Investigation of the heritability of phenotypes of fertility and milk performance of Simmental cattle breed in Serbia
Results of the effect of direct and indirect selection of quantitative traits of fertility and milk performance of first calving cows of Simmental breed in Serbia are presented. Investigation of genetic parameters of heritability (additive genetic variance in total phenotypic variability of quantitative traits) and analysis of milk traits was done in four breeding regions and several tenths of farms where 3980 daughters of 32 sires were housed and reared. Results of analysis were obtained by application of mathematical-statistical data analysis, using mixed models (Harvey, 1990). Mathematical-statistical analysis of data was done using linear methods, i.e. method of least squares (LS method). Based on obtained results it was established that bulls-sires and several paragenetic factors caused no significant variation of fertility traits in relation to general average (P<0.01). Quantitative milk traits of first calving cows, under the influence of breeding region, had significantly higher deviation from the general average (**P<0.01). Significant deviations (*P<0.05) were caused by year of calving on milk yield and yield of milk fat (4765.0 kg and milk fat 3.86%). Established heritability coefficients for reproductive traits were following: .102, .051 and .088, and milk traits .297, .207 and .197).