Methods to Combine Estimated Breeding Values Obtained from Separate Sources
2001
VanRaden, P.M.
Separate estimates of breeding value can be combined using meta-analysis if a combined analysis of all data is not possible or efficient. Computation is fast but not exact if the reliabilities of the separate estimates are approximate, if the extent of overlap of the datasets is unknown, or if selection has occurred across the datasets. Selection index methods were used to combine single-trait evaluations into approximate multitrait evaluations for productive life and to combine singlecountry rankings into multicountry rankings for yield traits. The same methods are used for males and females. To avoid iteration, parent evaluations were included in the data and combined before progeny evaluations. A little information is lost because foreign progeny contribute to domestic parents but not to domestic grandparents. Exchange of sire and dam evaluations provides a closer connection between national and international evaluations and may be more accurate than the current sire-maternal grandsire model used internationally. Correlations of the two evaluation methods were about 0.99 for 35,414 bulls from eight countries. The estimated breeding value of each bull was adjusted separately for information from foreign parents and foreign progeny. Reliabilities of the animal, its sire, and its dam were used to determine how much information came from the parents of the animal versus from its progeny and records. Multitrait reliabilities for productive life were higher than single-trait reliabilities by a mean of 7% for recent bulls and 3% for recent cows. Selection index methods may allow current multitrait across-country evaluations for bulls to be improved and to be extended to cows.
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