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

Authors: Keele, John; FORAKER, BLAKE - Washington State University; BOLDT, RYAN - American Simmental Association; KEMP, CHIP - American Simmental Association; Kuehn, Larry; WOERNER, DALE - Texas Tech University

Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/7/2024
Publication Date: N/A
Citation: N/A

Interpretive Summary: Low-cost genotyping platforms and sexed-semen have enabled the production of high breeding value dairy replacement heifers from a fraction of the herd representing the most elite cows. The remainder of the cow herd can be bred to beef bulls using male-sexed-semen. Camera carcass data post-harvest and ultrasound carcass estimates pre-harvest (live animals) on beef x dairy animals combined with genotypes and ultrasound on seedstock animals may provide a lower cost scheme for selecting beef bulls to mate to dairy cows in the future to maximize carcass value of the progeny. Exploiting genotypes to accurately estimate breeding values of candidates based on phenotypes of distant relatives may reduce cost but this depends on how much we can reduce the amount of camera and ultrasound data needed. We report that live animal ultrasound carcass estimates are predictive of post-harvest economically important carcass traits. Accuracy of genetic evaluation of selection candidates without recorded carcass traits were low but are expected to increase with more genotypes and phenotypes on beef x dairy cattle. Genotypes, ultrasound estimates, and camera carcass data on thousands of beef x dairy cattle could enable increased accuracy of selection into the future.

Technical Abstract: Beef × dairy crossbred cattle (n=807) 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=2,440). Five hundred ninety-five of the 807 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 44 traits using 946 bivariate restricted maximum likelihood (REML) analyses. We computed EBV for all 3,247 animals for 4 traits, ultrasound fat thickness at feedlot arrival and re-implanting, and fat thickness and 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. 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. Accuracy (correlation between EBV and true breeding value) for marbling based on 4 trait model ranged from 0.49 to 0.79 for animals with between 2 and 4 phenotypes recorded and from 0.074 to 0.53 for animals without phenotypes recorded. Accuracy of animals without phenotypes was related to the variance in the genomic relationship between animals with phenotype and those without. Overall, the variance in relationship between phenotyped and unphenotyped animals was 0.0012. A subgroup of unphenotyped beef × dairy animals had a variance in relationship with phenotyped animals of 0.0024; whereas the variance was 0.00071 between phenotyped animals and beef × beef seedstock animals. 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.