The Science Behind Saying, “No” to a Pet Store Puppy

Approximately one year ago I told you about animal welfare advocate, Dr. Frank McMillan’s study documenting the increased incidence of behavioral abnormalities in adult dogs rescued from puppy mills. This important research provided scientific documentation that these animals come part and parcel with a plethora of negative behaviors.

Dr. McMillan has done it again. This time, his research focuses on puppies purchased from pet stores, the vast majority of which are born in commercial breeding facilities (aka, puppy mills). The most recent edition of the Journal of the American Veterinary Medical Association features Dr. McMillan’s research documenting the behavioral differences between puppies obtained from pet stores and those obtained from noncommercial (non-puppy mill) breeders.

As Dr. McMillan states,

It has long been an article of faith among veterinarians and canine professionals that dogs obtained as puppies from pet stores have a higher prevalence of health and behavioral problems. However there has been a dearth of empirical studies to support this notion.

Research results

Dr. McMillan and his fellow researchers found that pet store dogs received less favorable scores than breeder-obtained dogs for almost every behavior variable measured. In no behavioral category did the pet store group achieve a more desirable score than the breeder group.

Pet store dogs were significantly more likely to exhibit aggression towards human family members, unfamiliar people, and other dogs. They were also more likely to have separation anxiety and touch sensitivity. Additionally, dogs originating from pet stores were more excitable, energetic, and attention seeking and generally less trainable. Lastly, they exhibited higher frequencies of negative behaviors such as escaping from the home, mounting of people and objects, and urinating and defecating in the house.

The authors theorize that stress experienced in a commercial breeding/puppy mill environment during the formative stages of a pet store puppy’s life negatively impacts brain development. There is also evidence that prenatal stress (stress experienced by the pregnant female) can alter normal behavioral development of her offspring. Specifically mentioned stressors include confinement to a small space, extreme temperatures, negative interactions with kennel staff, inability to regulate exposure to negative stimuli, and limited access to positive interactions with humans.

The researchers acknowledged that those who purchase puppies from pet stores might use different methods of training compared to those who purchase from noncommercial breeders. The current study did not investigate this variable.

I wholeheartedly applaud this terrific research. The more scientific substantiation we have to underscore the insanity of purchasing puppies from pet stores the better.

Have you lived with and/or trained a pet store pup? If so, how did it go?


Best wishes,

Nancy Kay, DVM

Diplomate, American College of Veterinary Internal Medicine
Author of Speaking for Spot: Be the Advocate Your Dog Needs to Live a Happy, Healthy, Longer Life
Author of Your Dog’s Best Health: A Dozen Reasonable Things to Expect From Your Vet
Recipient, Leo K. Bustad Companion Animal Veterinarian of the Year Award
Recipient, American Animal Hospital Association Animal Welfare and Humane Ethics Award
Recipient, Dog Writers Association of America Award for Best Blog
Recipient, Eukanuba Canine Health Award
Recipient, AKC Club Publication Excellence Award
Become a Fan of Speaking for Spot on Facebook

Please visit to read excerpts from Speaking for Spot and Your Dog’s Best Health.   There you will also find “Advocacy Aids”- helpful health forms you can download and use for your own dog, and a collection of published articles on advocating for your pet’s health. Speaking for Spot and Your Dog’s Best Health are available at,, local bookstores, and your favorite online book seller.


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16 Comments on “The Science Behind Saying, “No” to a Pet Store Puppy

  1. You cannot put a general conclusion on every dog that has been purchased from a pet store that most of them are going to go bad because the nurture part will bring a lot of change in them once they are handled by good pet parents.

  2. “If pet store puppies or puppy mill dogs are as horrible as they are made out to be, then why are people encouraged to adopt them through rescues and shelters? Are they somehow better pets because they are now “rescues” than they were when bought in a store?”

    I’m pretty sure that based on behavior, I have a former mill dog. She had evidence of having had a litter of puppies before she was one year old (she still had hanging mammary tissue when we adopted her). She suffers from all of the behavioral problems listed in the article and is not the easiest dog to own or live with. She tries hard and is adorable and will be my well-loved dog for her entire natural life. That said she is the fourth consecutive rescue train-wreck we’ve “adopted” and will be the last. There was a time when we obtained our pets from responsible breeders and that is the route I plan to use in the future. I’m sorry, but a dog should be a joy, not a penance.

