Genetic parameters for carcass traits of progeny of beef bulls mated to dairy cows.

Beef × dairy crossbred cattle (n=615) were used to evaluate the effect of pre-harvest indicator traits and genotypes on accuracy of estimated breeding values (EBV) of seedstock candidates for selection. Genotypes for 100,000 single nucleotide polymorphisms (SNP) were provided by the American Simmental Association of purebred and crossbred seedstock animals (n=2,632). Five hundred ninety-five of the 615 beef x dairy cattle had carcass camera and ultrasound data. Phenotypes were not used for any of the seedstock animals even though some may have had performance and ultrasound data. We estimated the genomic relationship matrix among 3,247 animals including both phenotyped and unphenotyped animals. We computed genetic parameters among 37 traits using 666 bivariate restricted maximum likelihood (REML) analyses. Accuracy of EBV depends on heritability. For the sake of brevity, we report accuracy for marbling as a proxy for other traits with similar heritability. We focus on accuracy for marbling because marbling is the primary determinant of carcass value. We computed EBV for all 3,247 animals for marbling based on camera data post-harvest using best linear unbiased prediction (BLUP). We report evidence of overlap in causative genes among postharvest carcass traits; marbling, ribeye area, yield grade, fat thickness, and hot carcass weight (HCW) based on genetic correlations. Genetic correlations range from -0.73 to 0.89. Several live animal traits (frame size, body weight and ultrasound fat thickness and ribeye area) were genetically correlated with post-harvest traits; including hot carcass weight (HCW), ribeye area, yield grade, fat thickness and marbling. Genetic correlations between pre- and post-harvest traits ranged from -0.53 to 0.95. Accuracy for marbling ranged from 0.64 to 0.80 for animals with marbling recorded, and from 0.09 to 0.60 for animals without marbling recorded. Accuracy of animals without phenotypes was related to the genomic relationship between animals with phenotype and those without. Live animal traits were useful for predicting economically important carcass traits based on genetic correlations. Accuracy of EBV for seedstock animals that were not phenotyped were low, but this is consistent with theory, and accuracy is expected to increase with the addition genotypes and carcass data from beef x dairy animals.