BREED COMPARISONS FOR GROWTH TRAITS ADJUSTED FOR WITHIN-BREED GENETICTREND USING EXPECTED PROGENY DIFFERENCES

Records (2,910) of birth (BWT), weaning (WW), and yearling weight (YW) of F1 calves produced in a top-cross experiment involving Angus, Here ford, Pooled Hereford, Charolais, Limousin, Simmental, Gelbvieh, Maine -Anjou, Chianina, Tarentaise, Shorthorn, and Salers bulls mated to Her eford and Angus cows and records (4, 592) of WW on three-breed-cross c alves out of 986 F1 females of the same breed crosses were used in thi s study. The purposes were to estimate how much of the EPD of the sire s was realized in crossbred calves and to estimate sire breed effects for the traits adjusted for genetic trend and sire sampling. Published EPD for BWT, WW, YW, net maternal ability (MLK), and maternal WW (MAT ) were used. Average regressions (kilograms/kilogram +/- SE) of BWT, W W, and YW of F1 calves on EPD of the sire were 1.04 +/- .10, .88 +/- . 11, and 1.40 +/- .11, respectively. The regressions (b, kilograms/kilo gram) were similar to the expected values of 1.0 except for YW. For WW of three-way-cross calves on MLK EPD of the maternal grandsire, b was 1.02 +/- .11, which was not different from the expected value of 1.0. Estimated sire-breed means were adjusted to a 1982 genetic base by ad ding b times the difference of the 1982-breed-mean EPD and mean EPD of sires used in the study. Three different adjustments were compared us ing the b pooled across breeds, a separate b for each breed, and the e xpected b of 1.0. In general, the adjustments tended to regress breed of sire means toward the average of all breeds, particularly for BWT a nd WW of F1 calves, and for WW of three-breed crosses. The effect of t ype of adjustment varied among breeds, but in most cases small differe nces resulted from using average or expected b. For WW, the range for net maternal effects among breeds was larger than that for direct bree d effects.