Dietary Phytonutrients Enhance Gut Innate Immunity, Modulate Gut Microbiota and Improve Disease Resistance to Coccidiosis and Necrotic Enteritis in Broiler Chickens

The human population is projected to grow to 9-10 billion by the year 2050. As a consequence of the population explosion, food animal production must confront a new array of challenges. Among these are global food security, climate change, emerging infectious diseases, regulatory ban of antimicrobials, high-density production conditions, and waste management. In order to assure continuity in the supply of poultry food products, effective control measures against infectious diseases in the framework of environmental change are critical. In the United States, Clostridium-related diseases, such as gangrenous dermatitis (GD) and necrotic enteritis (NE), and coccidiosis are among the most important infectious diseases in chickens and turkeys. These infectious diseases are associated with intestinal inflammation and when undetected, they can decrease the efficiency of nutrient utilization of growing birds. Antimicrobials blended with antibiotics and anticoccidial drugs in food animal production are commonly practiced. In-feed antimicrobials are well known to affect gut microbiota due to their apparent in vitro antimicrobial properties. In addition, the evidence is increasing that gut microbiota plays an important role in health, immunity and disease prevention. The published data in mice and humans support that altered microbiota is linked to obesity, inflammatory bowel disease (IBD) or atherosclerosis. Overall, there is a cross talk among immunity and gut microbiota and we need to fully understand this to develop strategies for sustainable agricultural production of food animals. Dietary antimicrobials influence gut microbial community and the development and regulation of the host immune systems. Therefore, any non-drug alternative disease intervention strategies (e.g., nutrients, environment, antimicrobials, and feed additives, etc.,) that may alter gut microbiota could affect the protective immune responses to enteric pathogens including Eimeria spp., Salmonella spp. and Clostridium spp. Based on the published literatures, it is clear that disturbance of gut microbial community by dietary antimicrobials, singly or in combination with antibiotics and antibiotic ionophores could negatively influence gut homeostasis and immune system. Especially, there is increasing evidence that low-level inclusion of antimicrobials, e.g., antibiotics, antibiotic-like coccidiostats and chemicals may render the host susceptible to the enteric disease such as Clostridium spp. This presentation will highlight our recent in vivo studies showing the effects of antimicrobials on gut microbiota and host immune systems of chickens, and the mode of immunomodulation by plant-derived phytonutrients. The interaction of gut microbiota and host immunity is closely linked to the outcome of host-pathogen interaction and further studies to investigate the role of dietary antimicrobials on the complex interaction of host-pathogen-microbiota-antimicrobials in poultry will be necessary.