A major new UK study has raised fresh concerns about the welfare implications of breeding dogs for extreme body size, after finding that giant breeds live significantly shorter lives and experience higher rates of disease than the wider dog population.
Researchers from the Royal Veterinary College’s (RVC) VetCompass Programme analysed anonymised veterinary records from more than 2.25 million dogs receiving primary veterinary care in the UK during 2019. The study included 28,345 giant breed dogs, with a detailed review of clinical records from over 4,300 individuals to assess their health, causes of death and lifespan.
The findings, published in Companion Animal Health and Genetics, suggest that while giant breeds remain popular family companions, their extreme size may come at a considerable welfare cost.
Giant dogs live more than three years less
Perhaps the most striking finding was lifespan.
The study found that giant breed dogs had an average lifespan of just 8.9 years, compared with the previously reported VetCompass average of around 12 years for the overall dog population in England.
Researchers suggest this supports growing evidence that the rapid growth required to achieve very large body size is associated with accelerated ageing and reduced longevity.
Among individual breeds, there were marked differences. Female giant breed dogs lived, on average, 0.8 years longer than males (9.3 years versus 8.5 years), while some breeds had particularly short lifespans. The Tibetan Mastiff recorded the lowest average lifespan at just 4.8 years.
Higher levels of disease
Health problems were also common.
Almost three-quarters (73.8%) of giant breed dogs had at least one disorder recorded during the study period, compared with 65.8% of dogs overall in the wider VetCompass population.
The most frequently affected body systems were:
- Skin disorders
- Musculoskeletal disease
- Ear disease
The three most common individual conditions were:
- Ear infections (8.2%)
- Overweight or obesity (8.0%)
- Aggressive behaviour (5.6%)
The reported frequency of aggression was more than double that previously recorded across the general dog population (2.2%), highlighting the importance of behavioural assessment, early socialisation and responsible ownership.
Cancer remains the leading cause of death
Cancer was identified as the most common cause of death among giant breeds, adding to previous evidence that many large and giant breeds have an increased susceptibility to certain cancers.
The study also confirmed the heaviest giant breeds included:
- Irish Wolfhound (average 64.0kg)
- Saint Bernard (65.1kg)
- Great Dane (60.5kg)
The most commonly owned giant breeds in the UK were the Dogue de Bordeaux, Alaskan Malamute and Akita.
Welfare implications of breeding for extreme size
Lead author Professor Dan O’Neill said the findings raise important questions about how far selective breeding should push physical extremes.
He noted that humans have created extraordinary diversity in domestic dogs through selective breeding, but that giant breeds appear to pay a substantial price in both health and longevity because of their extreme body size.
Professor O’Neill suggested that gradually breeding towards more moderate body sizes within these breeds could improve both lifespan and quality of life while preserving the characteristics that owners value.
The findings add to an expanding body of research examining the welfare consequences of breeding dogs for exaggerated physical traits. Much recent attention has focused on brachycephalic (flat-faced) breeds and dogs with excessive skin folds, but the new study highlights that extreme size should also be considered an important welfare issue.
Dr Julian Hoad, Senior Vice President of the British Small Animal Veterinary Association (BSAVA), welcomed the research, stating that it strengthens the evidence needed to support healthier breeding practices and improve canine welfare.
What does this mean for owners?
The researchers stress that giant breeds can make excellent companions, but prospective owners should be aware that these dogs are likely to:
- Have considerably shorter lifespans than average dogs.
- Be more likely to develop health problems during their lifetime.
- Require ongoing veterinary care, particularly for musculoskeletal disease, obesity and cancer.
- Benefit from careful weight management and preventative healthcare throughout life.
For existing owners, the findings reinforce the importance of regular veterinary checks, maintaining an appropriate body condition, early investigation of health problems and selecting breeders who prioritise health over exaggerated size.
As evidence continues to accumulate on the welfare impacts of breeding for extreme physical characteristics, the authors suggest that future breeding strategies should place greater emphasis on producing healthier, longer-lived dogs rather than simply larger ones.
Reference
O’Neill DG, Curtis TJ, York GOJ, Brodbelt DC, Church DB, Engdahl KS. Giant dog breeds under primary veterinary care in the UK: demography, common disorders and mortality. Companion Animal Health and Genetics (2026). DOI: 10.1186/s40575-026-00152-7
Further reading
- Royal Veterinary College. Living it large: New RVC research reveals health and lifespan challenges in giant breed dogs. Published 26 June 2026.
