A wheat-based diet enhances colonization with the intestinal spirochaete Brachyspira intermedia in experimentally infected laying hens

This study investigated the influence of feeding diets based on cereals with different non-starch polysaccharide content on colonization with the intestinal spirochaete Brachyspira intermedia in experimentally infected laying hens. The diets were based on wheat, barley, or barley and sorghum, all with or without supplementation with exogenous dietary enzymes. Six groups of 12 individually caged laying hens were fed the respective diets for 2 weeks, and then challenged at 20 weeks of age by crop tube with 10(8) to 10(9) colony forming units of active motile spirochaetes on five successive days. Eggs were collected daily. The birds were weighed weekly, and caecal faeces collected for assessment of water content. Every 3 to 4 days cloacal swabs were collected and subjected to culture and subsequent polymerase chain reaction for B. intermedia. The birds were killed at 27 weeks of age. Caecal contents were cultured for spirochaetes, and the viscosity of the ileal and rectal contents assessed. Dietary soluble non-starch polysaccharide content was not a consistent predictor of viscosity in the ileum, and the addition of enzymes did not significantly reduce the viscosity. A dietary influence on colonization was observed, with birds fed wheat having significantly more colonization than the birds fed the other diets. No significant association was found between either dietary soluble non-starch polysaccharide content or ileal viscosity and colonization with B. intermedia , as assessed by faecal excretion of the spirochaete. Dietary enzymes did not consistently or significantly reduce colonization. It was not established how wheat enhances colonization by B. intermedia , but the results suggest that wheat-based diets should be avoided in flocks infected with B. intermedia.