Browsing by Subject "Intestinale Mikrobiota"

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Impact of dietary phosphorus and fermentable substrates on the immune system and the intestinal microbiota of the pig
(2016) Heyer, Charlotte Maria Elisabeth; Stefanski, Volker
Phosphorus (P) represents a crucial input for agriculture and food industries as a mineral present in ingredients used for livestock feeding as well as in mineral fertilisers. In the current systems, P is primarily derived from the finite mined phosphate rock resource. Thus, a critical challenge of global P scarcity is directly linked to future food security and sustainable resource management, especially in the European Union which is dependent on raw P from outside Europe. Apart from other future activities in animal nutrition, new dietary formulations of livestock diets emerged as a potential approach to increase the digestibility of plant P, phytate (myo inositol 1,2,3,4,5,6 hexakisphosphate, InsP6), and to reduce the supplementation with mineral phosphate. In non-ruminant animals, such as the pig, InsP6 hydrolysis is incomplete, as the small intestine lacks sufficient enzymes such as endogenous mucosal phytase and phosphatase. As a consequence, there is rising scientific interest to improve the understanding of InsP6 degradation in the digestive tract as well as the effects on nutritional factors and finally animal performance and health. The aim of the present thesis was to investigate the impact of dietary P, InsP6 and InsP6 hydrolysis products in combination with different fermentable substances (protein, carbohydrate) on the porcine immune system, the intestinal microbiota and animal health. First, a comprehensive literature overview describes the impact of P on the immune system and the microbiota along the gastrointestinal tract (GIT), including potential effects on host health with special focus on the pig. Secondly, an in vivo study with growing pigs was conducted to examine the effects of diets with varying mineral calcium-phosphorus (CaP) levels as well as different fermentable substrates on intestinal CaP concentration, InsP6 hydrolysis, the intestinal microbial ecosystem, and the peripheral and gut-associated immune system. In 2 consecutive experiments, 31 growing pigs (55 ± 4 kg) were allotted to a 2 × 2 factorial arrangement with 4 treatment groups, fed either a corn-soybean meal or a corn-pea based diet, each with 2 different CaP levels (low, 66% of the CaP requirement; high, 120% of the CaP requirement) supplemented with monocalcium phosphate and calcium carbonate. After 3 weeks of adaptation to the diets, all pigs were immunized twice with keyhole limpet hemocyanin (KLH). Blood and faeces samples were taken. After slaughtering, immunological tissue (jejunal, ileal mesenteric lymph nodes, spleen) as well as jejunal, ileal, caecal and colonic digesta were taken. Faecal and digesta samples were examined for P, Ca, inositol phosphate (InsP) isomers and for the marker titanium dioxide. The number of different leukocyte subpopulations analysed by flow cytometry, mitogen-induced lymphocytes proliferation in vitro were assessed. In addition, concentrations of plasma anti KLH IgM and plasma anti-KLH IgG analysed by ELISA and haematological parameters analysed by an automated hematology system have been measured in blood and tissue samples. In digesta samples, bacterial 16S rRNA gene copy numbers were determined by quantitative real-time PCR. The concentration of short chain fatty acids (SCFA) and ammonia was assessed. In addition, the use of terminal restriction fragment length polymorphism has been proven to characterize the structure of porcine gut microbiota. Results of the current study demonstrated that CaP and fermentable substrates had a distinct effect on the peripheral and gut-associated immune system, as well as on microbial composition and activity in growing pigs. High dietary CaP concentrations and the corn-pea diets increased P net absorption. Almost no InsP6 degradation could be observed in the GIT, and mainly myo inositol pentakisphosphate (InsP5) isomers were measured in jejunal, caecal digesta and faecal samples. In particular, the high CaP diets showed higher InsP6 and InsP5 concentrations, indicating a reduction of the initial steps of P release from InsP6 and a further breakdown of InsP5 isomers. The low CaP content might cause an impaired first line of defence and activation of the cellular and humoral adaptive immune response. As an example, the high CaP content affected the outcome of the adaptive immune response including a higher number of antigen experienced T-helper cells in the blood as well as higher plasma anti-KLH IgG concentrations. The reactivity of blood and mesenteric lymph node lymphocytes to Concanavalin A in these pigs was impaired, indicating modulating effects of other origin such as migration patterns or activity of antigen-presenting cells. Since results of the present study suggest contradictory effects of CaP level on immune cell numbers and lymphocyte reactivity in vitro and in vivo, further studies are needed to determine effects on cell signalling such as cytokine production profiles. Moreover, the high CaP content and the soybean meal diets increased the number of butyrate-producing bacteria, such as Eubacterium rectale and Roseburia spp. and increased the concentration of various SCFA in the small and large intestine, thereby contributing to improve gut health. Potentially harmful bacteria, such as Enterobacteriaceae and Bacteroides Prevotella Porphyromonas, were increased by the low CaP level and pea diets, indicating a less healthy microbiota. Results demonstrated that both, CaP supply and the amount of fermentable substrates, may beneficially affect gut health due to modulations of the composition and activity of the intestinal microbiota. Further studies should evaluate the impact of CaP on specific pathogenic bacteria known to produce toxic products creating a direct link to the immune system and animal health. Although most parameters of the present study indicate a positive effect of the high CaP diet, not all values showed a consistent effect on animal health, such as immune cell numbers and lymphocyte proliferation in vitro. In conclusion, variations in P availability and the formation of individual InsPs have to be considered when formulating diets in support of a stable intestinal microbial ecosystem and immune functions of the host.