The gut morphology and microbial balance of Noiler chickens fed diets containing supplemental levels of Saccharomyces cerevisiae.
Sustainable poultry production in tropical environments requires nutritional strategies that enhance intestinal integrity and microbial stability without reliance on antibiotic growth promoters. This study evaluated the effects of graded dietary supplementation with Saccharomyces cerevisiae on gut morphology and microbial balance in Noiler chickens, a dual-purpose genotype widely utilised in Nigeria. A total of 300 day-old mixed-sex Noiler chicks were randomly allocated to five dietary treatments in a completely randomised design. Birds received a basal diet supplemented with 0, 0.5, 1.0, 1.5 or 2.0% S. cerevisiae over 16 weeks. At the end of the trial, intestinal segments (duodenum, jejunum and ileum) were collected for histomorphometric evaluation, while caecal digesta were analysed for microbial populations using culture-based techniques. Data were subjected to one-way ANOVA, and means were separated using Tukey’s test at P < 0.05. Dietary yeast supplementation produced dose-dependent improvements in several indices of intestinal integrity. Although villus height was not significantly affected (P > 0.05), numerical increases were observed at 1.0–2.0% inclusion, with the highest value recorded at 2.0%. Crypt depth increased significantly (P < 0.05) at 1.5 and 2.0% inclusion; however, this was accompanied by a concomitant improvement in villus height-to-crypt depth (VH: CD) ratio, indicating enhanced epithelial turnover without pathological hypertrophy. The VH: CD ratio was highest (P < 0.05) in birds fed 2.0% yeast, reflecting superior absorptive capacity. Enterocyte width and muscular layer thickness were also significantly increased (P < 0.05) at inclusion levels of 1.0–2.0%, suggesting improved cellular maturation and intestinal motility. Goblet cell count, intestinal wall thickness and mucosal surface area were not significantly influenced, although numerical improvements were observed at higher supplementation levels. Microbial analysis of caecal contents revealed improved microbial balance in yeast-supplemented groups, characterised by increased populations of beneficial Lactobacillus spp. and reduced counts of Escherichia coli relative to the control. Total aerobic bacterial counts remained within physiological ranges across treatments. These findings indicate that S. cerevisiae modulated gut microbial ecology towards a more favourable profile, potentially through competitive exclusion of pathogens and the immunomodulatory actions of yeast-derived β-glucans and mannan-oligosaccharides. Overall, supplementation with S. cerevisiae, particularly at 1.0–2.0% inclusion, enhanced intestinal architecture and microbial stability in Noiler chickens. The observed improvements in villus structure, epithelial dynamics and beneficial microbial populations suggest enhanced nutrient utilisation and gut health. These results support the strategic incorporation of probiotic yeast as a sustainable feed additive for improving gastrointestinal functionality and productivity in dual-purpose poultry systems under tropical production conditions.
Keywords: Noiler chicken, probiotic yeast, intestinal morphology, villus height, microbial ecology, sustainable poultry nutrition.
