The impact of breeding region and lactation on milk yield traits in the of Simmental cattle population of the Republic of Serbia

The objective of this research was to study phenotypic expression and factors that can affect milk yield traits in the population of Simmental cattle breed in the Republic of Serbia. The research was conducted on a set of data that included records on the production and origin of Simmental breed cows displayed both in regional and municipal exhibitions in the territory of the Republic of Serbia in the period from 2004 to 2017. A final data set included records on production and origin of 1176 Simmental breed cows. The animals were raised in the area covering 9 regions of the Republic of Serbia. The research included most important milk yield traits in standard lactation: milk yield, milk fat content, milk fat yield, yield of 4% fat corrected milk (4%FCM). An average milk yield in studied population accounted for 5.520±919 kg, milk fat content 3.94±0.11%, milk fat yield 218±38 kg, while the yield of 4% fat-corrected milk accounted for 5.474±933 kg. It was determined that region, age and lactation had a very high statistically significant effect on studied traits while the age of cows had no statistical effect