Neutering your dog or cat may help prevent a number of medical as well as behaviour issues, the most important of which are listed below:
Neutering eliminates the risk of testicular cancer. This condition, mostly seen in intact male dogs, is believed to be due to testosterone (from the testicles). It's simple, really: no testicles, no testicular cancer. One more reason to neuter is when a male is cryptorchid, i.e. when a testicle does not come down and remains in the belly. The testicle left in the belly has a much higher risk of becoming cancerous. So this may require 2 surgeries: 1 to remove the "outside" testicle, and 1 in the belly to find and remove the other one. Occasionally, both testicles are in the abdomen.
A perineal hernia is a fixable but annoying problem mostly seen in intact male dogs. Organs from the belly can slip or herninate through weakened muscles in the pelvis. The consequence is a bulge on one or both sides of the anus. The hernia can contain fat, fluid or even the bladder. These hernias classically cause constipation. This condition is believed to be due to testosterone (from the testicles). Neutering dramatically reduces the risk of these hernias.
Intact male dogs can have a number of diseases of the prostate including cysts, abscesses and enlargement. The latter is called “benign prostatic hyperplasia,” just as in older men. Neutering (of dogs!) prevents these problems.
Roaming and getting lost
The problem with an intact male is that it’s hard for him to resist a female in heat! An intact male can run away and follow the smell of a female in heat located miles away.Every year, millions of pets get lost. Some are returned to their owner. Most are not. To decrease the risk of such a tragedy happening in your family, neuter your pet, pet-proof the fence in your backyard and always keep your pet on a leash during walks. In addition, talk to your vet about the benefits of microchips.
Unneutered pets have all kinds of behavioral problems. In male dogs, the most common behavior is an aggressive temper. Of course, there are many intact pets who are perfectly sweet. Neutering, when done early in life, can reduce aggressiveness and improve behavior overall.
Few things smell worse than intact male cat urine. Some people make their indoor cat an outdoor cat when they can't tolerate the smell anymore. This increases the risk of being hit by a car. Neutering, when done early enough in life, virtually eliminates the odor of male cat urine and should prevent marking in male dogs.
Getting into fights
In addition, neutering decreases the risk of getting into fights, notoriously in tom cats. They commonly get abscesses from these fights.