Neutering before one year of age has long been a common practice in the United States and much of Europe. However, growing evidence suggests that the health consequences differ depending on a dog’s size and breed. A study published in July 2020 in Frontiers in Veterinary Science examined over 3,100 mixed-breed dogs divided into five weight categories to assess risks of joint disorders and cancers associated with early neutering.
The weight groups studied were: under 10 kg, 10–19 kg, 20–29 kg, 30–39 kg, and over 40 kg. The researchers analyzed males and females separately and considered the timing of neutering. Joint disorders investigated included hip dysplasia, cranial cruciate ligament (CCL) rupture, and elbow dysplasia. The cancers evaluated were lymphoma, mast cell tumor, hemangiosarcoma, and osteosarcoma.
The results revealed no significant increase in cancer incidence linked to neutering in any weight group. However, for dogs weighing 20 kg or more, neutering before one year was associated with a markedly increased risk of joint disorders, in some cases up to three times higher than that of intact dogs. For the two smallest weight categories, under 20 kg, there was no evidence of elevated risk for joint conditions following neutering.
These findings show that body size plays a crucial role in determining the health risks of neutering. While small mixed-breed dogs appear relatively unaffected, larger dogs are far more vulnerable to orthopedic complications if neutered early. The authors conclude that veterinarians and caregivers should carefully weigh breed size and individual context when advising on neutering decisions.
Source: Hart, B., (Geyer), L. A. H., Thigpen, A. P., & Willits, N. Frontiers in Veterinary Science, July 2020.
