Abstract
The early neutering of male and female dogs and its relationship to an increased risk of joint disorders and some cancers has recently become a concern, raising questions about the standard practice in the U.S. and much of Europe of neutering by 6 months of age. A noteworthy recent finding from this center is that there are major breed differences with small-dog breeds generally showing little vulnerability to neutering compared with breeds of larger body size. These findings on purebreds raise questions for dog owners and veterinarians about mixed-breed dogs. The purpose of this study was to examine a sample of mixed breed dogs of five weight categories using the same veterinary hospital database and diagnostic criteria for joint disorders and cancers as used in the newly published paper on 35 breeds and previous papers on the Golden Retriever, Labrador Retriever, and German Shepherd Dog. The weight categories were <10 kg (739 cases), 10–19 kg (546 cases), 20–29 kg (992 cases), 30–39 kg (604 cases), and over 40 kg (258 cases). Males and females were analyzed separately, as were various ages at neutering. The joint disorders examined were hip dysplasia, cranial cruciate ligament tear or rupture, and elbow dysplasia. The cancers were lymphoma, mast cell tumor, hemangiosarcoma, and osteosarcoma. There was no significant increased occurrence of one or more cancers, compared with intact dogs, in any weight category. However, in the three categories of dogs weighing 20 kg or more, neutering before 1 year generally was significantly associated with risks of one or more joint disorders above that of dogs left intact, commonly to 3 times the level of intact dogs, with sex differences in the degrees of joint disorders associated with neutering. For the dogs in the two weight categories <20 kg, no increased risks were found for joint disorders. This information can be useful to dog caregivers in deciding on the age at which to neuter specific dogs, and for veterinarians offering guidance to pet owners.
Highlights
Neutering male and spaying female dogs at or before 6 months of age has become routine in the US and much of Europe [1]
One study found that hip dysplasia and cranial cruciate ligament tears or ruptures were more likely in neutered than intact males and females [2]
One major finding from the present study is that despite the dogs being of mixed breeds, there was uniformity in the relationship of body weight and association of neutering with increased risks of joint disorders
Summary
Neutering male and spaying female dogs (both referred to as neutering) at or before 6 months of age has become routine in the US and much of Europe [1]. In the US several states require neutering of all dogs before being released for adoption even if this is well before 6 months of age. Investigations have revealed that joint disorders and some cancers may increase in association with early neutering. One study found that hip dysplasia and cranial cruciate ligament tears or ruptures were more likely in neutered than intact males and females [2]. Another study found that neutering was associated with a 3-fold increase in excessive tibial plateau angle [3], which is a risk factor for cranial cruciate ligament disorders. Among studies on specific breeds are those on the Golden Retriever, Labrador Retriever, and German Shepherd Dog, revealing an increase in the incidence of one or more of the joint disorders with neutering in the first year to 2–4 times the 3–5% incidence in intact dogs [4,5,6]
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