A gelding is a castrated animal — in English, the term specifically refers to a castrated male horse or other equine such as a donkey or a mule. As a verb, it also refers to the castration procedure itself. The word comes from the Old Norse geldr ("barren"). Castration, and 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.
To allow only the finest animals to breed on, while preserving adequate genetic diversity, it is recommended that only a small percentage of all male horses should remain stallions. Some sources place the percentage of stallions considered unacceptable breeding stock at about 90%, while others would be more radical and state that only 0.5% should be bred. In wild herds, the 10% ratio is largely maintained, though via a different mechanism, as a single stallion usually protects and breeds a herd of up to 10 or 12 mares, though may permit a less dominant junior stallion to live at the fringes of the herd. There are more males than just herd stallions, but unattached male horses group together for protection in small all-male "bachelor herds," where, in the absence of mares, they tend to behave much like geldings.
Geldings are preferred over stallions for working purposes because they are calmer, easier to handle, and more tractable. Geldings are therefore a favorite for many equestrians, especially amateurs. In many horse 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 a 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 that 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, which is often retired to stud immediately following a short but successful track career.
Sometimes a stallion used for breeding is castrated later in life, possibly due to sterility, or because the offspring of the stallion are not up to expectations, or simply because the horse is not used much for breeding, due to shifting fashion in pedigree or "look." Castration often allows the retired stallion to live a more social and comfortable existence close to or with a herd of other horses.
Under British National Hunt racing (i.e. Steeplechase) rules, to minimize the health and safety risk for horses, riders, and spectators, nearly all participating horses are geldings. 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.
Hesitation to geld a horse may occur out of concern that a gelding, once past its athletic prime, will be of no economic value for anything but the horsemeat market; whereas a stallion can be used for breeding purposes even if injured or too old to be athletically competitive. However, the consideration of whether a male horse is of a quality suitable for breeding stock must not be overlooked. Furthermore, though some nations have an active horsemeat industry, many geldings are actually retired to pasture and allowed to live out a normal lifespan.
Some cultures historically did not and still seldom geld male horses, most notably the Arabs. These people usually used mares for everyday work and for war. In these cultures, most stallions are still not used for breeding, only those of the best quality. When used as ordinary riding animals, they are kept only with or near other male horses in a "bachelor" setting, which tends to produce calmer, less stallion-like behavior. Culled males are often sold away to other cultures, some of which lack the cultural taboos against gelding horses, while others simply slaughter them for horsemeat. Gelding was not practiced by the ancient Israelites and was forbidden in the Bible.
Gelding horses is generally approved of as a way to allow more horses to live comfortably and safely in close proximity to humans and other horses, and as an ethical means of population control, even within the animal rights community. However, some individuals are concerned that the process may cause pain for the animal or somehow lessen their vitality or spirit. While modern surgical procedures cause far less discomfort to the animal than more primitive methods, there is minor postoperative discomfort when the animal is in recovery. Gelding a horse does not reduce its athletic potential or strength, but the reduced aggressiveness of the animal may be viewed as a minus in some competitive endeavors.
Many older stallions, no longer used at stud due to age or sterility, can benefit from being gelded. Modern veterinary techniques make gelding of 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.
Some horses object to sheath cleaning and require sedation, others will tolerate it if the groom is careful and patient, though light sedation may help the horse "drop" for easier cleaning. Ideally, the horse will be desensitized by careful training to tolerate the procedure. To begin, a gentle stream of warm water is run into the sheath from a hose or a large, needleless syringe. This will loosen and soften some of the material and make it easier to remove. The process requires either that the horse "drop" its penis or that the groom reach up inside of the sheath to pull the penis gently from the sheath by the glans (head) in order to apply cleaner and carefully clean the entire region. The "bean" is often found in the urethral diverticulum, a pocket adjacent to the opening of the urethra, so that area must also be checked. While a veterinarian can clean a sheath, it is not a medical procedure and can be done by any person who learns the proper method.
For standing castration, the colt or stallion is sedated, typically with detomidine with or without butorphanol, and often physically restrained. Local anaesthetic is injected into the parenchyma of both testes. An incision is made through the scrotum and the testes are removed, then the spermatic cord is crushed, most commonly with either ligatures or emasculators, or both. The emasculators are applied for 2–3 minutes, then removed, and a careful check is made for signs of haemorrhage. Assuming that bleeding is at a minimum, the other side is castrated in the same manner. Most veterinarians will remove the testis that is held most "tightly" (or close to the body) by the cremaster muscle first, so as to minimise the risk of the horse withdrawing it to the point where it is inaccessible. The horse, now a gelding, is allowed to recover.
Standing castration can be performed in more complicated cases. Some authorities have described a technique for the removal of abdominally retained testes from cryptorchid animals, but most surgeons still advocate a recumbent technique, as described below. The other drawback to standing castration is the risk that, even with sedation and restraint, the horse may object to the procedure and kick or otherwise injure the individual performing the operation.
Putting a horse under general anaesthesia for castration is preferred by some veterinarians because "surgical exposure is improved and it carries less (overall) risk for surgeon and patient." For simple castration of normal animals, the advantages to recumbent castration are that the horse is prone, better asepsis (sterile environment) can be maintained, and better haemostasis (control of bleeding). In addition, there is significantly less risk of the surgeon or assistants being kicked. In addition, in a more complex situation such as castration of cryptorchid animals, the inguinal canal is more easily accessed. There are several different techniques (such as "open", "closed", and "semi-closed") that may be employed, but the basic surgery is similar. However, general anaesthesia is not without risks, including post-anaesthetic myopathy (muscle damage) and neuropathy (nerve damage), respiratory dysfunction (V/Q mismatch), and cardiac depression. These complications occur with sufficient frequency that castration has a relatively high overall mortality rate. To minimize these concerns, the British Equine Veterinary Association guidelines recommend two veterinary surgeons should be present when an equine general anaesthetic is being performed.