Beyond Birth Control: 
Why Spay or Neuter Your Pet?
 By Susan Horowitz, D.V.M.

Although the impact on pet overpopulation and therefore on the shelter population cannot be overemphasized, there are important health benefits to your pet as well.

What happens during “heat”:

  • An unspayed female cat or dog has an estrus cycle at the time the pet is able to conceive, known commonly as being “in heat.”  
  • Dogs commonly have swelling of the vulva and may bleed for 3 to 21 days. They attract male dogs during this time. The female dog averages two heat periods a year.
  • On the other hand, a female cat is considered seasonally polyestrus. In other words, most female cats come into heat about January or February and remain in heat until they are bred (as opposed to a dog who will eventually go out of heat). If she is not bred, the hormonal influences continue and often lead to false pregnancy or uterine infection. After a female has a litter, she will come into heat again within a couple of weeks. Most cats do not stop having a heat cycle until the late fall (and some never do). The female cat often makes loud noises or behaves unusually while she is in heat. 
Health problems are more common in intact animals: 
  • Because of hormonal fluxes, it is common for many intact older cats and dogs to have cystic ovaries and uterine infections. The uterus can fill with pus (apyrometra) --a life-threatening situation. Although early treatment is to give the pet antibiotics and fluids, if it is not effective, the veterinarian must remove the uterus and ovaries. Although a simple spay on a younger animal, this surgery becomes serious and much more extensive and dangerous when done on a debilitated animal.
  • Mammary tumors are common in the unspayed female cat and dog.  A high percentage of these tumors are malignant. Studies have demonstrated that mammary masses are very rare in dogs and cats that have been spayed prior to their first heat and much lower in females spayed before a year and a half of age.
  • Male cats that have not been neutered are more likely to wander the neighborhood --especially if there is a nearby female in heat. They are also at a greater risk of diseases such as Feline Leukemia (FeLV) and Feline Immunodeficiency Virus ( FIV). The primary group infected with FIV is intact male cats. 
  • Roaming intact male cats and dogs are also at risk for hazards such as being attacked by other animals and hit by a car. 
  • Intact male cats will probably spray or mark their territory. The urine of an intact male is strong and odiferous and difficult to remove.
  • Many older intact male dogs have prostate problems. A neutered male is less likely to develop prostatic disease.
These health problems are part of the reason that we advocate neutering the dog or cat instead of performing a simple vasectomy.

Myths that spaying or neutering will change your pet’s personality are simply not true. Your pet’s basic personality should remain the same.  However, male dogs may be less aggressive and less likely to wander when they are neutered. The other frequently heard myth that an altered pet will become fat and lazy also has no basis in fact. Just like people, if the pet is exercised and fed properly, it should remain in shape.

There are many health and behavioral benefits to spaying and neutering your pet. But don’t forget when you spay or neuter your pet, not only are you protecting your pet from future health problems, you are also helping to prevent the flood of unwanted, homeless kittens and puppies that enter shelters each year.