An Ancient Practice but a New Paradigm: Personal Choice for the Age to Spay or Neuter a Dog

Abstract

Extensive practice and knowledge of the methods and effects of castration of male livestock and even humans has been widespread since ancient times, but only a few decades ago did neutering (including spaying) become a routine part of canine husbandry. In the US, the 6-month neuter became standard practice. Only recently, however, have some of the consequences of this major physiological alteration become evident. As the data-based study on 35 breeds reveals, there are major breed differences associated with effects of neutering, especially with early neutering, including increased risks of joint disorders and some cancers. The study of mixed-breed dogs reveals that the risk of joint disorders is increased in the large dogs. Implications of breed-specific and sex-specific effects for age of neutering have prompted the consideration of a new paradigm with regard to this practice. This involves focusing on each individual dog when deciding upon the appropriate age of neutering to avoid increasing the risk of a joint disorder or cancer above that inherent for the breed. For many breeds, particularly the smaller dogs, no effects were found for the age of neutering on joint disorders and the cancers followed. In these cases, the caregiver has a wide range of choice for neutering without increasing the dog's risk for these diseases. In the future, additional research may reveal more about other increased risks for age-related cognitive dysfunction or elevated levels of luteinizing hormone caused by gonad removal, and lead to revised guidelines.

National Dog Survey: Describing UK Dog and Ownership Demographics

“…The motivations, attitudes and behaviours surrounding owners’ decisions to neuter are complex [ 42 ] and further research is needed to better understand both the benefits and risks to the individual and population of neutering to ensure evidence-backed recommendations are made, as well as into the drivers of and barriers to decision-making of owners. The age at which pet dogs should be neutered is contested, with recent scientific literature suggesting timings of neutering should be considered on an individual basis accounting for factors including behaviour, sex and breed [ 43 ]. Historically, owners were recommended to have their dogs neutered around the age of 6–9 months or after their first season for females, which is around 12–15 months [ 40 ]; however, there is limited scientific evidence to suggest a single optimum age.…”

Life tables of annual life expectancy and mortality for companion dogs in the United Kingdom

“…Neutered animals in these cited studies would have already lived to the age of neutering, biasing their life expectancy towards greater length, highlighted by the lowered probability of death at year 0-1 in neutered dogs. As veterinarians may often recommend early neutering for female dogs, sometimes before the start of the oestrus cycle 42 or soon after the first cycle 43 , neutering of females may occur earlier in life than neutering for males 43 . Therefore, the gap of true life expectancy between the sexes due to neutering might be even wider than reported here.…”

Cranial Cruciate Ligament Rupture in Dogs: Review on Biomechanics, Etiopathogenetic Factors and Rehabilitation

“…Connective tissue remodeling and metabolism are the result of the continuous synthesis and degradation of proteins: this process is also regulated by steroid hormones. Therefore, the alteration of the hormonal structure resulting from ovariectomy and orchiectomy can determine a greater predisposition to ligament rupture [ 102 , 108 , 109 ]. Receptors for the luteinizing hormone (LH) have been found inside the ligament: in spayed and neutered animals, an increase in the activation of these receptors results in increased CrCL laxity, making it more susceptible to the onset of lesions.…”