More on the Effects of Spaying and Neutering Dogs

By Jennifer Coates, DVM on Aug. 25, 2014

In 2013, we talked about a study looking at the effects that neutering (a term that includes both spaying of females and castration of males) had on the incidence of hip dysplasia (HD), cranial cruciate ligament tear (CCL), lymphosarcoma (LSA), hemangiosarcoma (HSA), and mast cell tumor (MCT) in Golden Retrievers. The dogs were classified as being intact or neutered early (<12 mo) or late (≥12 mo). The researchers found increases in the incidence of some of these diseases in specific sub-classes of neutered dogs (e.g., HSA in late neutered females).

I found that study interesting but thought it oversimplified the situation. For instance, if you are the owner of a male Golden Retriever and are only interested in avoiding lymphosarcoma, then you should not neuter your dog before the age of 12 months. Most owners aren’t looking for that sort of information, however. We simply want to know what we should do to keep our dogs as healthy as possible for as long as possible.

Recently, some of the same scientists responsible for the 2013 study published the results of a similar investigation comparing the health effects of neutering in Labrador and Golden Retrievers. While this isn’t a huge increase in the breadth of the research, it did bring to light some important differences relating to breed.

The dogs were divided into narrower age ranges at time of neutering this time around, specifically:

before 6 months of age
6-11 months of age
age 1
ages 2-8

The scientists also looked at a greater number of conditions — hip dysplasia, cranial cruciate ligament tear, elbow dysplasia, lymphosarcoma, hemangiosarcoma, mast cell tumor, and mammary cancer. They found that the results for the Golden Retriever were “similar to the previous study, but there were notable differences between breeds.” For example:

In Labrador Retrievers, where about 5 percent of [unneutered] males and females had one or more joint disorders, neutering at <6 mo. doubled the incidence of one or more joint disorders in both sexes. In male and female Golden Retrievers, with the same 5 percent rate of joint disorders in intact dogs, neutering at <6 mo. increased the incidence of a joint disorder to 4–5 times that of intact dogs. The incidence of one or more cancers in female Labrador Retrievers increased slightly above the 3 percent level of intact females with neutering. In contrast, in female Golden Retrievers, with the same 3 percent rate of one or more cancers in intact females, neutering at all periods through 8 years of age increased the rate of at least one of the cancers by 3–4 times. In male Golden and Labrador Retrievers neutering had relatively minor effects in increasing the occurrence of cancers.

These findings are striking. If I owned a female Golden Retriever and was told that by choosing to neuter her, I was making it three to four times more likely she would develop one of these cancers, I’d certainly give that decision a second look. On the other hand, if I was told the same decision would only result in a “slight” increase for my female Lab, I’d probably move ahead.

Overall, I do think research is starting to point to an overall positive effect on longevity in dogs who are not neutered (or at least not neutered early), but only when the downsides of not neutering are controlled for. It’s all well and good to say you are going to protect your dog’s joints by keeping him intact, until he leaps the fence to get to a female in heat and is hit by a truck. I still believe that neutering is right for all but those dogs with the most detail-oriented of owners.