Thai native chickens show improved growth performance and gut health following supplementation with Lactiplantibacillus plantarum-fermented noni juice.

This study evaluated the dose-dependent effects of Lactiplantibacillus plantarum-fermented noni juice (OLP-FNJ) on growth performance and intestinal physiology in Thai native chickens (Surat Thani strain). A total of 240 birds were randomly allocated to four treatments (0, 2.5, 5.0, and 10.0 mL L-1 OLP-FNJ administered via drinking water) in a completely randomized design and reared for 16 weeks. Growth performance, serum biochemical indices, digestive enzyme activities, intestinal morphology, tight junction-related and immune-related gene expression, and cecal microbiota composition were evaluated. Dose-response relationships were assessed using polynomial regression analysis. OLP-FNJ supplementation exerted a significant linear dose-response reduction in feed conversion ratio over the entire experimental period (3.11 vs. 2.70; linear p < 0.001) and significantly increased body weight gain during the starter phase (280.06 vs. 307.08 g; linear p < 0.05). The greatest numerical responses were observed at 10.0 mL L-1 without adverse effects. Performance enhancement was associated with increased digestive enzyme activities, greater villus height-crypt depth ratios, upregulation of tight junction-related genes, and reduced expression of pro-inflammatory markers. Cecal microbial diversity increased in a dose-dependent manner, accompanied by shifts in dominant bacterial phyla and an elevated Firmicutes-to-Bacteroidetes ratio. Serum biochemical parameters remained within physiological ranges, indicating systemic safety. In conclusion, OLP-FNJ enhanced nutrient utilization efficiency in a dose-dependent manner and was associated with coordinated changes in digestive, structural, barrier, immune, and microbial functions. Fermented noni juice shows potential as a functional drinking-water additive to support sustainable production of Thai native chickens.