Delay neutering of large mixed-breed dogs, study says

UC Davis researchers say the early fixing of heavy dogs may increase the risk of joint disorders

Heavier mixed-breed dogs are at greater risk of health complications if neutered or spayed early.

This is according to new study by researchers at University of California, Davis (UC Davis), which analyzed 15 years of data from thousands of dogs at the university’s Veterinary Medical Teaching Hospital.

The study, researchers say, found mixed-breed canines weighing more than 44 lbs. (19.9 kg) as adults were more likely to develop one or more joint disorders if neutered before the age of one.

Researchers examined common joint disorders, including hip dysplasia, elbow dysplasia, and cranial cruciate ligament tears (a knee injury), in five weight categories.

They found the risk of these disorders in altered large mixed-breed dogs to be a few times higher compared to dogs left intact. For example, for female dogs weighing more than 43 lbs., the risk jumped from four percent for intact dogs to 10 to 12 percent if spayed before a year of age.

Standard practice in North America and much of Europe dictates spaying/neutering dogs by six months of age, UC Davis says. Additionally, neutering/spaying prior to adoption is a common requirement or policy of humane societies, animal shelters, and breeders.

This study suggests a need to review and modify these policies, researchers say, particularly for young mixed-breed dogs that will grow large in size.

“The study raises unique challenges,” says the study’s coauthor Lynette Hart, PhD. “People like to adopt puppies from shelters, but with mixed breeds it may be difficult to determine just how big the dog will become if you don’t know anything about the dog’s parents.”

“Most dogs are mixed breeds,” adds lead author, Benjamin Hart, DVM, PhD. “We hope this study will influence the spay or neuter process to give people wishing to adopt a puppy the time to make an informed decision on when to spay or neuter.”

The findings especially relevant for people and organizations raising service dogs, Dr. Hart explains.

“They need to take a serious look at this,” she says. “Joint disorders can shorten a dog’s useful working life and impact its role as a family member.”

The study, which also features coauthors Abigail Thigpen, BS, and Neil Willits, PhD, has been published in Frontiers in Veterinary Science. For more, click here.

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