Microbial Activity in the Large Intestine of Chicks Fed Diets with Different Types and Levels of Inulin

The aim of the study was to evaluate the effects of dietary level of two types of inulin differing in the degree of polymerization (DP) on microbial activity in the large intestine of chicks. The experiment was performed on 70 one-day-old Ross 308 male chicks divided into 7 groups fed starter-type diets without inulin addition or supplemented with 0.2%, 0.4% or 0.6% of inulin with DP≥10 (IN10), or DP≥23 (IN₂₃). After 14 days of feeding birds were sacrificed to collect digesta samples from caeca and colon. Caecal digesta was examined for pH, concentrations of short-chain fatty acids (SCFA) and amines, activities of β-glucosidase and mucinase, and relative amount of selected bacterial populations, whereas in colonic digesta only pH, SCFA and amines were analysed. Regardless of DP, inulin level did not affect digesta pH, activity of bacterial enzymes and relative amounts of Clostridium spp., Lactobacillus spp., Bifidobacterium spp. and E. coli populations. Dietary level of IN₁₀ significantly affected propionic acid concentration, which was greater in caecal digesta of birds fed diet supplemented with 0.2% of IN₁₀ compared to other groups and feeding diets supplemented with all levels of IN₁₀ significantly reduced histamine concentration compared to the control. There were no effects of inulin on microbial activity indices in the colon. The present study indicates that, regardless of DP, inulin does not modify considerably microbial activity in the large intestine of chicks.