Breeding

Castration: Part 1

It’s one tool to decrease the number of unwanted horses.

It is a fact that unwanted horses, genetic diseases, a declining sales environment, poor production outcomes and horses that do not meet our expectations are often the result of poor breeding decisions.

Those decisions usually start with deciding whether or not a young foal has the potential to be successful in the show ring or on the track and eventually in the broodmare band or standing at stud. Because a stallion has the potential to sire hundreds of foals, the decision to geld a colt is especially important.

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My father was in the commercial cattle business and he always said, “It takes a good bull calf to make a good steer.” Following that good advice, we always picked out the best bull calf to castrate and show in our 4-H steer class at the local fair. I have the same opinion on horses. Generally, less than 1 percent of each year’s colt crop is good enough to become a breeding stallion.

Why Castrate?

Owners tend to castrate colts for two reasons. The first we’ve already discussed, and that is to keep only the very best to perpetuate the breed. The second is that stallions are testosterone-driven and can be aggressive and potentially dangerous to other horses and people. The AQHA Handbook lists several undesirable traits, including parrot mouth, cryptorchidism, homozygous for HYPP and excessive white with underlying pink skin. Other than being homozygous for HYPP, horses possessing one or more of these conditions are not prevented from being used as breeding stock or participating in AQHA events. I know I possess a veterinarian’s bias, but if we’re going to continue to improve the breed and minimize the number of horses that fail to meet our expectations, we should geld colts that possess any of these undesirable traits. Of course, that decision is made more difficult if the colt is an extremely good athlete or has perfect conformation. I believe that if a colt has a marginal pedigree, possesses undesirable traits or does not possess exceptional breeding potential, he should be gelded early in life, just prior to or following weaning.

Some of the advantages of early castration are that the colt never develops stallion-like behavior or secondary sex characteristics. In addition, colts castrated at 4-6 months of age generally experience few post-castration complications such as weight loss, excessive scrotal swelling or infection. I like to castrate colts two or three weeks prior to weaning and then turn them back with their dams where they can get plenty of exercise and a little TLC. I’ve gelded colts as young as 30-45 days of age and they do fine. Colts gelded prior to puberty often grow taller than if they were left intact until after puberty. The testosterone surge at puberty (18-24 months) triggers closure of the growth (epiphyseal) plates in the long bones of the legs and the horse stops growing taller. The theory is that colts gelded at less that one year of age do not experience the pubertal testosterone surge that allows more long-bone growth and extra height. Stay tuned next week for the second half of this story.

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