Early-Life Oat Supplementation Is Associated with Altered Cecal Microbiota and Microbial Metabolic Profiles and Reduced Campylobacter jejuni Colonization in Broiler Chickens

Campylobacter jejuni is a leading foodborne pathogen that commonly colonizes the intestinal tract of broiler chickens and represents a significant food safety concern. Dietary intervention may provide a practical approach to modulate the gut microbiota and reduce pathogen colonization. This study investigated the effects of oat supplementation on C. jejuni colonization and dissemination, cecal microbiota and predicted functions, and cecal short-chain fatty acids (SCFAs) and ileal amino acid profiles during early-life infection in broiler chickens. One-day-old Ross 308 broiler chickens were fed a basal diet or diets containing 10% oat (MDF) or 20% oat (HDF) and orally infected with C. jejuni at 2 days of age. C. jejuni loads in the cecum, jejunum, liver, and spleen were quantified by culture. Cecal microbiota composition and predicted functional profiles were characterized by shotgun metagenomic sequencing, while cecal SCFAs and ileal amino acids were quantified at 21 and 35 dpi using gas chromatography and an automatic amino acid analyzer, respectively. Oat supplementation reduced intestinal C. jejuni loads and limited dissemination to the liver and spleen, with the MDF diet reducing cecal loads by up to 3.3 log10 CFU/g at 35 dpi (p < 0.05). Infection altered cecal microbial diversity and community structure, while oat supplementation modified these infection-associated microbial patterns, with MDF showing the most consistent effects. Differential abundance analysis identified changes in taxa, including Bacteroides, Parabacteroides, and Phocaeicola, together with changes in predicted functions related to motility and chemotaxis, iron acquisition, and dormancy/sporulation. These microbial changes coincided with alterations in cecal isobutyrate and ileal amino acids, particularly glutamate, serine, proline, and aspartate, in MDF-fed infected chickens. Overall, MDF supplementation was most consistently associated with reduced C. jejuni colonization and dissemination and concurrent changes in the developing cecal microbial and metabolic profiles.