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Comparison of Beef Sire Evaluation Models for an Organized Progeny Test¹

University of Guelph², Guelph, Canada N1G 2W1

Abstract

Sire evaluation models were compared using progeny records of 73 Simmental sires for gestation length, birth weight, calving ease, gain on dam, 200-d weight, gain on test (GT) and 365-d weight (YW). Mixed model techniques were used to obtain sire estimated transmitting abilities (ETA). The models contained combinations of the fixed effects: herd-year (HY), breed of dam by age of dam by sex of calf (BAX) and sire genetic groups Gl and G2, grouped by year of test or birth, respectively. Random factors were sire and residual with additive genetic relationships among sires and maternal grandsires involved in some models. Two special fixed effects, herd-year by sex of calf (HYX) and breed of dam by age of dam (BA) were applied to GT and YW only. Coefficients of determination (CD) were constant across all models for each trait, except for GT and YW, where models utilizing HYX and BA had higher values. Pearson (RP) and Spearman Rank (RS) correlation coefficients of ETA were computed between models. Grouping strategy affected RP and RS values. The RP and RS between models that did not include Gl were >.92 and between models that did include Gl were >.96. The RP and RS between models including and not including Gl were >.76. Including group effects in the models increased standard errors of prediction (SEP) of sire ETA by 7 to 53% over a model without groups. Including relationships among sires and maternal grandsires in the model reduced SEP values of ETA by 1.5% on average. Therefore, the model used to analyze all traits except GT and YW included HY, BAX, sire and residual, as well as additive genetic relationships among sires and maternal grandsires. Traits GT and YW were analyzed using a model that included HYX, BA, sire and residual plus additive genetic relationships among sires and maternal grandsires.

¹ Data supplied by Canadian Simmental Assoc, and financial assistance supplied by the Natural Sciences and Engineering Research Council of Canada and the Ontario Assoc, of Animal Breeders are gratefully acknowledged.

² Dept. of Anim. and Poul. Sci.