Commercial dog breeding establishments, often referred to as puppy mills, are large-scale operations where dogs are confined in cramped enclosures with little to no exercise, enrichment, or positive human interaction.
The sole purpose of these facilities is to maximize profit by mass-producing puppies, which are sold through pet stores and online platforms.
Two major scientific studies provide conclusive evidence that puppy mills cause severe and long-term harm to both adult breeding dogs and puppies sold through these channels.
Study 1: Adult Breeding Dogs from Puppy Mills
Researchers
- Franklin D. McMillan, DVM, Best Friends Animal Society
- Deborah L. Duffy, Ph.D., University of Pennsylvania School of Veterinary Medicine
- James A. Serpell, Ph.D., University of Pennsylvania School of Veterinary Medicine
Published Paper
“Mental health of dogs formerly used as ‘breeding stock’ in commercial breeding establishments.”
FD McMillan, DL Duffy, JA Serpell. Applied Animal Behaviour Science (2011); 135: 86–94.
Findings
The study compared 1,169 former breeding dogs from commercial breeding facilities with pet dogs from the general public. Results showed:
- Elevated levels of fears and phobias
- Pronounced compulsive and repetitive behaviors (e.g., spinning, pacing)
- House soiling and difficulty adjusting to normal environments
- Heightened sensitivity to touch and handling
The psychological harm was severe, long-lasting, and often irreparable, persisting for years or even throughout the dog’s life.
- Existing state and national laws fail to protect breeding dogs from psychological harm.
- Legislation should be updated to reflect modern animal welfare science and prioritize mental well-being.
Study 2: Puppy Mill Puppies
Researchers
- Franklin D. McMillan, DVM, Best Friends Animal Society
- James A. Serpell, Ph.D., University of Pennsylvania School of Veterinary Medicine
- Deborah L. Duffy, Ph.D., University of Pennsylvania School of Veterinary Medicine
- Elmabrok Masaoud, Ph.D., Atlantic Veterinary College, University of Prince Edward Island
- Ian Dohoo, DVM, Ph.D., Atlantic Veterinary College, University of Prince Edward Island
Published Paper
“Differences in behavioral characteristics between dogs obtained as puppies from pet stores and those obtained from noncommercial breeders.”
FD McMillan, JA Serpell, DL Duffy, E Masaoud, IR Dohoo. Journal of the American Veterinary Medical Association (2013); 242: 1359–1363.
Findings
The study compared 431 adult dogs purchased as puppies from pet stores with those from small-scale private breeders. Results showed pet store dogs exhibited:
- Greater aggression toward family members, strangers, and other dogs
- Increased fearfulness of other dogs and everyday events
- Higher rates of separation anxiety and house soiling
For no behavioral category did pet store dogs perform better than breeder-obtained dogs.
- Dogs from pet stores are at higher risk of developing serious behavioral problems.
- Stricter regulation of commercial breeding conditions is needed to reduce risks to puppies and their future owners.
