Crossbreeding

Crossbred dogs are the product of mating's between two animals of different breeds. They should not be confused with mongrels, which are the product of mating’s between dogs of unknown breeding.

When, in 1814, Princess Charlotte invited Charlie Aistrop to mate his terrier, Billy (famous for having killed 100 rats in five and a half minutes), to one of her tricolour Toy Spaniels she probably did so not because she intended to compete in the rat pits, but simply because she realized that her dogs required an infusion of vigorous blood.
Eskimos indulge in precisely the same practice when they contrive to get their sledge-dog bitches mated by wolves.
The breeders of some unrecognised breeds make regular use of crossbreeding in order to improve the qualities of their breed. There is no doubt that, in Britain white working Lakeland Terriers were used to overcome the hereditary problems which beset stumpy-legged Jack Russell Terriers, to impart quality and smartness and to bring them up on the leg. Breeders of unrecognised Jack Russell Terriers retain the freedom to indulge in cross-breeding. Breeders of recognized Parson Jack Russell Terriers can no longer avail themselves of the advantages it might have to offer. The vigour of recently recognized breeds provides evidence of the value of the wise use of crossbreeding.
These crosses will make it easier for the breeds to retain genetic health after recognition, which places a severe restriction on the size of the available breeding population and will call for a very different system of breeding management if the breeds are henceforth to survive in a healthy state.
Official recognition as a breed need not end the ability to indulge in judicious crossbreeding. In the UK, the Kennel Club has allowed it between Bull Terriers and the miniature version; between the Long- and Short-Coated Chihuahuas and more recently, has gone to the extent of amalgamating the four Belgian Shepherd Dog Breeds in order to facilitate cross-breeding between Malinois, Tervueren, Groenendael and Laekenoise, to which the majority of breeders are vehemently opposed. However, it must be accepted that these are the rare exceptions to the general rule. Official recognition usually ends or at best makes it more difficult to make use of crossbreeding.
The Lurcher is probably unique in that it is a breed that exists, and has existed, for hundreds of years on the basis of crossbreeding. Breeders make use of Greyhounds, Whippets and Salukis as the source of speed and chasing ability; they use various collies and other working breeds to impart intelligence; and terriers of various sorts, to give a dash of fire to the mixture. The result is a sound, intelligent and uniquely resourceful dog which comes in a variety of sizes and shapes, all of which are undoubtly Lurchers.
The value of crossbreeding is utilized by farmers who often cross two pedigree animals: Cheviot ewes to Suffolk rams, Charolais bulls to Friesian cows, in order to produce crossbred offspring (know as F1 cross) which, as a result of the hybrid vigour or heterosis which frequently occurs in the first (F1) generation of such crosses, will thrive better that either of their parents. Hybrid vigour seldom persists into the second (F2) generation (produced by mating two F1 hybrids), and is absent from the product of subsequent generations. Hybrid vigour is entirely the product of mating between totally unrelated pure-bred animals, not mongrels. It is a quality which can be maintained by a carefully controlled out breeding programme.