Synbiotic Potential of Pediococcus acidilactici V202-Fermented Rice Bran: In Vitro and In Vivo Effects on Nutrient Digestibility and Cecal Microbial Populations in Aged Laying Hens

To sustain egg production and gut health in aging flocks, the poultry industry seeks alternative synbiotic feed supplements. This study aimed to optimize Pediococcus acidilactici V202-fermented rice bran (PFR) and evaluate its effects on nutrient digestibility and cecal microbial populations in aged laying hens. In experiment 1, solid-state fermentation conditions (substrate particle size, moisture, and temperature) were optimized for viable lactic acid bacteria (LAB) counts. In experiment 2, in vitro assays were used to assess cecal fermentation kinetics. Subsequently, an in vivo trial involving twenty 80-week-old Hy-Line Brown hens evaluated the impact of PFR supplementation on nutrient digestibility and microbial profiles compared to a control diet. For experiment 1, the optimized fermentation conditions consisted of 40-mesh rice bran, a 30:70 bran-to-water ratio, incubation at 39 °C for 12 h, and drying at 40 °C, which produced the highest viable LAB counts. For experiment 2, PFR enhanced in vitro cumulative cecal gas production. In vivo, compared to the control, PFR supplementation significantly increased the apparent digestibility of dry matter (82.69% vs. 77.03%; p = 0.014), crude protein (82.75% vs. 75.38%; p = 0.016), crude fiber (36.30% vs. 23.10%; p = 0.015), ether extract (86.70% vs. 82.91%; p = 0.016), and gross energy (78.31% vs. 74.99%; p = 0.026). Furthermore, PFR beneficially modulated cecal microbial populations, increasing LAB while reducing Salmonella spp. In conclusion, these findings suggest that optimized PFR could be a promising synbiotic supplement to improve digestive efficiency and support beneficial cecal microbial populations in aged laying hens.