sources of variability of growth and body development traits of simmental bulls in performance test

To test the variability of traits of Simmental bulls in performance test, data of the Livestock - Veterinary Centres for Reproduction and Artificial Insemination of Velika Plana and Krnjača were used. In the analysis, data on 113 performance tested bulls born from 2008 to 2009 were used. The analysis included two sets of characteristics: body development traits and growth traits. The average body mass of calves entering the test was 195.75 kg, while the body mass at the end of the test was 476.50 kg, average daily gain in the test was 1138.69 g. Average values of body development traits measured at the end of the test, with 12 months of age were: height at withers 127.13 cm, chest circumference 179.42 cm, the chest depth 61.19 cm and body length 151.34 cm. The influence of their sires, the year and the Centre on the variability of traits was studied. The effect of age is present at a high level of statistical significance (p<0.01) for all traits that are registered at the end of the test, while the effect of the Centre was present in the variability of body mass at the end of the test, the daily gain in the test and the length of the body. The bulls-sires' influence was demonstrated (p<0.05) on the variability in body mass of calves entering the test.