Written by Dr. Jim Berry, Douglas Animal Hospital
The shelter movement in North America has actively educated and encouraged pet owners to spay and neuter their pets as a cornerstone of responsible pet ownership. Many SPCA’s perform early spay/neuter surgeries as early as 8 weeks of age. This practice has undoubtedly reduced the number of unwanted pets and resulting euthanasia of unwanted and un-owned animals, but are there are downsides to the practice?
For cats, there is no current evidence that early spay/neuter causes any health or welfare problems for the kittens or for animals after they mature. In fact, there is a decreased chance of cat to cat aggression; fewer fight wounds, and fewer mammary cancers in female cats.
The story for dogs is more complicated and study is ongoing. At this time, the work is being conducted on large breeds of dogs like Retrievers, Pointers and Rottweilers. There is good early evidence (not 100% confirmed yet) that spaying and neutering before the bones have stopped growing in larger breeds (normally occurs at about 14 months of age) may increase the risk of hip and knee problems such as hip dysplasia and cranial cruciate ligament injury. More of a concern is the relative risk of various cancers. Osteosarcoma, hemangiosarcoma and lyphosarcoma seem to have an increased prevalence in dogs which were spayed/neutered before bone growth had finished. On the flip side, the risk of mammary cancer is significantly lower in female dogs that are spayed before they go through their first heat cycle (normally by 8-9 months of age for large breeds). This data only applies to large breeds, but there have not been any studies on toy breeds yet. There is also some evidence emerging that intact female dogs may fight less and have calmer behaviours than spayed females. Intact male dogs do show increased aggression to other male dogs, but not to people. As you can see, the early data is confusing, but also interesting.
So, are there any options to maintain healthy dogs, and prevent unwanted pregnancies? Ovary sparing surgery (hysterectomy) can be performed on females to leave the ovaries intact, but prevent pregnancies. Male dogs can have a vasectomy instead of the standard castration procedure. Clearly, there are advantages and disadvantages to all options. However, the standard adage of spaying and neutering all pets before they are reproductively mature may need to be reconsidered. The best person to contact about this is your own veterinarian. They can provide you with all of the pros and cons of spaying/neutering based on your lifestyle, type of pet you own, and what risks you are comfortable with.