Abstract #W220

# W220
Muscle gene expression patterns in finishing steers supplemented with dietary Amaize (Aspergillus oryzae extract).
Daniel E. Graugnard*1, Kristen M. Brennan1, Allison C. Smith1, Sonia J. Moisá2, Juan J. Loor2, 1Alltech Center for Animal Nutrigenomics and Applied Animal Nutrition, Nicholasville, KY, 2Department of Animal Sciences, University of Illinois, Urbana, IL.

We evaluated the effect of dietary Aspergillus oryzae extract on gene expression profiles in the Longissimus lumborum from finishing steers. Cross-bred (Simmental × Angus) yearling steers were randomly assigned to one of 2 groups (n = 10/treatment). From receiving until d21, starter and step-up diets were fed to acclimate steers to a traditional mid-west finishing diet. Steers were then fed ad libitum to meet or exceed NRC requirements until slaughter (d140): basal diet with or without 5 g/hd/d of A. oryzae extract (Amaize, Alltech Inc., Nicholasville, KY) containing α-amylase (AMZ). On d90, Longissimus lumborum tissue was collected for gene expression analysis. Serum was collected at d 40, 90 and 140 for analysis of metabolites (BHBA, glucose, insulin, urea). Data from blood metabolites was analyzed using a mixed model. Gene expression was profiled using the Affymetrix Bovine Gene 1.0 ST Array. Performance did not differ between treatments. Hierarchical clustering indicated a treatment effect (P < 0.05) of the AMZ-supplemented group compared with the control. A total of 1148 genes were differentially affected (P < 0.05; 430 upregulated; 718 downregulated) between treatments. The genes affected, enriched (P < 0.05) and activated several pathways, including IGF-1 signaling, insulin receptor signaling, valine degradation, and VDR/RXR activation. The pathways activated are involved in the regulation of muscle development and growth. Blood metabolites indicated greater levels of BHBA, urea and insulin (P < 0.05) at d40 in AMZ-supplemented steers. Only insulin remained at a greater concentration in the AMZ group than the control throughout the experiment. In conclusion, AMZ supplementation in the finishing diet affects muscle gene expression and insulin metabolisms, potentially causing a positive effect for the development of skeletal muscle in finishing steers.

Key Words: amylase, muscle, cattle