Welcome Back to Science Sunday
Whether or when to neuter dogs and bitches has been on ongoing matter of controversy for as long as the procedures have existed. Given that in the majority of cases whether to neuter is obvious, we will turn our attention to when. Much of the controversy is anecdotal and not based on scientific fact. Others are well documented such as certain cancers and joint disorders.
A 2013 study into Golden Retrievers by the University of California, turned the world of veterinary medicine on its head concerning early spaying and neutering. Early sterilization prevented many issues, according to the study, but also appeared to increase the risk of other diseases, such as cranial cruciate ligament rupture, hemangiosarcoma, mast cell tumors, lymphosarcoma, and hip dysplasia. The study concluded that more studies on the link between sterilization age, breed and the onset of certain diseases also are needed.
Well now those studies have been done. A new study, also from University of California, carried out over 10 years involved 35 different dog breeds. From the thousands of dogs examined every year at UC Davis Veterinary Medical Teaching Hospital, the researchers examined 15 years of data to determine whether neutering, the age of neutering, or differences in sex when neutered affect certain cancers and joint disorders across breeds.
Perhaps as may be expected, joint problems were more related to body size than neutering. That being said, there were some surprising statistics emerged in some breeds. For example, the incidents of cancer in small breeds was found to be low whether neutered or not EXCEPT in Boston terrier and the shih tzu. In those two breeds, there was a significant increase in cancers with neutering. Below is a table copied from the study outlining the recommended age to neuter for the breeds studied. The column in the table labelled "CHOICE" indicates the age of neutering did have any effect on disease. There was also a comprehensive breed by breed description in the study which you can see HERE scroll about 1/4 way down for the breed specific descriptions.