Abstract
The research presents the comparative characteristics of the cows’ lactation performance and biological efficiency of milk production of the cows of different lines, bred in the farms of the North-West region of Russia and Northern Kazakhstan. Due to the wide use of the Holstein genotype in order to improve the milk production of the black-and-white cattle it is recommended to assess not only the quantitative and qualitative indicators of the productivity of cows, but also the biological efficiency of the milk production. It allows evaluating the genetic potential of the animals more sufficiently and recommending the animal units of the best lines for wide use in such conditions. Based on the research findings the most productive lines for the different geographic regions and economic conditions were identified.