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

Research was carried out on the active population of Black-and-White (BW) a nd Red-and-White (RW) I and heifers crossbred with Holstein Friesian cattle (HF), under milk performance control in Poland (1991-1999). It was observe d that milk, fat and protein yield was related to the ratio of HF genes in the genotypes of the analysed cows and that these parameters increased in r elation to the amount of HF genes that the animals possessed, The predomina nce off-IF genes in BW crossbreeds resulted in a higher fat yield whereas t he content of protein in HF x BW cows and fat and protein content in HF x R W crossbreeds did not evidently correlate with an increased share of BF gen es, Red-and-White cattle transformed into milk producers at a slower rate t han did Black-and-White. After 25 years of using HF breed to improve local cattle populations the percentage of active cows with more than 50% of HF b lood under performance testing in 1999 amounted in 56.0% within Black-and-W hite populations and to 34.8% within Red-and-White breed.