Effects of crossbreeding of native Black and White and Red and White cattle with Holstein Friesian cattle

The active population of Black and White (BW) and Red and White (BW) heifer s and crossbred heifers with Holstein Friesian cattle (HF), were subjected to milk performance control in Poland (1983-1990). It was stated that the y ield of milk and fat was related to the ratio of HF genes In genotypes of t he analysed cows and that the parameters were higher in animals with a high er share df HF genes. In 1990, after 15 years of using the HF breed to impr ove the local cattle population's percentage share of primiparows, cows det ermined to have more than 50% HF blood under performance testing amounted t o 5.09% within the Black-and-White breed and to 0.78% within the Red-And-Wh ite breed.