Bovine intramuscular gene expression and fatty acid profiles were characterized in concentrate and forage based beef finishing systems. Intramuscular samples were obtained from 99 heifers finished on concentrate (CO) and 58 heifers finished on forage (FO). Fatty acid profiles from IM samples were obtained using gas chromatography and animals were ranked based on the atherogenic index (AI). Twenty heifers with either a high (n=10, HAI) or low (n=10, LAI) AI were selected for gene expression analysis. Total RNA was extracted from intramuscular samples and gene expression (n=10) was quantified using SYBR Green real-time PCR. Delta CT (threshold cycle) values were analyzed for differences within each diet and AI category. Atherogenic index comparisons within each diet identified significant (P<0.05) down-regulation of adiponectin (ADIPOQ) in CO finished heifers with a HAI. Significant (P<0.05) up regulation of diglycerol acyl-transferase (DGAT) was also observed in FO finished heifers with a LAI profile. Comparison between diets within each AI category identified significant (P<0.05) up-regulation of fatty acid synthase (FASN), fatty acid binding protein 4 (FABP4), and peroxisome proliferator activated receptor gamma (PPARγ) in FO fed heifers with a LAI profile compared to heifers with a HAI profile. Comparisons between AI categories within each diet also identified significant (P<0.05) up-regulation of DGAT, FASN, FABP4, PPARγ, and ADIPOQ in heifers with a HAI that were finished on FO. These results suggest ADIPOQ and DGAT are likely involved in intramuscular fatty acid saturation and that significant dietary interactions with gene expression play a significant role in lipogenesis.
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