Genetic evaluation of the scrotal circumference of beef bulls in the Czech Republic

The objective of the present study was to estimate the genetic parameters for the scrotal circumference of bulls of beef breeds in the Czech Republic. The used database for the years 1996–2020 comprised information on the scrotal circumference measurements from 22 065 bulls of 19 pure breeds and crossbred animals of the Beef Simmental, Charolais, and Hereford breeds. After adjustments, the database contained 16 404 records. To test the influence of systematic fixed effects, the GLM/SAS procedure using the least-squares method was applied. The contemporary group, weight and age of the bulls were included as significant systematic environmental effects (< 0.05). The genetic parameters were determined by a single-trait model using the AIREMLF90 program. The heritability coefficient of the scrotal circumference was 0.27. Environmental correlations of the scrotal circumference with the bull weight were moderate and positive (r = 0.2), but the correlations between the age in days and the scrotal circumference were almost zero (r = 0.03). The results indicate that the scrotal circumference of beef cattle breeds provides sufficiently high genetic variability that can be used to identify individuals with an above-average circumference and, in this way, increase the probability of selection of a young bull with a better reproduction potential.