Regumate to Control Stud Behavior?

Q: My yearling stallion has begun his show career in longe line classes. He is beginning to lose concentration and act "studdy" at shows. It was suggested that I put him on Regumate to help control this behavior (as an alternative to gelding). What are the pros and cons?     Jennifer

A: Altrenogest (brand name Regumate) is a synthetic progestin that mimics certain actions of progesterone in horses. The concern for its effect on stallion behavior is probably based on reports that behavior can be modified in some geldings that act aggressive and stallion-like. It is highly unlikely that a similar response can be expected in an intact stallion because testicular production of testosterone and estrogens should completely override the progesterone effect. In other words, it is extremely doubtful that it will work on a stallion.

About the Author

A.C. Asbury, DVM

A. C. (Woody) Asbury received his DVM from Michigan State University in 1956, then spent 21 years in California in breeding farm practice and at UC Davis. He joined the faculty at the University of Florida in 1977 and was involved in teaching, research, and administration until 1996. An Emeritus Professor at Florida, he lives in Kentucky, where he and his wife are developing a small farm.

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