Protection and stimulation of intestinal innate immunity using mannan oligosaccharides

Abstract

Necrotic enteritis (NE) caused by Clostridium perfringens is a re-emerging disease of economic importance in areas of the world where antibiotic growth promoters have been banned. Various alternatives to antibiotic growth promoters are being tested including prebiotics known as mannan oligosaccharides (MOS) which have been shown to mitigate the effects of NE and potentially boost the immune system, though the mechanism is not completely understood. The objective of this study is to test the effectiveness of MOS on balance of microbial populations, gut morphology and immune system ability; specifically: C. perfringens genetic populations, villi architecture and TLR2 and TLR4 activity. This study focuses on organic broiler chickens fed MOS at 0, 2, 4, 6 and 8g/kg feed and challenged with an inoculation of C. perfringens isolated from an outbreak on a local organic farm. Toxinotype and 16S phylogenetic analysis of C. perfringens were reviewed as well as feed efficiency, gut morphology and gene expression of Toll Like Receptors 2 and TLR4 using qRT-PCR. All field isolates were found to be Type A C. perfringens, as were most experimental isolates except for two isolates taken pre-innoculation, which were more likely attributed to contamination of the experiment room by cattle which were housed there previously. No association between pathogenecity and toxin genes cpb2 or netB could be established during this study. 16S analysis found all C. perfringens isolates to be highly related, though there seemed to be a change in populations post inoculation which did match the field isolate used for inoculation. Gut morphology readings including villi height, width and area, crypt depth and lymphocyte and goblet cell concentrations showed some significant effect though it was not in a common area of the intestine and was often due to the interaction between treatments and time. These results also failed to reproduce effects found by other authors. TLR2 and 4 were not found to be significantly different between treatments, though certain trends were noted. The lack of significant treatment effects as well as the low reproducibility of these outcomes leads to the conclusion that, though MOS may contribute to gut health and maturity based on these and conclusions found by other authors, its effect is hinging on other factors such as management and nutrition.