Ask a Vet: Is 4 months too young to have my pet spayed or neutered?

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Last week, we introduced a new feature here at Unleashed: Ask a Vet. We’re delighted to have Dr. Heather Oxford, of L.A. veterinary hospital California Animal Rehabilitation (CARE), on board to answer your questions about your pet’s health and well-being. Got a question for Dr. Oxford? Leave a comment on this post, and look for her answer in an upcoming installment of Ask a Vet.

Unleashed: L.A.’s recent spay/neuter law mandates that pet dogs and cats be sterilized by the time they’re 4 months old. Is that an appropriate age for my pet to have surgery?

Heather Oxford, DVM: This is an incredibly complex issue. My opinion is that the city took the right step in creating a spay/neuter law that is enforceable; however, 4 months might be too young according to new scientific studies.

The first problem is that animals that are neutered (gender-neutral term) before their growth plates close grow significantly taller than those who are neutered after their growth plates close. The extra growth can be unevenly distributed through the different bones of the body since the age of each growth plate closure is different for each bone, which can be up to 14 months for larger breeds. For example, this means that the tibia (shin bone) could grow longer than the femur (thigh bone) and cause an abnormal angle of the knee which could cause ligament tears. Therefore, we may see an increase in orthopedic diseases in the future.

There also seems to be an increased risk of bone cancer developing in dogs that were neutered before 1 year of age. However, the benefits of neutering early far outweigh the risks of neutering later when it comes to cancers of the testicle, prostate, and area around the anus. Early neutering shows a very protective effect in mammary cancer, which accounts for 50% of all tumors of female dogs and 20% of all tumors of female cats.

Neutering before the first heat cycle reduces the risk of mammary cancer to 0.05%, whereas waiting until after the first heat cycle increases the risk to 8%. The first heat cycle occurs between 6 months and 18 months, depending on breed.

Increased noise phobias and undesired sexual behaviors have been associated with neutering before 5 1/2 months of age, and there has been a link between early spaying and urinary incontinence in female dogs.

Infectious diseases were found to be more common in dogs neutered at or before 6 months of age compared with those neutered after 6 months in another study. Studies also suggest that increased behavioral issues like fear and aggression may be due to earlier ages at time of neutering.

I assess each pet individually, as most veterinarians do. For an animal whose breeding lines have higher incidence of orthopedic disease, waiting until the animal’s growth plates close to neuter may be the best decision.

Likewise, a female might be neutered earlier than a male of the same breed. I have concerns with this law and would like for the age to be reassessed, however, the benefits of a spay/neuter law such as this include less homeless animals and less animals having to be euthanized at shelters. I am glad that L.A. has started the ball rolling in the right direction.

About our vet: Dr. Oxford received her bachelor of science degree at Bowling Green State University, Ohio. She also received a master’s of public health degree in epidemiology from Emory University and went on to work at the Centers for Disease Control and Prevention in Atlanta. She then went to the University of Tennessee, College of Veterinary Medicine, where she received her doctor of veterinary medicine degree. She practices at California Animal Rehabilitation and is also certified in veterinary rehabilitation and acupuncture. She lives in Los Angeles with her husband, Wade, and German shepherd, Tess.