Investigations were carried out on 2118 performance-tested yearling bulls kept in four rearing stations in the period 1983 - 1987. Influence of genotype, year of birth and intraction: year of birth x genotype, on body weight, height at withers and heart girth were studied. Within the six different genotypes the highest body weight at the age of 360 days was obtained by Polish x British Friesian bulls (450,6 kg). The best value for height at withers was reached by Polish x Holstein Friesian (HF) crossbreds (121,5 cm) and for heart girth by Polish x British Friesian crossbreds (179,2 cm). The lowest records of above traits were recorded in Polish black-and-white and Polish black-and-white x New Zealand crossbreds. Within Polish black-and-white x Holstein Friesian crossbreds 7 groups, according to percentage of HF blood, were analysed. Height at withers was significantly influenced by percentage of Friesian blood and incrased from 119,8 cm in the group of 6,25 - 12,5% HF to 124,2 cm in the group over 75% of HF. A linear correlation was found between percent of HF blood and body weight and heart girth. The highest body weight was found in bulls of 53 - 68% HF (440,9 kg) and the highest heart girth in 6,25 - 12,5 HF (178,1 cm).
Influence of rearing station, birth year and interaction station x year on body weight and 4 measurments were studient on the population of 4665 yearling bulls reared in 4 performance testing station in tbe period 1972 - 1987. Body weight and body measurments were dependent much more on station than on year of birth. Interaction station x year of birth was significant Magnitude of changes in the body weight and measurements were relatively low in the period of 16 years indicating that body conformation of pure-breed Polish black-and-white yearling bulls underwent no significant changes.