Evaluation of molecular mechanisms impacting beef quality and carcass characteristics

Abstract

Tenderness has been stated as being one of the most important traits for consumers with regards to purchasing steak. However, too often there is much variation in tenderness in steaks that grade the same quality. Research in the past has done little to expand on the impact that genetics has on meat tenderness. This study was designed to attempt to illuminate this question by looking at the genes being differentially expressed between quality grades, and the pathways they impact. Angus crossbred steers (15) were fed to the end points of Standard, Select and Choice. Intermuscular and subcutaneous adipose tissue and muscle samples were snap frozen for gene expression analysis, as well as a loin kept from each animal for shear force analysis. Shear force analysis showed a significant difference between Choice and Standard graded animals (P<0.05), showing that the Choice animals in this study were more tender than Standard. RNA extracted from the adipose and muscle samples were sent to Novogene for RNAseq analysis. The results of the gene expression analysis showed 4 genes down regulated and 29 up regulated in the comparison of Select to Standard adipose tissue, with 8 genes down regulated and 15 up regulated with Select to Choice adipose tissue. The largest difference occurred between Standard to Choice adipose tissue with 49 genes down regulated and 113 up regulated. With regards to the muscle, 15 genes were down regulated while 20 were up regulated in the Standard to Choice. In the Select to Choice, 1 gene was down regulated with 4 up regulated. When comparing Select to Standard, there was not a large enough difference in genes being expressed. This study emphasized the need for additional functional studies on the impacts of gene expression on marbling deposition.