Design and evaluation of a probiotic supplement to enhance gut health in broiler chickens

Thesis Abstract

The widespread reliance on antibiotics in poultry production to enhance growth performance and prevent diseases has raised significant concerns regarding antimicrobial resistance and food safety, thereby necessitating alternative strategies to promote gut health in broiler chickens. This study aims to design, formulate, and evaluate a probiotic supplement specifically targeted at improving intestinal health, nutrient absorption, and overall growth performance in broiler chickens. The specific objectives include identifying effective probiotic strains, determining optimal dosages, assessing the impact of the supplement on gut microbiota composition, and evaluating the subsequent effects on growth metrics and immune response. Employing a randomized controlled experimental design, the study recruited a total of 150 one-day-old Cobb broiler chicks, randomly allocated into five groups of 30 each a control group receiving a basal diet without probiotics, three treatment groups receiving basal diets supplemented with varying doses (1×10^8, 1×10^9, 1×10^10 CFU/kg feed) of a multi-strain probiotic formulation, and a positive control group receiving a standard antibiotic growth promoter. The probiotic formulation comprised well-characterized strains of Lactobacillus acidophilus, Bifidobacterium bifidum, and Enterococcus faecium. Data collection involved weekly measurements of body weight and feed intake, mortality rates, and post-mortem gut histopathology at day 42. Fecal samples collected at multiple time points were analyzed via 16S rRNA gene sequencing to characterize gut microbiota dynamics, and Lactobacillus and Bifidobacterium enumeration was performed using selective culture techniques. Blood samples were analyzed for immune markers, including immunoglobulin A (IgA) and cytokine levels, using enzyme-linked immunosorbent assay (ELISA). Validity and reliability of the microbiological and immunological assays were established through calibration with standards and repeat testing, respectively. Data analysis employed analysis of variance (ANOVA) to examine differences in growth performance, microbiota diversity indices, and immune parameters among groups, followed by Tukey’s post hoc tests for pairwise comparisons. Regression analyses explored dose-response relationships, while principal coordinate analysis (PCoA) was used to visualize microbiota compositional changes. Theoretical frameworks grounded in the Ecological Theory of Gut Microbiota and the Hygiene Hypothesis underpin the interpretation of results, complemented by a conceptual model illustrating probiotic influence on gut health parameters. Expected findings include significant improvements in growth rates, feed conversion ratios, and immune status in probiotic-treated groups compared to controls, with optimal effects observed at the 1×10^9 CFU/kg dosage. Microbiota analysis is anticipated to reveal increased diversity and relative abundance of beneficial microbes, alongside reduced pathogenic bacterial populations. These findings will contribute novel insights into the specific probiotic strains and doses that effectively enhance gut health, modulate immune responses, and improve production metrics in broiler chickens, thereby addressing the urgent need for antibiotic alternatives in poultry farming. The study’s primary contributions to knowledge involve establishing evidence-based probiotic formulations optimized for poultry, elucidating mechanisms through microbiome and immunological analyses, and providing a scalable, cost-effective intervention model. Critically, the findings are expected to inform best practices and policy recommendations regarding probiotic use, supporting sustainable and safe poultry production systems. The research concludes with recommendations for integrating tailored probiotic strategies in commercial broiler operations, and suggests avenues for further long-term studies examining probiotic stability, strain-specific effects, and broader implications on poultry gut microbiota ecology.