Feed for defence : can dietary supplements modulate broiler gut microbiota and guard against Campylobacter?

Sammanfattning: The bacteria Campylobacter jejuni is the causative agent of a disease in humans called campylobacteriosis and is the most commonly reported zoonosis in the European Union, with the primary source of infection often traced to broiler products. While low overall C. jejuni prevalence is reported in conventional broiler production in northern Europe, heightened incidences persist in summer months, particularly in organic production. Supplementing broiler diets with dietary components rich in lactic acid bacteria or complex polysaccharides have been identified as promising measures to decrease Campylobacter presence in various production systems. This thesis investigated the effect of daily consumption of Lactiplantibacillus plantarum 256 (LP256)-supplemented water, silage inoculated with LP256 and haylage (a non-inoculated forage similar to silage) on C. jejuni colonisation and microbiota composition. The effects of supplementing broiler feed with algal extract on development of caecal microbiota and colonisation by C. jejuni were also examined. Daily intake of LP256 and algal extract diet supplementation proved ineffective as interventions against C. jejuni colonisation. The treatments did not alter broiler microbiota composition, although shifts occurred after C. jejuni challenge, suggesting that colonisation affected the gut microbiota. Adding LP256 to water improved broiler initial weight. Inclusion of forages in the diet of slower-growing hybrids did not compromise performance, but in fast-growing hybrids, the incorporation of haylage showed adverse effects. These findings improve understanding of microbial interactions in the gut of broiler chickens, but the observed changes need to be validated in future research.