COMPARISON OF SIRE BREED SOLUTIONS FOR GROWTH TRAITS ADJUSTED BY MEANEXPECTED PROGENY DIFFERENCES TO A 1993 BASE

Records on growth traits were obtained from five Midwestern agricultur al experiment stations as part of a beef cattle crossbreeding project (NC-196). Records on birth weight (BWT, n = 3,490), weaning weight (WW T, n = 3,237), and yearling weight (YWT, n = 1,372) were analyzed with in locations and pooled across locations to obtain estimates of breed of sire differences. Solutions for breed of sire differences were adju sted to the common base year of 1993. Then, factors to use with within -breed expected progeny differences (EPD) to obtain across-breed EPD w ere calculated. These factors were compared with factors obtained from similar analyses of records from the U. S. Meat Animal Research Cente r (MARC). Progeny of Brahman sires mated to Bos taurus cows were heavi est at birth and among the lightest at weaning. Simmental and Gelbvieh sires produced the heaviest progeny at weaning. Estimates of heritabi lity pooled across locations were .34, .19, and .07 for BWT, WWT, and YWT, respectively. Regression coefficients of progeny performance on E PD of sire were 1.25 +/- .09, .98 +/- .13, and .62 +/- .18 for BWT, WW T, and YWT, respectively. Rankings of breeds of sire generally did not change when adjusted for sire sampling. Rankings were generally simil ar to those previously reported for MARC data, except for Limousin and Charolais sires, which ranked lower for BWT and WWT at NC-196 locatio ns than at MARC. Adjustment factors used to obtain across-breed EPD we re largest for Brahman for BWT and for Gelbvieh for WWT. The data for YWT allow only comparison of Angus with Simmental and of Gelbvieh with Limousin.