Geldings & Low Testosterone Levels

A gelding is a male horse that has his testicles removed. This makes the horse much easier to work with and prevents unwanted foals. Because the testicles are the primary source of testosterone, it is normal for geldings to have much lower testosterone levels than intact colts or stallions. But when the testosterone level drops can differ from horse to horse.

  1. Time Frame

    • Male horses can be gelded at any point in their lives, even as young as three weeks old, according to "Horse Owner's Veterinary Handbook." But many horse breeders prefer to wait until the colt is at least a yearling. The testosterone is thought to help make a bigger, more beautiful horse with a thicker, more crested neck.

    Significance

    • The older a horse is before gelding, the more testosterone will be in his blood and the longer it will take for him to begin acting calmer after castration. If a stallion is four or more years old, the testosterone level will not drop for up to one year after the procedure, according to "Horse Owner's Veterinary Handbook." Any older stallion might be so set in his ways that even gelding and a drop in testosterone levels will not change his behavior, according to Brenda Forsythe Sappington, M.S., Ph.D.

    Problem

    • Some male horses are sold as geldings but are actually stallions with undescended testicles. Also called cryptorchid horses, they are infertile but can still act like a stallion. Testing for testosterone levels in the horse's blood does not help because the testosterone level of a cryptorchid stallion will be the same as a gelding, according to Patrick M. McCue, DVM, Ph.D. of the Diplomate American College of Theriogenologists.

    Misconception

    • Traditionally, geldings that still acted like stallions were called "proud cut." It was thought that the vet performing the operation had mistakenly left some part of the testicle inside the horse, such as the epididymis (located next to the testicle and used to store sperm cells). This leftover part was thought to still make testosterone. However, this is impossible, according to McCue.

    Fun Fact

    • Geldings can get erections. Testosterone levels do not affect the ability to get erections, blood circulation does. Stallions that have been gelded after a breeding career might still be able to mount mares although they are sterile, according to horse trainer and author Julie Goodnight.