Correlations between Purebred and Crossbred Body Weights in Multi-breed Limousin with Angus Populations

The purpose of this study was to estimate correlations between purebred and crossbredperformance to verify efficiency of current models used in multi-breed selection. Records onthree weight traits: birth weight (BW), weaning weight (WW) and post-weaning gain (PW) frompurebred Limousins (L) and Limousin*Angus progeny (F1), were used to estimate geneticparameters using a multiple trait (purebred and crossbred weights are different traits) approach.For BW there were 148,647 records for L and 17,981 for F1, for WW 81,585 for L and 21,778for F1, and for PW 37,687 for L and 11,021 for F1. Fixed effects in models for L and F1 animalswere contemporary group and month. Random effects for L animals were direct genetic,maternal genetic and maternal permanent environment. Random effects for F1 were sire geneticeffect and dam joint genetic and permanent environment effect. The pedigree for Angus damswas unavailable and therefore these dams were assumed unrelated. The direct h estimates forpurebred animals were 0.35, 0.25 and 0.31 for BW, WW and PG respectively. ForF1, the sameestimates were 0.25, 0.38 and 0.34. Genetic correlations estimates between purebreds andcrossbreds were 0.4, 0.6 and 0.3 for BW, WW and PG respectively. The results indicate cthatpurebred selection is only partially effective on crossbreds; in particular, sires may bemisevaluated for BW and PG. Even though the correlation is lower than unity for WW (0.6), selection in purebred populations may still be very effective in this trait due to a higherheritability in crossbred animals than purebred animals. Estimates in this study may be biased bythe ignoring of maternal pedigrees inF1.