Fatty acids, tocopherols and lipid oxidation in pig muscle

The objective of this thesis was to investigate the effect of rearing conditions, sex, and RN genotype on the fatty acid composition in polar and neutral lipids, content of antioxidants, and lipid oxidation in pig muscle. Furthermore, the effect of different dietary levels of various polyunsaturated fatty acids (PUFA) on rat performance was investigated. Pigs were reared in outdoor or indoor rearing systems and fed different diets of conventional and organic origin. All pigs were slaughtered at approximately 105 kg live weight and samples were collected from M. longissimus dorsi and M. Biceps femoris for lipid analysis. Outdoor rearing increased the level of PUFA n-3 in the neutral lipids of pig muscle. The increase was rather small and the effect on oxidative stability can be considered as minor, especially as outdoor pigs had a higher content of tocopherols. In addition, our studies showed a more pronounced increase of PUFA level in females and entire males, due to diet and outdoor rearing, compared with castrated males. This difference in PUFA level is suggested to depend on grazing behaviour, incorporation of PUFA into fat tissues or a slight alteration of PUFA metabolism, possibly mediated by light. The level of PUFA in neutral lipids was higher in entire males compared with females and castrated males, which can partly be explained by lower body fat accumulation. In polar lipids the level of highly unsaturated fatty acids was higher in entire male and female pigs compared with castrated males, which indicates that the desaturation and elongation of PUFA are more pronounced in sexes with an intact reproductive function. The RN genotype was found to influence the fatty acid composition in the polar lipids of pig muscle suggesting involvement of PUFA in glycogen metabolism or that the RN genotype itself affects PUFA metabolism. Finally, feeding rats for approximately 39 days with linseed oil or sunflower oil diet improved wound healing. There was a positive correlation between PUFA n-3 fatty acids in liver and wound healing. Thus, the higher levels of PUFA in tissues covariating with the diet and the demonstrated increased wound healing, revealed a potential of PUFA in affecting the performance of animals.