Wikipedia
Foundation bloodstock or foundation stock are animals that are the progenitors, or foundation, of a new breed (or crossbreed or hybrid), or of a given bloodline within such. Although usually applied to individual animals, a group of animals may be referred to collectively as foundation bloodstock when one distinct population (such a breed or a breed group) provides part of the underlying genetic base for a new distinct population.
The term is particularly common in older breeds for which a written breed registry was not created until after the breed phenotype was well established. However, many modern breeds can be traced to specific, named foundation animals.
The terms for foundation parents differ by sex, most commonly foundation sire for the father, and foundation dam for the mother. Depending upon the species in question, more specialized terms may be used, such as foundation mare for female horses, or foundation queen for female cats. Less common is foundation bitch for female dogs.
The first generation progeny of foundation stock of a hybrid are referred to as F1 hybrid animals, the second generation as F2, and so forth, usually through F4.