Impact of Dietary Supplementation on Gut Microbiota in Free-range Poultry

Thesis Abstract

The health and productivity of free-range poultry are intricately linked to the composition and diversity of their gut microbiota, which in turn are influenced by dietary factors and environmental conditions. Despite the increasing popularity of free-range systems for poultry production, there remains limited empirical data on how specific dietary supplementation strategies modify gut microbial communities and, consequently, impact bird growth, immunity, and overall welfare. This study aims to evaluate the impact of targeted dietary supplementation with probiotics, prebiotics, and phytogenic feed additives on the gut microbiota profiles of free-range poultry, with a focus on identifying shifts in microbial diversity, abundance of beneficial microorganisms, and associated metabolic functions. The specific objectives include (1) quantifying changes in gut microbial diversity using 16S rRNA gene sequencing, (2) assessing the effects of supplementation on the relative abundance of probiotic bacteria such as Lactobacillus and Bifidobacterium, (3) examining shifts in pathogenic bacteria populations, and (4) correlating microbiota changes with poultry growth performance parameters and immune responses. The research employs a randomized controlled trial design involving 150 sixty-day-old indigenous free-range chickens, sourced from a commercial farm, and randomly assigned to five groups with 30 birds each. Four experimental groups receive different dietary supplements—probiotics, prebiotics, phytogenic additives, and a combination thereof—while one control group receives a basal diet. Data collection entails gut content sampling at 90 days of age, followed by genomic DNA extraction for high-throughput sequencing of the V3-V4 regions of the 16S rRNA gene using an Illumina MiSeq platform. Microbiome data will be analyzed through bioinformatics pipelines to determine alpha and beta diversity indices, taxonomic composition, and functional pathway predictions via PICRUSt. Growth performance measures (feed intake, weight gain), immune parameters (serum antibody titers, leukocyte profiles), and health indicators (mortality, lesion occurrence) are recorded throughout the study. Statistical analysis will include analysis of variance (ANOVA) for microbial diversity metrics and physiological data, coupled with regression models to identify associations between microbiota composition and performance traits. Principal coordinate analysis (PCoA) and differential abundance testing (DESeq2) will elucidate microbiota shifts attributable to dietary interventions. It is anticipated that supplementation, especially with probiotics and prebiotics, will significantly enhance gut microbial diversity, promote proliferation of beneficial microbes, reduce pathogen load, and improve immune function, thereby leading to better growth and health outcomes. These findings are expected to deepen understanding of host-microbe interactions in free-range poultry systems and contribute a microbiota-focused basis for optimizing dietary strategies in organic and sustainable poultry production. This research aims to fill existing gaps in knowledge regarding microbiome modulation through diet in free-range poultry, providing evidence-based recommendations for enhancing animal health and productivity via targeted microbial management. The study’s outcomes are expected to inform feed formulation practices and support the development of nutritional interventions that promote resilient gut ecosystems in free-range and organic poultry farms. The contribution to scientific knowledge extends to elucidating the specific microbial signatures associated with improved performance and health in free-ranging birds, thereby advancing the field of animal microbiome research and sustainable livestock management. Conclusively, the study advocates for integrated dietary strategies tailored to microbial enhancement, with policy implications for organic poultry certification standards and farm management practices aimed at fostering holistic animal well-being.