Variability of milk yield, mass fraction of fat and protein in cows of different lines

When increasing the genetic potential of any herd, there is always a question about the origin of cows. The breeding limits for increasing the dairy productivity of cows have not yet been reached, and with the use of a valuable genotype of the Holstein breed, this will certainly happen. Contrary to the genetic theory, according to which hereditary variability should decrease due to selection on a certain basis, the practice of breeding dairy cattle shows that genetic variability increases with increasing productivity. These studies have shown that cows of different lines and generations have a high coefficient of variability in the value of milk yield for the first lactation.