The performed semi-intensive fattening the Red-White bulls with different share of the HF blood /25, 50, 62,5 and 75%/ showed that the crossbreds with more than 50% HF had higher body measurements but worse indices of body conformation, in comparison with the Red-White bulls. The highest body weights at 18 months of age had the crossbreds F₁ - 499,7 kg as well as the highest daily weight gains - 936 g. The group of F₁ crossbreds was the most effective in feed conversion. The animals in this group used 6,9 oat units, 695 g total digestible protein and 7,53 kg dry matter per 1 kg of body weight gain.
The analysis was performed on 754 Polish black-and-white sires bom in the period 1970 - 1980. Three age categories (1 year, 3 and 5 years) were considered. Hertability coefficients, genetic and phenotypic correlations were calculated according to the Harveys model Genetic and phenotypic correlations between body weight and the most commonly used body measurements were calculated between the sires aging 1 year and 3 years, 1 year and 5 years, 3 years and 5 years. Low heritability roefficiens occurred in case of body weight and in most body measurements at the age of 1 year, excluding sacrum height (h²=0,66) and width of forechest (h²=0,68). Value of heritability coefficients increased significantly at the age of 3 and 5 years. No significant correlation between body weight at the age of 1 year and 3 years and 1 year and 5 years has been found. Correlation between the same body measurements performed in these periods was also low. High genetic and phenotypic correlations of the body weight and the body measurements at the age of 3 and 5 years have been proved. Results of this study suggest that selection for performance traits should take place when sires reach the age of 3 years.