  3. While I plan to get future puppies from breeders, simply because I believe in preserving my breed of choice and since I don’t breed myself anymore I support those who make sure that future generations will have great working dogs to protect their livestock and/or families or just great pets. However I do not fool myself thinking that buying from a breeder is a guarantee that the dog will be healthy and have a nice temperament. All a breeder can do when producing a litter is selecting parent dogs based on what we know about the dogs and their relatives, that’s as far as how much control the breeder has about the outcome of that breeding, the rest is how nature/genetics work out with those two dogs. A breeder can do everything right and still produce a litter that is a mess. I believe that breeders have been shooting themselves in the foot by providing guarantees about the quality of their puppies. How can one guarantee something that they don’t have control over? A few years ago I was looking for a Jack Russell terrier and I did go to a large shelter in the hope to find a dog. They actually had several available, but in the end I left without a dog, simply because there is no way to evaluate the temperament and health of a dog in such a situation. I then asked around if anybody knows a good breeder and located one that had just taken back a 1 year old male from her breeding. He was exactly as described and has been very healthy since I have gotten him, he is now 8 1/2 years old and when the breeder travelled to some sports events in the area I got to meet both his parents and his grandmother. I do believe one can find a nice rescue dog if one knows what to look for, I always tell people to look for a rescue organization that has foster homes and to look for a dog that has been in the foster home for several months and has been thoroughly evaluated as far as temperament goes. Any current health issues would show up if a dog has been in a home for a while, so chances would be good to get a fairly sound dog that way.

  4. I have to confess my first dog as an adult came from a pet store. This was back in the mid-80’s, before the internet, and I had no idea that puppy mills existed. I purchased a Cardigan Welsh Corgi, a breed I had never heard of before. (I wasn’t even familiar with the much more common Pembroke WC). He was only 7 weeks old and had already been at the store for almost 2 weeks! Hind sight and plenty of education later, I know how horrible that is! At the time, me being young and naive, all I saw was an incredibly cute puppy. But if you are expecting me to now recount a horror story of problems, I can’t. This little dog was incredibly intelligent, and very biddable. I took him to a basic obedience class and he was beyond any doubt the star pupil! He definitely had typical herding dog issues with bossiness and boundless energy, but that was easily managed with plenty of exercise and the love of his life, his frisbee. He was as healthy as a horse his whole life. He did develop IVDD at around 9 years old but even the best bred CWC today can suffer from this. He lived to the ripe old age of 17! Man, how I loved that dog!

    I have two CWCs today because of what a fabulous dog he was. Of course, I now know all about puppy mills and would never, ever buy a pet store dog. Fortunately, CWC breeders work very hard at keeping the breed out of the clutches of puppy millers. Not being a particularly popular breed helps a lot. The pet store buying public seems more interested in the poo’s and the doodles, and unfortunately the Pembroke corgis.

  5. Some people who describe themselves as animal advocates are a different breed of animal than others. Some enjoy saving/rescuing animals. Some enjoy rehabilitating rescued animals. But some people love cats, or dogs, and just want to bring one (or more) into their homes to enjoy. Why does it have to be either/or?

    When I took a puppy from a friend whose dog had an accidental litter I had no expectations. I had her for 14 years and I considered her behavior was average for a dog who had no formal training. Yes, she misbehaved sometimes, like occassionally having accidents in the house, or running out the door, or barking. But most of these behaviors were my fault; for not taking her out often enough, giving her more exercise, keeping her stimulated. But I enjoyed her goofy personality and I missed her when she was gone.

    When I decided it was time for another dog I turned to the shelters and rescues in the area. My heart went out to a lovely 5-yr. old Lab mix with sad eyes. When they told me her history (chained outside w/17 other dogs for her entire life) and that she was severly fearful I had to take some time to think about whether I was up to the challenge. Being an animal lover is one thing…being an animal rehabilitator is another. It has been a long 2 yrs. with some very slow progress, but even though I love her very much and wouldn’t give her up for anything, I would have preferred a dog who I could have enjoyed more, with less effort.

    It’s important for future dog owners, whether they buy or adopt, to be prepared for the committment that is involved when taking a dog into their family. To know the challenges that may come with dogs from puppy mills, pet stores, shelters and rescues. Buying a dog from most reputable breeders comes with a quarantee that the dog is from sound parents and has been properly raised and socialized. If your dog has problems you have recourses. A dog from other sources is pretty much a crap shoot. Either way, prospective dog owners should go in with committment to do their very best to for this new family member and give h/her time to adjust and then give her basic needs with lots of love, patience, care and training. Do your research before you committ. What are your responsibilities as a dog guardian? Be sure you are willing to spend the next 10-20 yrs. giving your dog a good life.

