Purebred dogs are only bred to others of their breed so that the puppies can be registered as purebreds. Dog breeders take great pride in planning their offspring carefully so that they represent the very finest specimen of the breed. Defined physical traits called “points of conformation” are used to judge dogs in shows, and the champions are in high demand for breeding programs to make the next generation of pups the very best. All of this hard work means that these pups cost more to buy than a mutt. It also means the chances of a purebred dog mating with another breed are slim if the dogs remain under control.
Implications of Crossbreeding
If a male dog breaks free and roams he might mate with a female dog of another breed. If there is a significant mismatch in size between the two dogs there can be problems during the birthing process. This is because if the father dog is much larger than the female, she may have trouble pushing out the over-sized pups. The father will contribute genes that tend to make the offspring his size, and the mother dog will contribute genes that code for a puppy of her size, so likely the pups’ size will be in-between (on average). If a much smaller male dog breeds with a larger female, the puppies will tend to be smaller than usual, so birthing difficulty is much less likely.
The mixing of genes from two breeds will also mean that the puppies will tend not to look like purebreds. The mixing may produce a dog that has face shape, body and leg size, and shape and haircoat that look a bit like both breeds. Sometimes a trait will be expressed completely from one parent, and another trait will show up that is given by the other parent. The puppies cannot be registered as a particular breed despite the fact that some pups may appear to be purebred.