Milk is reasonably heritable.
Thus, milk production should be the primary selection goal for all dairymen. From an economic standpoint, the selection of other traits should be dependent upon their heritability, economic importance, and phenotypic and genetic relationship to other economically important traits. Profitability is the goal. The rate of progress achieved is dependent upon progress in the population from which the sires and dams are selected by individual dairymen. Genetic and economic aspects of these two sets of alternatives will be discussed later.