Neutering Your Pet Can Improve Health and Behavior
April 18, 2006
An archive of Pet Columns from the University of Illinois College of Veterinary Medicine is available online at Requests for reprints of this article may be directed to Mandy Barth,

Spring is here and love is in the air, but when dogs and cats start getting romantic, unwanted puppies and kittens can be the result. In the United States, millions of dogs and cats, including purebreds, end up homeless or euthanized each year as a result of pet overpopulation.

In addition to minimizing the pet overpopulation problem, or spaying or castrating (both procedures are known as "neutering") your pet has biological and behavioral benefits, especially if performed while the pet is young.

According to Dr. Kathleen Ham, veterinary surgery resident at the University of Illinois Veterinary Teaching Hospital in Urbana, the foremost benefit for spaying female dogs and cats is reducing the risk of mammary and reproductive tract tumors. Mammary cancer is a common cancer in unspayed canine and feline females, and this type of cancer is influenced by the hormones that surge with puberty and the first heat.

The first heat is usually between 9-10 months of age for dogs (but may occur as early as 6 months) and 6-9 months for cats. Dogs generally have two heat cycles per year, while cats have cycles every three to four weeks during seasons when there is more daylight (spring through fall in the northern hemisphere).

Dr. Ham explains, "Spaying a dog before the first heat can greatly reduce the incidence of mammary cancer in dogs. By removing the ovaries and uterus (known as an ovariohysterectomy or spay) before the first heat, we prevent the first flux of hormones."

Studies in dogs have shown that the risk of developing mammary cancer is 0.05 percent if the dog is spayed before the first heat, 8 percent if spayed after the first and before the second heat, and 26 percent after the second heat. In cats there is a 91 percent reduction in the risk if spayed before 6 months, an 86 percent reduction if spayed before 1 year, and 11 percent if spayed between 13-24 months. Other biological benefits of spaying include eliminating a risk for ovarian and uterine tumors and infections, both of which become more of a risk as a dog gets older.

"Of course, spaying also eliminates unwanted pregnancies which, in addition to contributing to overpopulation, can cause difficulties for the mother." Some animals can have complications during pregnancy or whelping. In addition, spaying a pet can spare a pet owner from dealing with the bloody discharge and anxious, moody nesting behavior of dogs and the obsessive yowling of a frustrated cat.

For males, the main benefits of neutering, or castrating, are behavioral. "Female behavioral problems appear around the time of their estrous cycles, but with intact males, behavior is a year round problem, since they have constant flow of testosterone."

Common problems with un-neutered, or intact, males include urine marking or "spraying" behavior, and male cat urine has a very strong odor. Year round, intact male cats and dogs are prone to wandering behavior, which indirectly affects their physical health by making them susceptible to cars, fights, getting lost or picked up by animal control, and diseases from wild animals or other strays. Neutering males, which is the surgical removal of the testicles, reduces testosterone levels, decreasing the urge to roam, marking behavior, and in cats, the odor of the urine.

Direct health benefits of neutering include eliminating the risk for testicular tumors. Benign overgrowth of the prostate, a disease commonly seen in older intact males, is exacerbated by testosterone, and as the prostate gets bigger it can press on the adjacent urethra, causing urinary problems. Also, certain tumors of the anal area are also testosterone-dependent. Often when dogs with these conditions are neutered, these growths shrink away since the testosterone supply is cut off.

Male cats and dogs reach puberty or sexual maturity between 6 and 12 months of age. "Neutering (both females and males) is best done before puberty to prevent hormone surge and accidental pregnancy, which could complicate a spay," explains Dr. Ham. With proper surgical and anesthetic techniques, neuters can be performed safely on animals as young as 8 weeks of age.

Dr. Ham notes that even though there are many benefits to spaying and neutering many people may be reluctant to have the procedures done. "Humans are more emotionally attached to body parts than animals are, and sometimes project that onto their pets.

"Dogs and cats are not emotionally attached to their genitalia, and they are not going to decide later in life that they want to reproduce. In addition to reducing the number of unplanned pregnancies, spaying or neutering your pet early can prevent a lot of problems later and overall can improve the quality of life for your pet."

For more information about neutering your pet, consult your veterinarian.

An archive of Pet Columns from the University of Illinois College of Veterinary Medicine is available online at Requests for reprints of this article may be directed to Mandy Barth,

Veterinary Extension/Office of Public Engagement University of Illinois College of Veterinary Medicine 217/333-2907