A Procedure for Including the Dam and Maternal Grandsire in USDA-DHIA Cow Indexes

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Abstract
The United States Department of Agriculture Dairy Herd Improvement Association Cow Index currently uses data from only the cow and her sire. The suggested procedure also will include data from the dam and maternal grandsire. Substituting the dam''s Cow Index for the dam and maternal grandsire data is equivalent to a 4-source Cow Index. The procedure provides necessary weights for the 4 sources by one simple calculation of a weight rather than by inversion of a matrix. These efficiencies of calculation permit economical calculations of more accurate Cow Indexes.

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