Genetic parameters of the traits recorded in the performance test of dual-purpose bulls

The data on 1 144 performance tested Czech Pied bulls born from 1991 to 1997 were analysed. The test started at 111 days of bulls' age and lasted until the age of 420 days. Simulation analysis was carried out for the age of bulls at the end of the test 210, 300, 330, 365, and 420 days. Genetic parameters were estimated for different test periods and the relationships between the periods were analysed. The heritability coefficients for live weights of young bulls recorded at different age ranged from h(2) = 0.20 to h(2) = 0.46. For average daily gains in different periods according to the simulated termination of the test, the estimated heritability coefficients ranged from h = 0.20 to h(2) = 0.59. The genetic correlations between the test termination at 300 days of age and the termination at 330, 365 or 420 days ranged from r(g) = 0.88 to r(g) = 0.99 for live weight and from r(g) = 0.61 to r(g) = 0.91 for average daily gain. These results support the idea to reduce considerably the duration of performance test in young bulls.