Feeding Marine Polysaccharides to Alleviate the Negative Effects Associated with Weaning in Pigs

SIMPLE SUMMARY: Weaning is the most crucial event in commercial pig farms. It involves complex dietary, social, and environmental stresses that interrupt gut development in the pig. These stresses have been controlled with in-feed prophylactic antibiotics and dietary minerals. These strategies are under scrutiny because of their role with antimicrobial resistance and environmental contamination. There is an urgency to find alternative dietary supplements that can support growth and prevent diarrhoea in the weaned pig. Marine macroalgae and organisms offer an interesting source of novel bio-actives. The supplementation of intact (whole) seaweed has not been successful in the immediate post-weaned pig diet, probably due to negative interaction between the constituents on digestive health and performance. Supplementation with the purest forms of laminarin and fucoidan extracted from macroalgae and chitin derivatives appear to have the most benefit in terms of improvements in gastrointestinal health. This is due to their prebiotic, antibacterial, anti-oxidant, and immunomodulatory properties. The extraction methodologies and conditions used to extract these polysaccharides are also an important contributing factor to the biological properties of these polysaccharides. This review focuses on the feeding of laminarin, fucoidan, and chitin derivatives as suitable substitutes for in-feed prophylactic antibiotics and minerals. ABSTRACT: In young pigs, the challenge of weaning frequently leads to dysbiosis. This predisposes pigs to intestinal infection such as post-weaning diarrhoea (PWD). Dietary interventions to reduce PWD have centred on dietary inclusion of antibiotic growth promoters (AGP) and antimicrobials in pig diets, or high concentrations of zinc oxide. These interventions are under scrutiny because of their role in promoting multidrug resistant bacteria and the accumulation of minerals in the environment. There are significant efforts being made to identify natural alternatives. Marine polysaccharides, such as laminarin and fucoidan from macroalgae and chitosan and chito-oligosaccharides from chitin, are an interesting group of marine dietary supplements, due to their prebiotic, antibacterial, anti-oxidant, and immunomodulatory activities. However, natural variability exists in the quantity, structure, and bioactivity of these polysaccharides between different macroalgae species and harvest seasons, while the wide range of available extraction methodologies and conditions results in further variation. This review will discuss the development of the gastrointestinal tract in the pig during the post-weaning period and how feeding marine polysaccharides in both the maternal and the post-weaned pig diet, can be used to alleviate the negative effects associated with weaning.