Anabolic Steroids or Confidence?

Q: In reading the article by Dr. McDonnell about the effects of anabolic steroids on geldings and their behavior, I wondered how long the effects last after the steroids are given to the horse. I have a 3-year-old off-the-track Thoroughbred at home recovering from illness, and he is not the same sweet gelding I sent out for training. Even something as simple as leading causes him to go straight up in the air for no apparent reason, and he is finally learning that he cannot bite like a barracuda.

He was very docile before, and now he is aggressive over the fence with the mares and the other gelding.

I would just like to know how much of it is caused by the steroids and how much is newfound self-confidence, as it will make a difference in whether I wait it out or deal with it now.

Ginny, via e-mail


A: In work we did years ago studying the behavior and reproductive function of mares treated with two of the most common anabolic steroids used in horses, we found observable stallionlike behavior persisted in some mares for as long as three to six months after treatment had stopped.

In most cases, the measurable blood levels of the androgens that we were able to assess back then had diminished within a couple of weeks after treatment had stopped.

So if your gelding received anabolic steroids as a part of his treatment for his illness or while on the track, then the coltlike biting and the tendency to be light on his front feet are most likely attributable to the steroids, rather than the result of newfound confidence from simply recovering from the illness.

About the Author

Sue McDonnell, PhD, Certified AAB

Sue M. McDonnell, PhD, is a certified applied animal behaviorist and the founding head of the equine behavior program at the University of Pennsylvania's School of Veterinary Medicine. She is also the author of numerous books and articles about horse behavior and management.

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