Ostrich-derived Bacillus safensis O-6 enhances broiler growth performance by modulating gut microbiota and protein digestibility.

In broiler production, the inefficient utilization of dietary protein limits growth performance and wastes resources. Inspired by the high feed conversion efficiency of ostriches, which may host beneficial digestive microbes, this study investigated whether fecal microbiota transplantation (FMT) from ostriches could confer advantageous traits to broilers, and further sought to isolate and evaluate potential probiotic. In an initial FMT trial involving 54 one-day-old broilers, the FMT group exhibited significantly higher average daily gain (ADG) at 7 and 14 days of age compared to the Ctrl group (P < 0.05). From the fecal samples of ostrich donors, a bacterial strain, Bacillus safensis O-6 (O-6), was isolated and identified as a high producer of both protease and cellulase. In a subsequent feeding trial with 72 one-day-old broilers, supplementation with O-6 (4.74 × 10⁷ CFU/mL/day in drinking water) increased the ADG by 7.16% by day 35 (P <0.01). The treatment also significantly enhanced the activities of protease, amylase, and lipase in the small intestine (P < 0.05), elevated serum immunoglobulins A and M (IgA and IgM) (P < 0.01), and improved immune organ indices (Spleen index and Bursa of Fabricius index, P < 0.05). Furthermore, O-6 supplementation significantly enhanced the alpha and beta diversity of the cecal microbiota (P < 0.05). This was accompanied by an enrichment of beneficial bacterial taxa, including Rikenellaceae and Alistipes, alongside a substantial reduction in cecal protein content by 28.23%, indicating improved protein digestibility. These results demonstrate that O-6 is a promising probiotic that enhances broiler growth by improving digestive enzyme activity, immune function, and gut microbiota structure. This study demonstrates that beneficial traits of ostriches can be transferred to broiler chickens through their gut microbiota (probiotics), offering a new avenue for the exploration of avian-derived probiotics.