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Title: ADJUSTMENT FOR HETEROGENEOUS GENETIC AND NON-GENETIC (CO)VARIANCE STRUCTURES ON TEST-DAY MODELS USING A TRANSFORMATION ON RANDOM REGRESSION EFFECT REGRESSORS

Author
item GENGLER, N - GEMBLOUX AGRIC UNIV
item WIGGANS, GEORGE

Submitted to: Interbull Annual Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 5/26/2002
Publication Date: N/A
Citation: N/A

Interpretive Summary: A method of accounting for differences in variation in components of test-day milk production records was developed. This method could improve the accuracy of genetic evaluations. A random regression model is used to analyze the data, then a transformation is applied to the random regression coefficients. Comparing evaluations with and without this transformation, rankings of animals were similar but some rerankings occurred. A correlation analysis showed a reduction in the effect of production level on the variation in regression coefficients indicating the success of the ransformation. The method suggests a number of innovative solutions to problems related to heterogeneous variance structures.

Technical Abstract: A method of accounting for differences in variation in components of test-day milk production records was developed. This method could improve the accuracy of genetic evaluations. A random regression model is used to analyze the data, then a transformation is applied to the random regression coefficients. Comparing evaluations with and without this transformation, rankings of animals were similar but some re-rankings occurred. A correlation analysis showed a reduction in the effect of production level on the variation in regression coefficients indicating the success of the transformation. The method suggests a number of innovative solutions to problems related to heterogeneous variance structures.