Male dogs are "neutered"

Most vets agree that cancer of the testicles and various prostate problems, along with several types of peri-anal tumors, are far more common in un-neutered dogs. Most common are the peri-anal tumors (tumors around the anus) about half of which are malignant.

More common is benign prostatic hyperplasia, which is just a testosterone-driven enlargement of the prostate. It is not cancer, but because of the anatomy (the prostate is sort of like a donut with the urethra running through the middle, and is directly below the colon), when it enlarges to a certain point, the dogs can’t urinate or defecate. At that point, they have to be neutered (getting rid of the testosterone will shrink the prostate), and be put on various drugs so that they can ‘potty’ till it shrinks. Another common problem is prostatitis, or prastatic abcesses (bacterial infections). Same symptoms, plus pain, fever, and just plain sick. Treatment is long-term antibiotics and neutering. At this time the dog may be older and surgery may present a higher risk than it would have if they had been neutered young. At least a fourth of all older intact (un-neutered) dogs have one problem or another.

The most common problem is plain old trauma. Intact dogs slip out looking for girls and get themselves run over, shot, poisoned, or torn up fighting at about 50 to 1 neutered. This doesn’t even address the problem of mating driven behavior such as marking territory by peeing on furniture, humping legs, and aggressive tendencies with other male dogs (the competition). These behaviors may not be present now but can always develop in later years.

Female dogs are "spayed"

Of course, the most obvious reason form spaying your female dog is overpopulation and the resulting mass euthanasia and neglect. There can never be enough good homes for all the puppies and kittens born, including purebreds. Spaying your lady friend avoids heat cycles, unwelcome visitors fighting on the lawn, accidental pregnancies, unwanted puppies and kittens, inconvenience and expense.

Many experts believe spaying results in a better-behaved pet. Spayed pets are less likely to spray (particularly cats), or mark or roam. They are less aggressive toward humans and other animals. Did you know that 85% of dog bites involve intact pets?

Spayed females are healthier pets. Females spayed before their first heat cycle have 96.4% less risk of breast cancer. Spaying after the first heat but before a litter still reduces the risk by 84%. Breast cancer is four times more common in dogs than in humans. Spayed females have no risk of uterine infection, or uterine, ovarian, or cervical cancer. Dogs and cats have their own sexually transmitted diseases, many fatal, and some potentially contagious to humans. Spayed and neutered pets are rarely exposed to these diseases.

Last but not least, as with humans, there are many complications associated with pregnancy, having babies, and raising a litter – infections, emergency C-sections (very expensive), seizures due to calcium deficiency, etc. The risk of pregnancy and rearing a litter is far greater than the risk of anesthesia and spaying