Genetic correlations in sheep

Selecting for a particular genetic trait may result in changes in other traits. For example, selecting for increased clean fleece weight may result in increased fibre diameter. When this occurs, there is said to be a genetic correlation between the traits, as they are controlled by the same genes or by different genes that are linked.

Genetic correlations between 2 traits can be positive or negative. If the correlation is positive, then there is an improvement in both traits. If the correlation is negative, 1 trait shows improvement while the other deteriorates.

Significance of correlations in selection programs

It is important to look for genetic correlations in order to ensure you maximise the positive traits and minimise the negative one. For example, there is a positive genetic correlation between clean fleece weight and fibre diameter. If selection was based on clean fleece weight alone, fibre diameter would tend to increase gradually.

There is also a positive genetic correlation between clean fleece weight and staple length. Selecting for clean fleece weight will result not only in increased fleece weight but also increased staple length.

Similarly, a negative correlation between wrinkle score and clean fleece weight means that the selection of plainer sheep results in increased clean fleece weight.

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