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J Dairy Sci. 1991 Aug;74(8):2737-46.

Derivation, calculation, and use of national animal model information.

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Animal Improvement Programs Laboratory, USDA Beltsville, MD 20705-2350.


New terms and definitions were developed to explain national USDA genetic evaluations computed by an animal model. An animal's PTA combines information from its own records and records of all its relatives through a weighted average of 1) average of parents' evaluations, 2) half of its yield deviation, and 3) average across progeny of twice progeny evaluation minus mate's evaluation. Yield deviation is a weighted average of a cow's lactation yields minus solutions for management group, herd-sire, and permanent environmental effects. Bulls do not have yield deviations; however, a weighted adjusted for mates' merit can provide a useful, unregressed measure of daughter performance. Reliability is the squared correlation of predicted and true transmitting ability. An animal's parents, own records, and progeny each contribute amounts of information measured in daughter equivalents. Reliability of USDA evaluations then is computed as (total daughter equivalents)/(total daughter equivalents + 14).

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