A gelding is a castrated male horse. The word comes from the Old Norse geldr ("barren").
A male horse is often gelded to make him more well-behaved and easier to control. Gelding also removes lower quality animals from the gene pool; breeders choose to leave only their best animals as stallions; lesser specimens are gelded, to improve the overall quality of the breed. To allow only the finest animals to breed on, while preserving adequate genetic diversity, it is recommended that about 10% of all male horses should remain stallions.
Geldings are preferred over stallions for working purposes because they are calmer and easier to handle. Geldings are therefore a favorite for many equestrians, especially amateurs. In many breed shows, due to the dangers inherent in handling stallions, requiring experienced handlers, youth exhibitors (and occasionally, women) are not permitted to show stallions in classes limited to just those riders.
Geldings are often preferred over mares, because some mares become temperamental when in heat. Also, the use of mares may be limited during the later months of pregnancy and while caring for the young foal.
In horse racing, castrating a stallion may be considered worthwhile if the animal is easily distracted by other horses, difficult to handle, or otherwise not running to his full potential due to behavioral issues. While this means the horse loses any breeding value, a successful track career can often be a boost to the value of the stallion who sired the gelding, and the horse himself may win substantial purse money on the track, as he is apt to race for many more years than would a stallion, who is often retired to stud immediately following a short but successful track career.
Under British National Hunt racing (i.e. Steeplechase) rules, nearly all participating horses are geldings to minimize the health and safety risk for horses, riders and spectators. On the other hand, in Europe, geldings are excluded from many of the most prestigious flat races including the Classics and the Prix de l'Arc de Triomphe.
A horse may be gelded at any age; however, if an owner knows that he or she intends to geld a particular foal, it is now considered best to geld the horse prior to becoming a yearling, and definitely before it reaches sexual maturity. While it was once recommended to wait until a young horse was well over a year old, even two, this was a holdover from the days when castration was perfomed without anesthesia and was thus far more stressful on the animal. Modern veterinary techniques can now accomplish castration with relatively little stress and minimal discomfort. A few horse owners delay gelding a horse on the grounds that the testosterone gained from being allowed to reach sexual maturity will make it larger. However, recent studies have shown that this is not so: any apparent muscle mass gained solely from the presence of hormones will be lost over time after the horse is gelded, and in the meantime, the energy spent developing muscle mass may actually take away from the energy a young horse might otherwise put into skeletal growth.
Many older stallions who are no longer used as stud due to age or sterility can benefit from being gelded. Modern veterinary techniques make gelding even a somewhat elderly stallion a fairly low-risk procedure, and the horse then has the benefit of being able to be turned out safely with other horses and allowed to live a less restricted and isolated life than was allowable for a stallion. (Wikipedia)
