Orchiectomy is the surgical removal of one or both testicles from a male animal. It’s one of the most commonly performed veterinary procedures in the world, applied across species from dogs and cats to horses, cattle, and pigs. You’ll more often hear it called “neutering” or “castration,” but orchiectomy is the precise medical term. The surgery eliminates the primary source of testosterone, which affects everything from reproductive ability to behavior, metabolism, and long-term disease risk.
How the Surgery Works
In dogs, the most common approach involves a pre-scrotal incision (made just in front of the scrotum), through which each testicle is pushed forward, exposed, and removed. The blood supply and spermatic cord are tied off with absorbable sutures before the testicle is detached. In cats, the procedure is similar but simpler due to their smaller anatomy, and the incision is typically made directly over the scrotum.
Veterinarians use two main techniques: open and closed. In an open orchiectomy, the surgeon cuts through the tissue layer surrounding the testicle (the vaginal tunic) to expose it directly. In a closed technique, that layer stays intact and is removed along with the testicle. The distinction matters because complication rates differ. One study comparing the two approaches in dogs found that 70% of dogs undergoing the open method experienced at least one complication event, compared to 46% with the closed method. Scrotal complications specifically occurred in 61% of open cases versus 33% of closed ones. Most of these complications are minor, like temporary swelling, but the closed technique generally carries fewer risks for routine procedures.
Why It’s Done: Health Benefits
The most straightforward benefit is eliminating the possibility of testicular cancer, which is among the most common tumors in intact older male dogs. Orchiectomy also dramatically reduces the risk of prostate enlargement, a condition that affects the majority of intact male dogs by middle age. Perianal tumors, which are testosterone-dependent growths near the rectum, become far less likely as well.
For cats, the health picture is somewhat different. Intact male cats are more prone to fighting-related injuries and the infections that follow, including abscesses and transmission of feline immunodeficiency virus. Removing the hormonal drive behind territorial aggression reduces these risks considerably.
Behavioral Changes After Surgery
Orchiectomy reduces testosterone-driven behaviors, though not always completely. A study on canine behavior found that objectionable sexual behavior, aggression toward other males, roaming, and urine marking were reduced in roughly 60% of dogs after the procedure. That means a significant number of dogs do improve, but about 4 in 10 show little change. Behaviors that have become deeply ingrained through years of practice are less likely to resolve than those caught early.
In cats, the results tend to be more dramatic. Urine spraying, which intact male cats use to mark territory, often decreases substantially after neutering. The pungent odor of intact male cat urine also becomes much less intense. Roaming behavior, which puts cats at risk of traffic injuries and fights, drops significantly.
When to Schedule the Procedure
Timing depends heavily on species and, in dogs, on breed size. Small-breed dogs generally face no increased risk of joint disorders or cancers linked to early neutering, so owners have flexibility in choosing when to schedule surgery. Larger breeds are a different story. Their musculoskeletal systems develop more slowly, and removing testosterone too early can affect bone and joint growth. For giant breeds like Great Danes, veterinary guidelines suggest waiting well beyond the first year of life.
A large-scale study covering 35 dog breeds found that vulnerability to joint disorders after neutering is closely tied to body size. For breeds where no elevated risk was identified, the recommendation is simply to choose the timing that works best for the individual dog and household. For breeds with documented risk, waiting until skeletal maturity (typically 12 to 24 months depending on size) is the more cautious approach.
Cats are typically neutered between 4 and 6 months of age. Horses are commonly castrated as yearlings or two-year-olds, though it can be done earlier.
Orchiectomy in Horses and Livestock
In horses, the procedure is called gelding. It can be performed with the horse standing under sedation or lying down under general anesthesia. Both open and closed techniques are used, and the choice depends on the veterinarian’s preference and the horse’s temperament. One notable difference from small-animal surgery: the scrotal incisions in horses are often left open to drain rather than sutured closed. Closing the incision usually requires removing the scrotal sac entirely to prevent large blood-filled swellings from forming in the enclosed space.
Livestock castration is widespread in cattle, sheep, and pigs, performed primarily to manage temperament and prevent unwanted breeding. The methods vary by species. Pigs are castrated surgically, with the testicles removed through a scrotal incision, because their anatomy doesn’t lend itself well to other approaches. Cattle and sheep have additional options: rubber rings or latex bands applied to the scrotum cut off blood supply, causing the testicles to atrophy and fall off over several weeks. Clamps that crush the blood and nerve supply (a “bloodless” method) are also common. These non-surgical methods are typically used in young animals and avoid the need for incisions, though they carry their own welfare considerations around prolonged discomfort.
Weight Gain and Metabolic Effects
One of the most practical concerns for pet owners is the weight gain that commonly follows orchiectomy. The hormonal shift after surgery changes how the body uses energy. In male cats, research shows that the weight increase isn’t caused by a slower metabolism but rather by increased food intake. Neutered male cats simply eat more. In female dogs (after the equivalent procedure, ovariectomy), fasting metabolic rate drops measurably, meaning they burn fewer calories at rest.
Neutered male dogs face a dramatically higher risk of becoming overweight compared to intact males. Intact males are about 40% less likely to be diagnosed as overweight than their neutered counterparts. This elevated risk is most pronounced during the first two years after surgery, which is the critical window for establishing portion control and exercise habits. The takeaway is simple: after orchiectomy, your pet needs less food or more exercise, often both. Feeding the same amount as before surgery will almost certainly lead to weight gain.
Recovery and What to Watch For
For dogs and cats, recovery from a routine orchiectomy takes 7 to 10 days. During that period, activity needs to be restricted: no running, jumping, swimming, or rough play. These activities put strain on the incision and can cause it to reopen. Baths and swimming are off limits as well, since moisture introduces bacteria to the wound.
Some mild swelling around the surgical site is normal in the first day or two. What isn’t normal, and warrants a call to your veterinarian, includes continuous blood drainage, blood seepage that persists beyond 24 hours, excessive swelling or redness, or any foul-smelling discharge from the incision. Most animals bounce back quickly. Cats in particular often act completely normal within a day or two, though the incision still needs the full healing period regardless of how the animal feels.
Horse recovery is longer and carries higher stakes. Post-operative swelling is expected and can be significant. Controlled exercise, usually hand-walking, helps promote drainage and reduce swelling. Complications like excessive bleeding or infection are more common in equine castration than in small-animal neutering, partly because the surgical environment (often a barn or field) is less sterile than an operating room.