Abstract
This study investigated the effect of dietary manipulations on muscle fatty acid composition, the activities and relative mRNA expressions of antioxidant enzymes and the relationship between muscle enzyme activity or mRNA expression and alpha linolenic acid (ALA) concentration in sheep. Eighty-four lambs blocked on liveweight were randomly allocated to four dietary treatments, lucerne pasture (Lucerne), annual ryegrass pasture (Ryegrass), feedlot pellets (Feedlot) or annual ryegrass plus feedlot pellets (RyeFeedlot). After six weeks of feeding, lambs were slaughtered and within 30 min post-mortem, samples collected from the longissimus lumborum (LL) muscle for RNA isolation and measurement of antioxidant enzyme activities. At 24 h post-mortem, LL samples were collected for determination of fatty acid concentrations. Feedlot treatment decreased ALA, eicosapentaenoic (EPA), docosapentaenoic (DPA) and docosahexaenoic (DHA) concentrations compared with other treatments and increased linoleic acid (LA) and arachidonic acid (AA) compared with Lucerne and Ryegrass (p < 0.001). The activity of Glutathione peroxidase (GPX1, p < 0.001) and Superoxide dismutase (SOD2, p < 0.001) enzymes in the muscle increased with Lucerne compared to other treatments. Lucerne increased muscle gpx1 mRNA expression by 1.74-fold (p = 0.01) and 1.68-fold (p = 0.05) compared with Feedlot and other diets, respectively. The GPX1 (r2 = 0.319, p = 0.002) and SOD2 (r2 = 0.244, p = 0.009) enzyme activities were positively related to ALA. There was a positive linear relationship between muscle gpx1 (r2 = 0.102, p = 0.017) or sod2 (r2 = 0.049, p = 0.09) mRNA expressions and ALA concentration. This study demonstrates that diet can affect concentrations of ALA and other fatty acids as well as change activities and gene expression of antioxidant enzymes in muscle. Increased antioxidant activity may, in turn, have beneficial effects on the performance, health and wellbeing of animals and humans.
Highlights
Dietary fat concentration and composition are two of the major factors influencing basal energy metabolism, body fat deposition and muscle fatty acid composition [1,2,3,4]
feedlot pellets (Feedlot) diet reduced alpha linolenic acid (ALA) concentration by 50% in muscle compared with the lucerne pasture (Lucerne) diet; whereas, Ryegrass and RyeFeedlot diets had 15% and 40% lower ALA concentration than Lucerne fed lambs, respectively
Antioxidant enzymes activity of glutathione peroxidase 1 (GPX1) and SOD2 in the muscle longissimus lumborum (LL) were significantly increased by the Lucerne diet compared with other dietary treatments
Summary
Dietary fat concentration and composition are two of the major factors influencing basal energy metabolism, body fat deposition and muscle fatty acid composition [1,2,3,4]. Animals and humans consuming greater amounts of green plant materials and feeds from marine origin deposit greater concentrations of n-3, mainly alpha linolenic acid (ALA), the precursor n-3 fatty acid and their derivatives [1,6,7,8]. These effects were due to diets being rich in n-3 and n-6 precursor fatty acids and due to competition between these fatty acids for absorption at the enterocyte and peripheral tissue level, as they share common enzymes for desaturation and elongation processes [3,9,10]. This has heightened the interest in health-enhancing food products, which has led to producers and retailers focusing on farm animal products such as meat and milk with increased concentrations of health-promoting nutrients such as essential fatty acids, minerals and antioxidants [15,16,17,18]
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