The Gordon Memorial Lecture: Steering the gut microbiome for improved health and welfare in broilers.

1. In fast growing broilers, intestinal health is continuously under pressure due to extremely high feed intake and environmental/management conditions that cause (oxidative) stress to the intestinal epithelium.2. The following review focuses on the contributions of the Livestock Gut Health Team at Ghent University into understanding the mechanisms governing the interactions between the intestinal microbiota and the host intestinal mucosa. It covers the development of tools to support intestinal health of broilers through nutritional manipulation of the microbiota.3. In the duodenum and jejunum, microbiota are suppressed by the secretion of enzymes and antibacterial peptides in order to avoid competition for the nutrients. These defence mechanisms can be re-enforced and/or the epithelial cells can be protected from damage by different feed additives.4. Metabolism in the caecal microbial network is fuelled by the fibre fraction in feed. Whenever this network is incomplete or the feed is lacking fibre, this may lead to a distortion of the microbiota, followed by insufficient production of beneficial microbial metabolites, such as butyrate. This can contribute to inflammation and leakage of the gut barrier, with, in severe cases, wet litter, foot pad lesions and poor performance as common consequences. Reenforcing the caecal microbial network can be achieved using prebiotics, probiotics and postbiotics, which will improve the health and well-being of the birds.5. Steering towards optimal microbial fermentation will help to protect the birds from Clostridium perfringens-associated necrotic enteritis and Salmonella spp. colonisation since both interact with the intestinal microbiota.