Effect of Flaxseed and Alpha Tocopherol Supplementation of Pig Diets on Fatty Acid Content and Lipid Oxidation Stability of m. Longissimus

Trakia University, Faculty of Agriculture, BG - 6000 Stara Zagora, Bulgaria


DOYCHEV, V. and G. MIHAYLOVA, 2013. Effect of flaxseed and alpha tocopherol supplementation of pig diets on fatty acid content and lipid oxidation stability of m. Longissimus. Bulg. J. Agric. Sci., 19: 1416-1424


The experiment was carried out with 70 fattening hybrid pigs (45-110 kg) divided into 5 groups of 14 (7 castrated males and 7 females). Pigs were fed compound feed containing 13.24% CP and 12.04 MJ ME/кg. During the last two months of the fattening period (78–120 kg) the compound feed of pigs from groups ІІ, ІІІ, ІV and V (experimental) was supplemented with flaxseed at different levels: group II – 4%, group III – 8%; groups IV and V – 12%. The feed of pigs from group V was also supplemented with vitamin E (alpha tocopherol acetate) at 200 mg/kg. Pigs were slaughtered at 120 kg live body weight. The fatty acid contents of triacylglycerols and phospholipids were determined in m. Longissimus samples. Oxidative changes in m. Longissimus meat were assessed in fresh samples and in samples stored at –18°С for 6 months.
Linolenic acid content of triacylglycerols increased in experimental groups, being statistically significant higher in group II (Р<0.01), III, IV and V (Р<0.001) vs group I. Linoleic acid concentrations also differed between groups II and III (Р<0.05), group II and both groups IV and V (Р<0.001) and groups III and IV (Р<0.01). Compared to control pigs, eicosapentaenoic acid content in tissue triacylglycerols was higher in group III (Р<0.05), IV and V (Р<0.01). Significant differences were also established in groups IV and V vs group II (Р<0.05). Linoleic acid content decreased in group III vs group I (Р<0.05) and group II (Р<0.01), whereas arachidonic acid changed only slightly. The PUFA content was also insignificantly altered. Compared to the non-supplemented group, the PUFA/SFA ratio was substantially higher in groups II, IV and V (Р<0.01) and III (Р<0.05). The n-6/n-3 ratio in groups III, IV and V was significantly lower than that of groups I and II (Р<0.001). The difference between groups I and II was also considerable (Р<0.001).
Linolenic acid in tissue phospholipids of group III was significantly more than that in groups I (Р<0.01) and II (Р<0.05). In groups IV and V, the content f this fatty acid was higher than that in groups I, II (Р<0.001) and III (Р<0.01). The eicosapentaenoic acid in groups IV and V was considerably higher than that in control (Р<0.05). There were no statistically significant differences between groups with regard to fatty acid groups. The n-6/n-3 ratio was lower in group II vs group I (Р<0.05) and in groups III, IV and V (Р<0.001) vs group I. The differences between groups IV and V vs group II were also important (Р<0.01).
The high content of PUFA in tissue lipids resulted in significantly higher thiobarbituric acid number in both fresh and stored meat.

Key words: pigs, flaxseed, fatty acid composition, triacylglycerols, phospholipids, vitamin E, oxidation
Abbreviations:MDA – malondialdehyde; MUFA– monounsaturated fatty acids; SFA – saturated fatty acids; UFA – unsaturated fatty acids; ME – metabolizable energy; PUFA – polyunsaturated fatty acids; CP – crude protein; TBARS – thiobarbituric acid reactive substances; n-3 – omega-3; n-6 – omega-6.

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