Post-mortem oxidative status and gene expression of antioxidant enzymes in <i>longissimus thoracis et lumborum</i> muscle of Braford steers with different feeding systems

Meat is highly susceptible to oxidation, which leads to the degradation of lipids and proteins, resulting in undesirable changes in meat quality, such as colour and shelf life. This process can be mitigated by both non-enzymatic antioxidants and enzymatic antioxidants, including superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx). The oxidative stability of meat is influenced by several factors, including animal nutrition. The aim of this study was to assess the impact of corn silage supplementation on meat oxidative status and its correlation with the expression level of genes associated with this process in the <i>longissimus thoracis et lumborum</i> muscle of Braford steers. For this study, 30 steers were randomly assigned to two experimental groups of 15 animals each. One group was fed with <i>ad libitum</i> pasture supplemented with corn silage and the other group was fed with <i>ad libitum</i> pasture. The degree of protein and lipid oxidation was determined by total protein carbonyl content and lipid degradation products, respectively. The antioxidant capacity was determined by measuring the radical-scavenging activities, total phenol content (TPC), and the activities of the CAT, SOD, and GPx enzymes. In addition, the relative levels of <i>sod</i> (1 and 2), <i>cat</i>, and <i>gpx</i> genes were evaluated using real-time polymerase chain reaction. The results indicated that meat from corn-silage supplementation exhibited higher levels of oxidation than those from pasture-fed steers. Also, results showed that meat from corn-silage-supplemented steers were more oxidised than those from pasture-fed steers. Moreover, hydrophilic extracts showed higher levels of antioxidant capacity than liphophilic ones in boths feeding systems and the muscles of animals that received corn exhibited a 17% reduction in TPC. In addition, expression levels of <i>cat, sod</i> (1 and 2), and <i>gpx</i> genes were lower in this group compared to the pasture-finished group. Consequently, the gene expression of the antioxidant enzymes exhibited a negative correlation with lipid oxidation, and with lipophilic antioxidants. Conversely, a positive correlation was observed with polyphenol content. This study demonstrated that the oxidative stability of meat can be enhanced by feeding steers with pasture, rather than finishing with corn silage supplementation. Moreover, attributable to reduced expression levels of antioxidant enzymes, leading to higher lipid and protein oxidation levels, which has a deleterious effect on meat quality. Consequently, the gene expression of the antioxidant enzymes evaluated, specifically <i>sod, cat and gpx</i>, has been identified as a promising reliable biomarker for oxidative stability in meat.