosterone is also produced in smaller amount by the adrenal cortex. Usually this amount is too small to produce full blown stallion behavior in the castrated male, but for the older horse that has been sexually active, it may be enough for him to "want" to continue some of his behavior.

Whenever we castrate an older male, we try and make it a practice to turn him out with a group of non-receptive mares for resocialization. For the once fertile male, we wait approximately six to eight weeks to allow the elimination of any sperm cells which might be lurching in his reproductive tract.

Buddy does not have this problem. Although a testis trapped inside the body cavity produces testosterone, it is not capable of producing viable spermatozoa - thus the horse is sterile. He could be placed back into a herd situation as soon as significant healing of the surgery site has occurred.

After approximately thirty days of herd resocialization, it is time to extinguish any remaining stallion behaviors that may limit Buddy's usefulness as a show or pleasure horse. If Buddy's "recovery" proceeds normally, his aggressive levels should have waned and he should be much more receptive to dominance from his rider. If you lack confidence in pulling this off, it might be a good investment to send him off to a trainer for reschooling.

We hope there is a happy ending to this unfortunate situation.

Copyright © 1997.  Dr. Jim and Lynda McCall

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