Relationship between a bull's parental genetic merit difference and subsequent progeny trait variability in Angus, Gelbvieh, and Limousin cattle

Data from the American Angus Association, American Gelbvieh Association, an d the North American Limousin Foundation were analyzed to determine whether parental genetic differences are associated with Mendelian sampling of the ir bull progeny or with Mendelian sampling variances and weight variances o f their bull progeny's offspring. Parental differences were measured as the difference between the parents' EPD for birth weight (DIFBW), weaning weig ht direct (DIFWW), and yearling weight (DIFYW). A bull's data were used if both parents had calculated EPD and the bull had at least 25 progeny with r ecords for the specific trait. Traits calculated for each bull were his Men delian sampling (MSBull), progeny Mendelian sampling variance (MS sigma(pro geny)(2)), progeny weight variance (WT sigma(2)), and progeny corrected wei ght variance (CWT sigma(2) adjusted weight minus appropriate dam EPD) for b irth, weaning, and yearling weights. Pearson correlations were computed bet ween DIFBW, DIFWW, and DIFYW and MSBull, MS sigma(progeny)(2), WT sigma(2), and CWT sigma(2) for each trait, within each breed. Across breeds, the cor relations ranged from -.07 to .11 for MSBull, .01 to .14 for MS sigma(proge ny)(2), -.06 to .09 for WT sigma(2), and -.06 to .08 for CWT sigma(2). Alth ough some of the correlations were significantly different from zero their relatively small magnitude indicates little relationship between parental d ifferences in genetic merit and subsequent offspring variability for each o f the three breeds.