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Interim Expected Progeny Differences for Young Animals Not Included in National Cattle Evaluations^1,2,

Iowa State University, Ames 50011

Abstract

A procedure was tested that would enable beef cattle breed associations to compute interim expected progeny differences (EPD) for direct growth traits of young animals not included in the most recent national cattle evaluation (NCE). The procedure estimated contemporary group (CG) fixed effects of young animals just measured by adjusting records of young animals for the predicted breeding values of their parents obtained from the last NCE, if available, and then by obtaining a weighted average of adjusted records. The weighting was governed by whether or not the EPD of the parents were available from the last NCE. The difference between the performance record of an animal and the CG estimate was used to obtain a prediction of effect due to Mendelian sampling for that animal. Interim EPD were computed as half the sum of the EPD of sire and dam for each trait of interest plus half the effect due to Mendelian sampling of the animal. Interim EPD were computed sequentially by CG, allowing records to be processed by the associations upon receipt from breeders. To test the procedure, rank correlations were computed between interim EPD of young animals and their EPD from the NCE of 1986. Rank correlations between interim EPD and EPD from the NCE of 1986 for young animals with EPD available from the NCE of 1985 for both parents were .93, .93 and .96 for birth, direct weaning and yearling weights, respectively. For young animals with only the EPD of sire available from the NCE of 1985, rank correlations between interim and actual EPD were .83, .84 and .82 for birth, direct weaning and yearling weights, respectively.

¹ Journal paper no. J-12624 of the Iowa Agric. and Home Econ. Exp. Sta., Ames, project no. 2000. This research was funded in part by a grant from the American Angus Assoc., St. Joseph, MO.

² Authors gratefully acknowledge the help of American Angus Assoc. and Larry Benyshek and Del Little, Univ. of Georgia, in assembling data used in this project.