A male horse is often gelded to make him better-behaved and easier to control. Gelding can also remove lower-quality animals from the gene pool. Ideally, horse breeders choose to leave only their best animals as stallions; lesser specimens are gelded, to improve the overall quality of the breed.
https://en.wikipedia.org/wiki/Gelding
Gender Differences: Training Geldings. Years ago, I had a client with a two-year-old Arabian colt that she wanted to keep as a breeding stallion. The colt was argumentative and constantly challenged anyone handling him. I got along with him fine but he was more horse than she could handle.
http://www.meredithmanor.edu/features/articles/drm/training_geldings.asp
Q. Do mares have behaviors that are specific to them and different from geldings? A. The timing of this question is very interesting considering The Horse just published the results of a poll on preferred sex of horses! I thought the selected comments pointed to some common themes.
http://www.thehorse.com/articles/35467/differences-between-mares-and-geldings
Gelding horses is generally approved of as a way to allow more horses to live comfortably and safely in proximity to humans and other horses, and as an ethical means of population control, even within the animal rights community.
https://en.wikipedia.org/wiki/Gelding
Owners of male horses, both geldings and stallions, need to occasionally check the horse's sheath, the pocket of skin that protects the penis of the horse when it is not in use for urination (or, in the case of stallions, breeding).
https://en.wikipedia.org/wiki/Gelding
A gelding is a castrated horse or other equine, such as a donkey or a mule. Castration, as well as the elimination of hormonally driven behavior associated with a stallion, allows a male horse to be calmer and better-behaved, making the animal quieter, gentler and potentially more suitable as an everyday working animal.
https://en.wikipedia.org/wiki/Gelding
Indeed, probably the biggest differences in behavior between mares and gelding are sexual behaviors. Mares are likely to show some signs of estrus, or heat, over the breeding season.
http://www.thehorse.com/articles/35467/differences-between-mares-and-geldings
A gelding might be more likely than mares to have tidier elimination practices if he happens to be one who marks or makes stud piles. A gelding that shows stallion sexual behavior is still not necessarily the dominant individual in the group, however (see our recent question on alpha horses). And one can't say that it is more typical of a gelding than a mare to be the dominant one in a group, or vice versa.
http://www.thehorse.com/articles/35467/differences-between-mares-and-geldings
It’s not as simple as “Boy and Girl” in the horse world…. A male horse is born as a Colt. When he’s three years old he’s called a Stallion even though he may be able to breed much sooner. If he is gelded (has his testicals surgically removed in an operation called castration) he’s known as a Gelding and is unable to breed. Sometimes a castration isn’t successful in removing every trace of the testicals (it’s a lot more difficult if the testicals are undescended) and he may become a rigg.
https://www.mareandfoal.org/blog/2011/04/13/what-are-colts-and-stallions/
Now when a colt is gelded, physiologically he does not go from being a stallion to a gelding overnight. The day after castration, he still has just about as many hormones circulating in his system as he did the day before.
http://www.meredithmanor.edu/features/articles/drm/training_geldings.asp
what is a gelding
A gelding is a castrated horse or other equine, such as a donkey or a mule.