young white dog

Spaying or Neutering Your Dog

How we can help

Call 530-752-1393 to schedule an appointment with the UC Davis veterinary hospital small animal clinic.

Spaying or Neutering Your Dog

The main reasons for spaying or neutering (castrating) dogs include reducing pet overpopulation, lowering hormone-associated health problems, and modifying undesirable behaviors. Spaying or neutering a dog that is not intended for breeding purposes is one way in which you can help insure the health and safety of your pet and their place in your family.


Each year thousands of animals are relinquished to animal shelters as a result of unplanned pregnancies and undesirable behavior. Many of these healthy dogs and puppies are euthanized due to a lack of adoptive homes, space and resources. Spaying and neutering dogs that are not going to be used for breeding purposes helps to decrease the number of unwanted breedings.

What is a spay? What does the surgery involve?

Spaying is a surgical procedure to remove the female reproductive organs - the ovaries and uterus. For routine spaying, the best age for dogs is before puberty. Spaying is considered a routine abdominal operation. The procedure is done with the animal under general anesthesia and consists of a small incision in the abdomen for removal of the ovaries and uterus. Recovery is generally prompt. Most dogs can go home the day after surgery and are back to normal within five to seven days.

What are the advantages of spaying?

  • Spayed animals no longer feel the need to roam to look for a mate, they stay home and have less chance of being involved in traumatic accidents such as being hit by a car, lower incidence of contracting contagious diseases, and fewer dog fights.
  • Dogs spayed before their first heat (six months of age) are virtually assured of not developing mammary cancer, a relatively common disease in unspayed females.
  • Spayed pets cannot develop the uterine infection called "pyometra," which occurs commonly among older, unspayed dogs. Pyometra is a life threatening disease.
  • Heat cycles: Spayed animals do not go through heat cycles or produce unwanted puppies. “Heat” refers to the time when female dogs prepare for mating and pregnancy. Dogs have their first heat at 5 to 12 months of age, and heat cycles occur approximately every six months. The external genitals swell, a bloody discharge occurs, and females attract males. Heat cycles generally last from 21 to 30 days and can be inconvenient.

Answers to Common Questions

  • Spaying will NOT make your dog fat and lazy unless she is overfed.
  • It is NOT true that a dog should have one litter before being spayed. This only leads to more unwanted puppies.
  • Spaying will NOT change your pet's personality. Dogs' personalities do not fully develop until between one and two years of age. If your pet's personality changes after spaying at an early age, it would have changed without surgery.
  • A small percentage of spayed dogs have trouble holding their urine when they reach old age. This can usually be controlled by medication.

What is neutering?

Neutering is a surgical procedure to remove the male reproductive organs - the testes. The procedure is performed with the animal under anesthesia and consists of a small incision in the scrotum for removal of the testes.

What are the advantages of neutering?

  • Urine marking, roaming, and mounting are reduced in 75% of male dogs, and aggression is reduced in 33% after castration.
  • Neutering a male dog does not reduce his energy level or ability to work. Obesity can occur if adjustments are not made for the resultant reduced caloric requirement post castration (approximately 25%).
  • Elevated androgens (testosterone) in non-castrated males can contribute to potentially life threatening diseases.
  • Inflammatory and infectious conditions such as orchitis and epididymitis (inflammation of the testis and epididymus), prostatitis (inflammation of the prostate gland) and perianal adenomas (tumors of the anal area) occur more frequently in non-castrated males.
  • Perineal hernias are more common in non-castrated animals.
  • Testicular cancers such as Sertoli cell tumors, Leydig tumors and seminomas also occur more commonly in non-castrated individuals.

When should my dog be spayed or neutered?

Spaying or neutering dogs before one year of age is common in the United States (U.S.) and Europe. Several states in the U.S. require dogs to be spayed or neutered prior to adoption. However, some dog breeds have higher risks of developing certain cancers (lymphoma, mast cell tumor, hemangiosarcoma, osteosarcoma) and joint disorders (hip dysplasia, cranial cruciate ligament tears or ruptures, elbow dysplasia) if spayed within their first year of life.

A 10-year study by UC Davis researchers that examined 35 dog breeds found that this varies greatly depending on the breed. In most breeds examined, the risk of developing problems was not affected by age of spaying or neutering.

Vulnerability to joint disorders was found to be related to body size, with the majority of the larger breeds tending to have joint disorders. Two giant breeds - Great Danes and Irish Wolfhounds - did not show any increased risk to joint disorders when spayed or neutered at any age.

The occurrence of cancers in smaller dogs was low, whether spayed, neutered, or intact. However, in two small breeds, Boston Terriers and Shih Tzus, spaying and neutering was associated with a significant increase in cancers.

In some cases, the sex of the dog made a difference with respect to spaying or neutering related health risks.  Female Boston Terriers spayed at six months of age, for example, had no increased risk of joint disorders or cancers compared with intact dogs, but male Boston terriers neutered before a year of age had significantly increased risks.

The study provided a set of guidelines for each of the 35 breeds studied to assist owners and veterinarians in making decisions about spaying and neutering.

A follow-up study looked at these risk factors in dogs of different weight categories and found no increased occurrence of cancers, as compared to intact dogs, in any weight category. However, in the three heaviest weight categories, dogs spayed or neutered before one year of age were three times more likely to develop joint disorders than intact dogs.

This study aimed to provide guidelines on spaying and neutering for mixed breed dogs.

*This article may not be reproduced without the written consent of the UC Davis School of Veterinary Medicine.

Primary Category