Lipids and fatty acids play major roles in relation to mucosal immune responses, epithelial barrier functions, oxidative stress and inflammatory reactions. The composition of fatty acids and their molecular structures (chain length and number of double bonds) influences digestion, absorption and metabolism of the dietary fat, as well as the bioactivity of the fatty acids. Piglets post weaning having immature intestines and immune functions are very vulnerable towards invading microorganisms. Manipulation of the milk fatty acid composition via the sow nutrition, or inclusion of dietary fat sources in the feed, may be used as a strategic tool to enhance pig performance and their gut health pre- and post weaning. Medium-chained fatty acids (MCFA) are absorbed directly into the portal blood and may contribute with immediate energy for the piglet. In addition, the MCFA possess antibacterial effects. The essential fatty acids, linoleic and linolenic fatty acids, form the building blocks for the longer –chained polyunsaturated n-3 and n-6 fatty acids. Their conversion into n-3 and n-6 eicosanoids influence the inflammatory reactions and the immune responses upon bacterial challenge. The proportion of unsaturated fatty acids in the cell membranes influence the susceptibility to oxidative stress. Oxidative stress accompanies infectious diseases, and if uncontrolled, the development of the lipid peroxides may be harmful for the epithelial barrier function. The aim of this presentation is to review how dietary fatty acid composition during critical phases of pigs’ lives can support a normal immune system and modulate resistance to infectious diseases of pigs, and influence growth of the pig. Furthermore, factors that can enhance oxidative stress (e.g. polyunsaturated fatty acids), uncontrolled inflammatory reactions (e.g. high ratio of n-6 to n-3 fatty acids in cellular membranes), and limit immune development (such as deficiency of fat-soluble vitamins), and be harmful for the pig gut health are addressed.
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