There are many things we would like to include in a breeding program to create the most desirable cow. However, there are three important questions we must ask about each trait. There must be genetic differences among those animals available for selection. We must be sure that the total merit is improved, that adding an additional trait does not slow us in our pursuit of the ideal.
Genetic correlations measure the tendency for traits to be inherited together.
A positive correlation indicates improvement in both traits at the same time, whereas a negative correlation indicates that as one trait improves, the other trait declines. Traits which are not related have a zero correlation. Milk Components Milk components have positive and negative genetic correlations as shown in Table 1. By measuring their relationships, one can determine the amount of genetic progress possible and which program will maximize income for the dairyman. All yield traits show relatively high, positive correlations.