| Scope and Method of Study: The fatty acid profile and intramuscular expression of genes involved in fatty acid metabolism networks was analyzed between concentrate and forage finishing systems, Angus and Charolais breeds, and glycolytic and oxidative muscle types. First, this study compared intramuscular fatty acid profiles between concentrate and grass finished cattle. A population of 20 animals was selected based on extreme values of the atherogenic index calculated from the fatty acid profile of intramuscular tissue to evaluate intramuscular expression of genes involved in fatty acid metabolism networks. Second, this project analyzed intramuscular fatty acid profiles and gene expression in a population of 12 cattle with either an Angus or Charolais sire. The effect of muscle type on the fatty acid profile and gene expression was also analyzed in samples from semitendinosis and longissimus muscle from each animal in the population.;Findings and Conclusions: Differences in fatty acid profile included a higher atherogenic index, higher percentage total MUFA, lower n-3 to n-6 ratio, lower percentage total PUFA, and lower percentage n-3 fatty acids in CO- compared to FO-finished heifers (P < 0.05). Up-regulation was observed for PPARgamma, FASN, and FABP4 in FO-finished compared to CO-finished heifers in both atherogenic index categories (P < 0.05). Expression of SCD was up-regulated in CO-finished heifers with a LAI, and down-regulated in FO finished heifers with a HAI (P < 0.05). Expression of ADIPOQ was significantly down-regulated in CO-finished heifers with a HAI compared to all other categories (P < 0.05). For the second part of the project, there was a significant muscle type effect for total SFA, MUFA, and PUFA, n-3 (P < 0.05). The LM in both Angus and Charolais sired steers had a higher percentage of total SFA, and a lower percentage of total MUFA and PUFA, n-3 when compared to STN (P < 0.05). For the gene expression data there was a significant sire breed x muscle type interaction for SCD (P < 0.05), and the sire breed x muscle type interaction for PPARgamma and ADIPOQ tended to be significant (P < 0.10). |
