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

Abstract

Meat is highly susceptible to oxidation, which leads to the degradationof lipids and proteins, resulting in undesirable changes in meatquality, such as colour and shelf life. This process can be mitigatedby both non-enzymatic antioxidants and enzymatic antioxidants,including superoxide dismutase (SOD), catalase (CAT), and glutathioneperoxidase (GPx). The oxidative stability of meat is influencedby several factors, including animal nutrition. The aim of thisstudy was to assess the impact of corn silage supplementation onmeat oxidative status and its correlation with the expression level ofgenes associated with this process in the longissimus thoracis etlumborum muscle of Braford steers. For this study, 30 steers wererandomly assigned to two experimental groups of 15 animals each.One group was fed with ad libitum pasture supplemented with cornsilage and the other group was fed with ad libitum pasture. Thedegree of protein and lipid oxidation was determined by totalprotein carbonyl content and lipid degradation products, respectively.The antioxidant capacity was determined by measuring theradical-scavenging activities, total phenol content (TPC), and theactivities of the CAT, SOD, and GPx enzymes. In addition, therelative levels of sod (1 and 2), cat, and gpx genes were evaluatedusing real-time polymerase chain reaction. The results indicatedthat meat from corn-silage supplementation exhibited higher levelsof oxidation than those from pasture-fed steers. Also, resultsshowed that meat from corn-silage-supplemented steers weremore oxidised than those from pasture-fed steers. Moreover, hydrophilicextracts showed higher levels of antioxidant capacity thanliphophilic ones in boths feeding systems and the muscles ofanimals that received corn exhibited a 17% reduction in TPC. Inaddition, expression levels of cat, sod (1 and 2), and gpx genes werelower in this group compared to the pasture-finished group.Consequently, the gene expression of the antioxidant enzymesexhibited a negative correlation with lipid oxidation, and withlipophilic antioxidants. Conversely, a positive correlation wasobserved with polyphenol content. This study demonstrated that the oxidative stability of meat can be enhanced by feeding steerswith pasture, rather than finishing with corn silage supplementation.Moreover, attributable to reduced expression levels of antioxidantenzymes, leading to higher lipid and protein oxidation levels,which has a deleterious effect on meat quality. Consequently, thegene expression of the antioxidant enzymes evaluated, specificallysod, cat and gpx, has been identified as a promising reliable biomarkerfor oxidative stability in meat.