"Gelding" refers to castrated equines like horses, donkeys or mules. When it comes to horses, castration makes the horse more manageable. Since hormonally driven stallions are more difficult to control, they may be castrated to induce behavioral change. To "geld" means to neuter or curb something. A horse that undergoes the process, hence, is called a gelding. In horse racing, some horses can be gelded if they are easily distracted by nearby animals, or is difficult to control. However, gelding makes winning horses ineligible for breeding- thereby often bringing down their market value. In that case, the value of the stallion that sired the gelding goes up.