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Beef Sire Expected Progeny Differences Calculated by Three Methods¹

Montana State University, Bozeman 59715

Abstract

Data from 20,239 edited field records obtained from the American Simmental Association were used to compare three methods of evaluating beef sires on the basis of AI progeny data for birth and weaning weight. The three methods were the regressed least-squares, contemporary comparison and iterative procedures. Expected progeny difference (EPD) values ranged from 96 to 104 for weaning weight and 92 to 106 for birth weight. Large numbers of progeny are required to evaluate accurately sires in national programs. For this data set the critical number of progeny per sire required to reduce the standard error of the EPD for weaning weight to 2.0 or 1.5 was about 100 or 300, respectively. The degree of association among the evaluating methods based on sire EPD values was high and average product-moment correlations were .91 for least-squares and iterative, .90 for least-squares and contemporary comparison and .96 for iterative and contemporary comparison.

¹ Published with approval of the Director of the Montana Agricultural Experiment Station, Journal Series No. 480.

² American Breeders Service, DeForest, WI 53532.

³ American Simmental Association, 1 Simmental Way, Bozeman, MT 59715.