ANALYSIS OF FACTORS INFLUENCING THE DEVELOPMENT OF ECONOMIC CHARACTERS OF DAIRY CATTLE OF DIFFERENT ORIGIN
The development of quantitative economic characters of dairy cattle is influenced by a complex of factors of genetic and non-genetic nature, as well as the peculiarities of their interactions. The extent and probability of such influence is specific to each farm, genotype of animals, breed and region of use, which necessitates a detailed analysis of each separate case in order to plan the breeding activities properly. The differences between separate herds are caused by the peculiarities of technological conditions of production, the size of the herd, geographical and climatic conditions of the farm. The factors of the year and season of calving are influenced mainly by the feeding conditions during the year and over several production years. Those factors account for the variability of selection traits and are associated with the climatic conditions over a particular period. The research revealed that there was significant influence of the «father/mother’s father» genetic factor on the basic selection traits. The power of influence of the «animal’s father» factor was 5.0% for milk yield, 5.3% for milk fat content, 23.3% for the age of first calving, and 3.4% for the number of inseminations per one fertilization. The interactions between the environmental factors significantly influenced the variability of all traits with the power of influence ranging from 5.3% for the service period up to 37.1% for the age of first calving. Also there was a clear trend of improvements in the technological conditions of the enterprises from 1993 to 2011. The effect of influence of such factor as the particular year of calving was gradually increasing from negative values and reached the value of +3007 kg by 2011.