Genetic Correlation Extremes in performance for certain traits tend to be associated. An animal that is shorter than average at a given age is also likely to be lighter than average. These associations are known as phenotypic correlations. The association between traits can be caused by environmental factors that affect both traits similarly. For example, availability of food or exposure to disease organisms probably affect both of these traits similarly.
Association resulting from environmental factors is referred to as environmental correlation.
Association between two traits can also be caused by genes that affect both traits simultaneously. This effect results in a genetic correlation. Genetic correlations are of greater importance to the animal breeder. The genetic correlation can be thought of as the correlation between the breeding values of two traits. They indicate the strength of the genetic relationship between two traits.