  6. I have adopted three Westies over the last 14 years and only one had been in a private environment. the other two were females from puppy mills that had been breeders, one for ten years and one for five years. Both had some difficult issues in terms of housetraining, riding in a car, shyness, being comfortable around humans, except for me. Yet both were very warm and kind with lovely attitudes and learned a lot in a relatively short time. I don’t know if we do a service by adopting these puppy mill breeders, as they are a lot of training work, but are they better off being left there or euthanized for their lot in life. They won’t be in a pet store, too old and too shy, but i don’t know an easy answer. thanks Patartist

  7. I disagree with this report since it seems biased towards buying a dog from a breeder. Dogs rescued from a shelter should also have been included. I have been rescuing animals for many years- from mass breeding operations, show dogs dumped by their “owners”- breeders who didn’t want a less than perfect dog, dogs from vivisection lab, etc. Like Pam I find that most dogs that have been rescued are very grateful and crave love and attention. Patience, love and non dominance based training go a long way. some may not be the perfect dog, but they all improve.
    The idea that there are “responsible breeders” is ludicrous. Those responsible breeders are creating the mindset that one kind of dog is more desirable than another thereby encouraging puppy mills.
    While living beings can be bought and sold as a commodity (as morally repugnant as that is) and status symbol at an exorbitant price, there will always be those who will try to provide the item at a knockdown price, like a Gucci bag. Like a Gucci bag, that’s all that dogs and other animals are legally-property.

  8. Another thing I have noticed is that on the e-mail groups that are health related or about dealing with behavior problems, the vast majority of the dogs are rescue dogs, it’s very rare that somebody says they got their dog from a breeder. So why don’t we try to turn things around for everybody, the dogs and the people, by trying to increase the numbers of good breeders to decrease the demand for puppies from “puppy mills”?
    Also I used to have a dog training business and there were two pet stores that referred to me, one was Petland and I only once got clients through them for some housebreaking issue that resolved quickly, Petland was giving people a training CD and written instructions with their puppy package and apparently this was sufficient at least on the behavioral end. The other pet store did a great job with socializing their puppies and every single one of the clients I got through this store hired me to get their puppy early training as was encouraged by the store’s owners, none of those puppies had any behavior issues or health issues while they were young. Many of their owners were repeat customers at that store and all their friends and families ended up getting puppies there too. I only knew of one Boston terrier coming from that store that was deaf and the original purchaser took the puppy back to the store when they found out and my friend ended up adopting him, other than being deaf, he was in perfect health and had a temperament to die for. He was an exceptionally snuggly dog and when I would visit, he didn’t hear the bell or me coming in and if I would go to the place he was sleeping and touched him, he would just melt in my hand, he never startled or seemed in any way bothered by a sudden touch, he loved it. And while I would not want to buy a dog from a pet store because I would not want to support the kind of breeder who sends their puppies to a pet store to be sold, the puppies coming from that store where nothing but a delight. And when you think about good business sense, even a pet store won’t be long in business if their “products” are of poor quality. I had a neighbor who got a puppy from a pet store and the puppy was sick when they brought it home, not only did they lose the puppy but their adult dog also got sick and they almost lost her too, but that store wasn’t in business much longer because of the lack of quality which got them in trouble.

  9. Lois you are right on with your comment. If pet store puppies or puppy mill dogs are as horrible as they are made out to be, then why are people encouraged to adopt them through rescues and shelters? Are they somehow better pets because they are now “rescues” than they were when bought in a store? People are being encouraged to adopt through shelters and rescues and being told they can get purebreds through those places, but yet the anti-puppy mill movement cries about the many purebreds ending up in shelters and rescues who are sick and emotionally damaged. I understand there are a lot of people who thrive on adopting special needs dogs, but there are probably a lot more people who want a nice and healthy family pet and are not looking for a problem dog.
    Breeders around the country are going out of breeding because of how difficult it has become to breed and be legal along with being able to obtain the licensing and paperwork with local zoning and animal ordinances that are required. Along with the intrusions of our homes for inspections by animal control or other authorities. I don’t breed anymore, only had one litter 5 years ago, but I have maintained my permit. This makes me subject to animal control being able to show up at my gate at any time they wish and ask to see my home, it does not require a complaint or deficiency, I never had any of those. I just recently had to reason with an officer who wanted to inspect my place at 6.30 am when I was trying to get ready for work and she insisted that unannounced visits are important so the owner won’t have time to fix things up for an inspection. This is what breeders have to put up with these days. We have enough anti-breeder folks in our area, so when somebody applies for a permit, they show up in droves to tell the commisioners not to grant a permit “because we have enough dogs in rescue”. So if somebody does not want a rescue dog and does not want to buy a dog at a pet store, it will become inscreasingly difficult to find a good breeder, which in turn will only encourage less than desirable establishments to sell their puppies to the public. This is never going to end unless good breeders who stand behind their dogs get support so they can provide enough puppies to meet the demand. This is also why you don’t see so many rescue dogs in many (not all) European countries. There are plenty of good breeders and when people want a puppy they are able to locate one within driving distance. Their shelters are usually no-kill shelters and the dogs there are well taken care of and get plenty of socialization by volunteers who can’t have a dog where they live and who want to spend time with dogs. There are no pet stores and there are usually no puppies in shelters there, so puppy buyers go to a breeder. For those who just have to get a rescue dog, they are importing dogs from out of the country to meet the demand for needy dogs.

