Page "Gelding" Paragraph 4

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 he 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 performed 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, so long as appropriate analgesics are employed.

A few horse owners delay gelding a horse on the grounds that the testosterone gained from being allowed to reach sexual maturity will make him 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 ; the net effect is that castration has no effect on rate of growth ( although it may increase the amount of fat the horse carries ).