Interpretive Summary: Evaluation of a genomic-enhanced sorting system for feeder cattle
By: Jackie Walling
Achieving greater carcass uniformity with acceptable yield and quality grade is a goal of cattle production. Genomic characterization using molecular breeding values (MVB) of lean meat yield (LMY) and marbling (MBS) in a process called “marker-assisted management” could be key to increasing uniformity and quality. Identifying MVBs could allow for preselection of cattle producing wanted carcass traits. A recent article published in the March 2019 issue of the Journal of Animal Science evaluated a genomic-enhanced sorting system that utilized predicted MBVs of carcass traits to sort animals towards the desired carcass outcome (70:70 Quality Grid and Y1-LMY).
MBVs of LMY and MBS were chosen as the best markers for improving carcass uniformity and revenue while maintaining beef quality and yield. One thousand one hundred eighteen steers of three different breeds were slaughtered between 2014-2017 for evaluation. The breeds were Kinsella Composite (638), Angus (299), and Charolais (181). Evaluation was done by statistical and computer modeling with MBVs dividing steers into four carcass groups: Quality (MBVs greater than LMY and MBS means), Lean (MBVs greater than LMY mean, less than/equal to MBS mean), Marbling (MBVs greater than MBS mean, less than/equal to LMY mean), and Other (MBV lower than LMY and MBS means).
Results of the sorted MBV groups showed Quality and Lean groups had larger ribeye area and LMY. Quality and Marbling groups showed the most marbling across all three breed populations. Hot carcass weight was similar across MBV groups in Charolais and Kinsella Composite, but not Angus. Genomic-enhanced sorting in this study numerically decreased variability in most carcass traits for Angus and Charolais. Variability slightly increased for Kinsella Composites, indicating more research needs to be done before implementing this method to large scale industry. Concerning the desired outcomes of Quality Grid and Y1-LMY, Angus steers in Quality and Marbling groups met quality grid. Charolais across all MBV groups met Y1-LMY. The results for the purebred breeds suggested further investigation in genomic sorting could be beneficial.
The accuracy of genomic predictions for future carcass outcomes was based on MBV scores of slaughtered steers and resulted in moderately high genomic accuracies. From this result, it was estimated MBV scores could predict 35% of trait variability in carcass outcomes and could assist a genome-based sorting system in making predictions. Predictions were more successful for purebred cattle, but the results encouraged further research to refine MBVs for crossbreds in hopes of implementing genomic sorting systems in large production systems.
For the full article, visit the Journal of Animal Science.