Accuracy of Genetic Indexes of Cows from Adding Relatives

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Abstract
A cow index including data on the cow, her sire, dam and maternal grandsire was correlated more (8%) with son''s progeny test in Holsteins than was an index from the cow and her sire. The 4 other breeds showed increases with added data. The 4-source index showed little or no advantage over the 2-source index in predicting daughter performance. Part of that result may be attributed to an environmental correlation between cows and their daughters. Cow data were more important than expected and sire data less important than expected in predicting daughter performance. The reverse was true in predicting son''s progeny test. SD of indexes with 4 sources of information were 7.6-11.6% higher than those of indexes from the cow and her sire. Correlations between the 2-source index and change in index from 2 to 4 sources were 0.05-0.17. A direct approach to computing weights for use in the four-source index required 5% of the computing time of an approach that required inversion of a matrix of order three. Both approaches took advantage of the combined dam and maternal grandsire data in the dam''s index.