Relationship of Beef Sire Birth Weight and Weaning Weight Expected Progeny Differences to Actual Performance of Crossbred Offspring

Performance records from 1982 to 1992 on 1365 calves for birth weight (BW) and 1492 calves for weaning weight (WW) were analyzed to estimate relationships of purebred sire expected progeny difference (EPD) values for BW and W W to actual crossbred progeny performance. Sires of the calves were Polled Hereford, Simmental, Angus, Salers, Tarentaise, or Charolais. The pooled-across-breed regressions (Ib/lb + SE) of BW and WW of calves on sire EPD were 1 .I 7 * .31 and .75 + .28, respectively. Residual correlations of BW with BW EPD and W W with WW EPD were . I 6 (P< -01) and .05 (P= . lo), respectively. Additional regression and residual correlation analyses were conducted in which records from progeny of low-accuracy sires (Acc. < .50) were deleted. The reduced data set included 967 records for BW and 962 records for WW. The pooled-across-breed regressions (Ib/lb + SE) of BW and W W of calves on higher-accuracy sire EPD were 1.28 + .35 and .71 * .31, respectively. Residual correlations using higheraccuracy sire data of BW with BW EPD and W W with W W EPD were . I 8 (P<.01) and .09 (P = .02). Breeders who use BW and W W EPDs as a selection tool should expect such selection t o be effective, on average, and reasonably consistent w i th theoretical expectation. However, some sires and small progeny groups may not rank as expected based on sire EPDs.