Aside from helping control the current overpopulation of dogs, neutering a pet dog generally makes for a healthier dog and a better pet. Neutered dogs tend to live longer and have fewer behavior problems (see below). They are less likely to be relinquished to the shelter and do not contribute to over-crowding in community animal shelters with their off-spring. The local government is more interested in having fewer roaming dogs that could be dangerous and having less burden on the animal services budget. Pet owners are more interested in having a well-behaved and long-lived family pet.
There are several health benefits to neutering. One of the most important concerns the prostate gland, which under the influence of testosterone will gradually enlarge over the course of the dog’s life. By age five years, it is usually significantly enlarged in an unneutered male dog. As the dog continues to age, his prostate is likely to become uncomfortable, possibly being large enough to interfere with defecation. The prostate under the influence of testosterone is also predisposed to infection, which is almost impossible to clear up without neutering. Neutering causes the prostate to shrink into insignificance, thus preventing both prostatitis as well as the uncomfortable benign hyperplasia (enlargement) that occurs with aging. It is often erroneously held that neutering prevents prostate cancer but this is not true; neuter benefits on the prostate are about preventing enlargement and infection.
Other health benefits of neutering include the prevention of certain types of hernias and tumors of the testicles and anus. Excessive preputial discharge is also reduced by neutering.
Numerous studies on the behavioral effects of neutering have been performed evaluating playfulness, fear of strangers, territorial aggression, mounting, urine-marking, roaming and other behaviors. The behaviors that are most consistently altered after neutering are inappropriate mounting, urine marking, and fighting. These behaviors were significantly reduced or completely eliminated in 50-60 percent of male dogs after neutering. Most pet owners look forward to curtailing these actions and thereby improving their relationship with the dog.
An incision is made, generally just forward from the scrotum. The testicles are removed through this incision. The stalks are tied off and cut. Castration is achieved. If the testicles are not removed, the desirable benefits listed above cannot be realized. The skin incision may or may not have stitches.
Male dogs can be neutered at just about any age though the traditional age for neutering is six to nine months of age, which is still before puberty. There is some controversy regarding when the best age for neutering should be: after puberty, traditional age or "early", which can mean any age from eight weeks up to six months. Senior dogs can also benefit from neutering. A diseased, enlarged prostate will still shrink down to a comfortable size even in an older dog. The neuter is a relatively simple low-risk surgery, which means that even an older dog can still benefit.
The younger the pup is at neutering, the longer his long bones will continue to grow, which changes his conformation to a taller stature. This appears to have some musculoskeletal consequences, though surgical recovery at younger age is faster and there are fewer complications with the neuter itself.
Metabolism changes with neutering in such a way that there is a moderate risk of becoming overweight after neutering. The dog owner should be prepared to make adjustments in diet or exercise if the dog seems to be gaining too much weight.
His interest will be reduced but if he is around a female dog in heat, he will become aroused by her. Mounting behavior often has roots in the expression of dominance and may be expressed by a neutered male in a variety of circumstances that are not motivated by sexuality.
Undescended testicles have an increased tendency to grow tumors. They may also twist on their stalks and cause life-threatening inflammation. For these reasons, neutering is recommended for dogs with undescended testicles. If there is one descended testicle, the dog will be able to breed but since retaining a testicle is a hereditary trait, it is important that the male dog not be bred before he is neutered. It is not a good idea to pass on the retained testicle trait.
In some areas, neutering may be required as municipalities attempt to prevent pet overpopulation. Check with your local city or county officials.