Modification of lipid composition and oxidation in porcine muscle and muscle microsomes as affected by dietary supplementation of n-3 with either n-9 or n-6 fatty acids and α-tocopheryl acetate

The effect of different oil combinations: olive oil (20g/kg), sunflower oil (20g/kg), linseed oil (5g/kg) and either olive (15g/kg) or sunflower oil (15g/kg) and α-tocopheryl acetate supplementation (200mg/kg feed) on fatty acid composition and lipid oxidation of pig muscle and muscle microsomes was investigated. The proportions of α-linolenic acid (P<0.001), eicosapentaenoic acid (P<0.001) and docosahexaenoic acid (P<0.05) in neutral lipids were significantly greater when linseed oil was added to diets. However, the proportion of docosahexaenoic acid in polar lipids was not significantly affected by the addition of linseed oil to the diets. Adding n-3 fatty acids in the diet produced a higher (P<0.05) linoleic acid proportion in muscle neutral lipids, particularly in those groups fed n-9 MUFA. Pigs fed n-9 and n-3 enriched diets had the closest n-6:n-3 ratio to human dietary recommendations. The addition of linseed oil produced a significantly (P<0.05) lower proportion of oleic acid (C18:1n-9) in polar lipids of muscles from pigs fed olive and linseed oils (OL + LIN), but not in those fed sunflower and linseed when compared with groups fed diets not enriched with linseed oil. Supplementation with 200mg α-tocopheryl acetate/kg feed also led to higher (P<0.05) oleic acid concentrations in polar lipids. Muscle from the pigs fed sunflower and linseed oils had significantly (P<0.05) higher Thiobarbituric acid Reactive Substances (TBARS) values throughout the study compared to those fed olive and linseed oils. α-Tocopheryl acetate supplementation consistently improved lipid stability. No interactions between α-tocopherol and oils were observed on lipid oxidation. Iron-induced peroxidation showed a similar trend to that observed for TBARS development. Iron-induced peroxidation of muscle microsomes showed a similar trend to oxidation in muscle. No interactions were detected between different oils in muscle microsomes. The partial replacement of n-9 MUFA (as olive oil) by n-3 PUFA in diet, results in a small increase in muscle and membrane lipid oxidation and could be an interesting alternative in pig diet formulation.