Even though Although mass selection is a straight forward way of ranking animals as breeding candidates, it is not always the most accurate way. For example, if all we have is own performance, how would we be able to select animals without own performance? How can we select dairy cattle bulls for improved milk production? Or how can we select animals for meat quality? Meat quality can only be measured after slaughter and then those animals cannot be used for breeding anymore. Fortunately there is a solution for that: we use phenotypic information collected on related animals and use that for estimating breeding values for animals without phenotypes. The success will depend on how much their genetics will resemble that of the animal without own performance: their additive genetic relationship.
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