Longissimus Dorsi Muscle Gene Expression in Response to Nutrition:

Identification of Economically Important Genes for Beef Cattle

Objectives: The overall objective is to identify the genes that affect traits such as marbling, tenderness, composition, and palatability in response to plane of nutrition in early weaning production systems.  During the past six years the University of illinois Beef Nutrition group headed by Dan Faulkner and Larry Berger has compiled information on alternative management systems that can increase profit and produce high quality beef (Myers et al., 1999; Wertz et al., 2002; Schoonmaker et al., 2003).  Consumer assessment of beef quality is a major focus for the beef industry, the future of which will depend on the success of producers developing beef cattle that can be produced economically and consistently yield high quality products.  Programs such as value-base marketing offer incentives for cattle feeders and cow-calf producers to raise high-value cattle.  We will use genomic analysis to determine effects of consumption of two isoenergetic diets from early-weaning through 120 days on gene expression profiles in longissimus dorsi muscle. Our hypothesis is that high-energy diets alter gene expression in muscle tissue to different extents as a function of the type of lipogenic precursor (i.e., acetate or propionate) produced during fermentation in the rumen. Therefore, diets will result in marked differences in expression profiles of lipogenic genes and marbling.

Specific objectives are 1) To determine longitudineal global gene expression patterns in L. dorsi tissue in response to different isoenergetic diets, and 2) To relate muscle gene expression profiles with other physiological measurements such as blood hormone concentrations, rates of gain, marbling score, and meat quality.

Potential benefits:  To date we have only begun to scratch the surface in understanding the complex genomic changes during growth, how they are impacted by nutrition and the environment, and their relationship to metabolic and production outcomes. Consequently, we are utilizing the new facilities at the University of Illinois Beef Research Center to develop a comprehensive database that will be valuable for traditional and genomic testing.  The data collected will constitute a rich resource at multiple levels, from gene expression in response to nutrition to detection of QTL influencing growth, carcass, and meat quality in beef.  We will use purebred Angus and Simmental bulls that are widely used in their respective breeds in the project, and are in the top 10 for registrations.  These bulls will represent a large amount of the current genetic material within the breed.  The bulls will be mated to purebred registered cows of both breeds to produce equal numbers of Angus, Simmental and Angus-Simmental crossbred steer calves.  We will collect all standard performance information and process the information through the breed associations.

The future success of the beef industry will be largely determined by our ability to meet consumer demands.  Consumers want beef to be safe, consistently tender, palatable, free of outside fat, easy to prepare, and at a reasonable price compared to other proteins.  The dramatic increase in the number of cattle marketed through grid pricing structures is an example of the beef industry rewarding cattle that meet consumer demands.  Quality and yield grade are the major factors determining price in most grids.  For young cattle, quality grade is determined primarily by marbling, the amount of intramuscular fat in the loin eye.  Yield grade is greatly influenced by the amount of back fat on the carcass.  Developing a system to produce high quality carcasses with minimal trimable subcutaneous fat offers the opportunity for significant economic rewards.