Genetic Aspects of Marbling in Beef Carcasses

INTRODUCTION: The goal of this paper is to review the genetic aspects of marbling in beef carcasses and to serve as a reference source. It is not meant to be an exhaustive review of the literature in regard to all relationships involving marbling with other production and carcass traits. However, it is meant to review several of the major studies around the world that could have direct genetic implications on production of beef carcasses in the United States. Historically, fat thickness of fed cattle has been used to estimate carcass quality grade. As a result, this paper focuses on the relationship between subcutaneous fat thickness and marbling. Following an Executive Summary of points, the paper is organized into sections of (1) breed comparison studies, (2) estimates of genetic variation, heritability and correlations of marbling and other carcass traits, (3) evaluation at different carcass end-points, (5) single gene and genetic marker considerations, (6) impacts of selection on marbling, (7) National Beef Quality Audit aspects, and finally (8) cowherd considerations.