yea it is breeding and genetics as well as with any breed or size of dog. But its known that big dogs have more health problems then little dogs that's all i was saying. bigger dogs usually have more issues because their bodies are so large. Having to maintain a larger body is harder on all parts of the body, like their heart and other organs. There is more strain on their body. Little dogs dont have such a large body to maintain and usually have less issues having to do with their organs and things like that. I use to own bull dogs and oh my god the health problems they had good breeder or not the list was endless.