I had an interesting conversation with a few colleagues at work today regarding canine litter size. Now, none of the people involved with this conversation appeared to have any expertise in breeding dogs/dog biology. However, their lack of knowledge in this area did not stop strong opinions from forming, again, despite none of them presenting facts to back up their claims. The conversation had to do with the approximate size of adult dogs, and the cause and effect relationship to how adult dog sizes are impacted by the number of puppies birthed to small, versus large litters…or so the argument went. Just to entertain my curiosity, as the conversation itself was interesting and thought-provoking, I figured I would post the question here to see what opinions/facts you all can provide. So here it goes… Regarding puppy litters, does the litter size (the number of puppies birthed) affect the size of the puppy, or how big the dogs will be as adults? For example, take two puppy litters where the sire and dam from each litter are equal (or close to being equal) in weight and height respectively. In this example, one litter produces 4 puppies and the other litter produces 13 puppies. Does the disproportionality in litter size, 4 versus 13 puppies, affect the overall size of the puppies birthed when they reach adulthood? Without other mitigating factors, and only taking into account litter size, is it probable the dogs from the litter that produced 13 puppies will be smaller on average in their adult life, than the adult dogs from the litter that produced 4 puppies? This is Labrador related because I'm expecting to adopt another labrador soon, and this is what started the conversation, as this is the scenario that played out with the breeders I have looked at. From my perspective, I could care either way, the size of the dog is irrelevant. My last labrador Olive was a small girl at 50 pounds, and she was one of the best dogs I could have asked for. I don't think litter size affects the size of dogs when they reach adulthood, but, this is just my opinion. I'm interested to see what others know about this topic.