  10. Not only are there behavioral problems, there are medical problems as well when you get a puppy that was born in puppy mills. I have one that I inherited so to speak and he has several health issues that are hereditary. Not only does he suffer when he gets sick but it makes me so mad that these precious little beings have to live with these issues because of someone’s greed and disregard for living being (the dogs they are using to breed all these puppies). There was one here in this country that had over a 1000 dogs. He was shut down and fined but moved to another state and started all over where he was again shut down and fined again.

    I also have a rescue dog that is a mix of pom & papillon and she is the sweetest and most loving little thing. There are so many wonderful dogs out there in the shelters that need homes that I would never buy one.

    Although, I know that folks don’t like having more rules and regs but someone on the Federal or State level needs to step in and prohibit the puppy mill business. There are many good reputable breeders out there if someone wants a pure bred dog.

    I like Jill want to see them ALL shut down.

    Mary Gardner

  11. Why do people still buy pet store dogs, your article should be required reading for anyone contemplating buying from a pet store. My dogs have all come from shelters and were all great pets. My last rescue was a year ago and the place was full of many different sizes and breeds, there is a dog for everyone there.

  12. Thank you for another great article on this subject, Dr. Nancy. To anyone interested in seeing what the conditions are like in puppy mills, visit our website,, to see USDA-acquired photos of some Iowa mills. So while temperament and health issues associated with the puppies from these places are absolutely significant, the inhumane conditions endured by the parents of these puppies is at the heart of what we’re working on. Wake up, America! Pay attention. Do your homework. Only by making responsible decisions about where you acquire your pet will we be able to put an end to this shameful, slimy industry. NEVER buy a puppy without being able to visit the kennel, see the mother and see where she lives. If you cannot do that, for whatever reason (distance, breeder denies it), do not buy the puppy! You can rest assured that you’re dealing with a puppy mill. Period. Please continue to beat this drum, Dr. Nancy. The dogs need you to.

  13. Frankly Lois, I don’t understand why a person can’t rescue a dog and enjoy it. Other than puppymills, owners turn their dogs in for a variety of reasons and lately it seems to be the economic climate and they are unable to care for their pets properly. You seem to be making the argument that if a dog doesn’t come from a breeder (and I do hope you mean a responsible breeder who sells with a contract and stands behind their dogs) that dog just isn’t worth the time or affection of the owner. Any new dogs, puppy or adult, takes time and there is an adjustment period, some take longer than others and not simply because of where they came from, but breed enters into the equation also.

  14. And yet the public is urged, encouraged and, yes, browbeaten to rescue a dog from a shelter rather than to purchase a well bred dog from a breeder.

    Many of the rescue dogs were from puppy mills and either confiscated in raids or turned over to shelters by their owners. They remain difficult pets with “issues” but now the public is supposed to forgive and endure the problems of a difficult pet. The pleasure seems to come from a self-congratulatory patting themselves on the back for saving a dog rather than actually enjoying their dog.

  15. I am a member of a rescue and have fostered more adult puppy mill dogs than puppies. My finding has been that these dogs are more easily house trained and can make excellent pets. They are grateful for any kindness given them, get along with other dogs and family members.

    Generally the dogs that have come into my home have been seniors, in terrible condition, due basically to lack of care, extremely poor nutrition and in some cases starvation. Many have been deaf, blind or both and still they have the will to live and most come to enjoy life and play with other dogs or family members. It’s a long learning process bu,t it’s exciting to watch the evolution of a dog who has had no socialization come to ask for attention and love. To watch a dog walk in a straight line to the water bowl, rather than circling as it’s been used to all of it’s life is a thrill.

  16. I wholeheartedly concur with these findings. As a trainer of 35 yrs I have seen the number of emotional issues and physical issues increase in my field. I would say that the owners of these puppies have struggled so with these pups that many give up and bring them to the shelter and the adoptees end up calling me for help. I actually now consider pet store puppies to be rescues b/c they have as many or more issues that shelter dogs. Only the people rescuing these pups from pet stores are paying through the nose for this pure bred pup.

    The stats on pure bred dogs ending up in shelters is also on the increase and this is due to these puppy mill/pet store puppies having so many problems physically and emotionally. The whole thing is very sad and we need to continue to educate the masses about this problem so am right there w/ you Dr. Nancy….I will never stop until every puppy mill is shut down.

    thank you,
    ~jill breitner
    aka Shewhisperer