Gelding Still Acting Like a Stallion

Q: My friend has a 14-year-old gelding who was gelded late (I'm not sure how late, but he did sire some foals) and is pastured with a 23-year-old mare. Last spring they were fine pastured together. This spring, however, she started her heat and he bit her severely all along her lower crest and withers and chased her around to the point of soreness and exhaustion. The horses have now been separated. Will he settle down as spring progresses? Should we medicate him in any way? What do you suggest for managing these two "pasture buddies" again?


A: Your friend's situation offers a fairly common, but tough, challenge. Glad to hear they were able to separate them for the meantime. Separation was a good choice, and it might be the simplest and most effective strategy whenever the mare is in estrus.

A good percentage of geldings retain enough stallionlike behavior to be problematic when kept at pasture with mares. As might be the case with this gelding, some often seem tough on mares, causing even more wear and tear than an intact stallion might pose. These geldings tend to chase and herd relentlessly, and they mount and mount and mount. Since most appear slow to ejaculate, or might not ejaculate at all, they can appear to spend a lot more time pestering and trying than an intact stallion that would satiate and give it a break.

It is not easy to predict whether a gelding will "settle down" as spring progresses. He might get more animated about his interest until your mare stops cycling in the fall. It's curious why he was okay last spring. If this mare is cycling this spring at age 23, I would expect she was cycling last spring, too.

As far as medicating a gelding, there are some things people find useful for subduing residual sexual behavior in geldings during performance or show or other work where they take direction from humans. Treatment with a synthetic progesterone, such as Regu-Mate, at high doses, can subdue studdish behavior in some individuals in controlled situations, but it is unlikely to make much of a difference in an open pasture situation. If it is just this one mare pasture buddy, and for some reason it is not possible to separate them when she is in estrus, then it might be easier to suppress the estrus in the mare rather than to try to subdue the sexual interest of the gelding. That can be done with progesterone treatment or any number of methods. A veterinarian could evaluate this mare's reproductive tract and advise on the simplest and most effective method for suppressing estrus in this aged mare. Perhaps one of the simple and inexpensive intrauterine devices would work for this mare.

One last comment--your question seems to imply that maybe the residual stallionlike behavior in this gelding is greater because of castration after breeding experience. It's very interesting, but the degree of residual stallionlike behavior in a gelding is probably not as much determined by age or previous sexual experience as you might expect.

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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