Effect of phytate degradation using phytase and soaking and resistant starch in barley on phosphorus utilization, gut health, and growth in pigs

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The primary storage form of P in plant seeds is phytate (any salt of myo-inositol 1,2,3,4,5,6-hexakis (dihydrogen phosphate); InsP6) that is poorly available for non-ruminant animals, such as the pig. Depending on activity of phytases and other phosphatases, InsP6 is hydrolyzed down to less phosphorylated inositol phosphates, such as myo-inositol, and available P. Feed processing techniques such as soaking and fermentation that promote activation of phytases to reduce InsP6 concentration in feed have gained in importance. Furthermore, InsP6 is an anti-nutritional factor in pig feed by chelating positively charged cations and affecting utilization of other dietary nutrients. Results on the interaction between P and the immune system are inconsistent, several studies in different species have shown a positive impact of dietary P and phytase supplementation on the adaptive immune response. Recent studies indicate that individual inositol phosphates or phosphate may also affect properties of the intestinal microbiota, including pathogenic microorganisms. The proposed study assesses effects of inositol phosphate degradation (using soaking, fermentation and microbial phytase supplementation) and resistant starch (low vs. high fermentable barley cultivars containing high and low amylose, respectively) in situ and in vivo using pigs on P utilisation, gut health and growth. The milestones of the proposed research project are: (1) Evaluation of the enzymatic degradation of phytate in situ using soaking and fermentation; (2) Effects of diets containing phytase supplementation and low vs. high fermentable barley cultivars soaked with lactic acid bacteria on nutrient digestibility, and (3) Impact of diets containing phytase supplementation and low vs. high fermentable barley cultivars soaked with lactic acid bacteria on growth performance in nursery pigs with special focus on the gastro-intestinal microbiota and immune system. The advantages of the planned research work are: (1) Results of the metabolism of InsP6 and lower inositol phosphates in vivo can be used target further increase InsP6 digestibility, to reduce supplementation with phosphate and to minimize P pollution from manure; (2) Using processing strategies (soaking and fermentation) and the supplementation of microbial phytase to the diet improves the understanding of phytase activity of different origins, and evaluates potential synergistic effects; (3) Description of the complex relationship between InsP6 in combination with starch using a common cereal, the gastro-intestinal microbiota and the immune system can be used to beneficially affect swine health and performance.