Equine Reproduction

Question: I have a nearly 4-year-old APHA stud colt, that seems to have hit a rut growing and developing muscle. He was underfed and not properly cared for as a foal/yearling and now I can't seem to get him going again. Neither of his testicles have descended and even with regular workouts he isn't gaining muscle mass and is on a good feed. My question is that some pros in the industry have told me to look into trying steroids on him short-term to jump start his system. Would this be a good idea? If so, what type should I be looking at? I have been in the industry for over 14 years and have never encountered a problem like this.

Answer:  If your horse is that old, he will not grow in height. You can verify this by taking radiographs of the growth plates in his carpi (knees). They will most likely be closed, indicating no more vertical growth is possible. Likewise, his testicles should be descended at birth and if you really want to be generous, many people will wait until the horses are 16 to 18 months old. After that point, if the testicles are not in the scrotum, he is a bilateral cryptorchid and should be castrated as this is a very heritable genetic defect. Anabolic steroids are used to increase muscle mass and appetite just as in people. You need to check with your show industry rules as these are becoming more tightly restricted. There are health detriments, just like in people. The use of anabolic steroids in this animal would be the same question as a human athlete. There are serious side effects, a lot of ethical concerns, but there are tremendous benefits as well.

Question: Could a gelding that was cut when he was 4-years-old (now 8-years-old) possess stallion instincts? My horse has really good breeding (Thoroughbred) so why geld? He still acts like a stallion in that he herds my mare, nips/bites her and he gets jealous when she gets the attention from my husband, almost as if he is competing for her. What do you think?

Answer: It sounds like you are asking two different questions. The first question is easy. Some stallions have retained testicular tissue and there are blood tests that can identify this...most commonly Testosterone and Estrone Sulfate levels are drawn before and after HCG administration. This is called an HCG Stim Test. Many geldings retain stallion-like activity(maybe over 60 percent) because of learned behavior (having nothing to do with hormones).
Your second question you ask why should you geld/castrate a horse that has good breeding. There is a nationwide problem with the unwanted horse, the values of horses are 40-60 percent of what they were worth as recently as three years ago (feeding them and training them is still just as expensive), and no matter how many manners a horse has, stallions always need to be treated with caution and respect because, like every horse, they have the potential to be dangerous. You need to have a plan if you want to keep a horse intact. No one should casually leave a horse a stallion unless they are set up for that situation.
The third sentence of your question implies that you are asking again about the gelded/castrated horse and it having some behavioral/herding issues. As I said in one of the above sentences, the large majority of horses that are castrated and act like stallions have misbehavior not hormonal problems. The way you start your diagnosis is to have an equine veterinarian do an HCG stim test and then if all the hormones indicate that the horse is completely castrated, you invest in advice from a trainer.

Question: I have a mare that will be 8-years-old in May. She has become a dominant mare over time and uses her feet to kick. She has hurt another horse, but not seriously. She has now been separated, and is currently by herself, but along side other horses in the pasture. I'm at a loss for understanding her behavior, which has become overly dominant and ultimately, too aggressive. I've wondered about her hormone level, or if something else is going on within her "female area". Have you had experience with this type of behavior?

Answer: It is very common for mares to have dominance or aggression issues. By all means, I would have her hormone levels checked. Many mares with hormone-secreting tumors can have aggression or even stallion-like behavior (mounting and herd dominance). The most common hormone-secreting tumors in the mare are granulosa-thecal cell tumors. There are many labs (I use Cornell University) that run "Granulosa Tumor Screens". They will look for inhibin primarily, but will also run levels of testosterone, progesterone and estradiol. Great question.
Reprinted with permission of the AAEP. To view entire article please visit www.aaep.org then click Horse Owners, Ask the Vet.

Reprinted with permission from AAEP. To view the entire article please visit www.aaep.org/ask_the_vet.php