Sessions

The gut microbiota of poultry plays a pivotal role in nutrient utilization, immune homeostasis, and protection against pathogens; therefore, dysbiosis associated with Salmonella enterica and Escherichia coli infections represents a major animal health and public health concern. In the context of the spread of antimicrobial resistance and the need to reduce antibiotic use, the importance of phytogenic feed additives that can beneficially modulate the microbial community even under infectious pressure is increasingly recognized. The aim of this study was to evaluate how different doses of a phytogenic additive containing fenugreek and turmeric extracts influence the diversity and community structure of the gut microbiota in Bábolna Tetra-SL chickens in a dual-infection model.

The experiments were conducted on 270 one-day-old chicks. The study groups included a non-infected negative control, an infected positive control, an enrofloxacin-treated group (10 mg/kg in drinking water for 5 days), and phytogenic supplementation at low (0.1 g/kg), medium (1 g/kg), and high (10 g/kg) doses. The challenge infection was performed on days 3–4 of age, and fecal samples were collected on days 1, 7, and 42. Microbiome analysis was performed by 16S rRNA gene sequencing and evaluated using microbiome diversity indices and beta-diversity approaches.

Alpha diversity increased over time; however, differences among treatments were already evident in the early post-infection phase. On day 7, diversity was lowest in the enrofloxacin group (Shannon: 1.06), whereas higher diversity was observed with phytogenic supplementation. By day 42, the medium-dose phytogenic group exhibited the most balanced profile (Chao1: 433.8; Shannon: 5.83). At the taxonomic level, by day 7, Proteobacteria and Gammaproteobacteria became dominant in nearly all groups, while by the end of the trial the medium-dose phytogenic supplementation was associated with a shift of the gut microbiome from dysbiosis toward a more balanced community structure. Beta-diversity analyses indicated that the strongest community-level shift was associated with sampling time, which inherently reflected age, while treatment-related differences became more apparent by day 42.

Overall, the phytogenic feed additive modulated the gut microbiome in a dose-dependent manner under infectious pressure, with the medium dose indicating a more favorable restoration of microbiome diversity and community balance. Our findings support the importance of targeted, dose-optimized evaluation of phytogenic strategies within One Health–oriented interventions aimed at reducing antibiotic use.