Low-Protein-Fed Chickens Benefit from Probiotic L. salivarius and L. johnsonii on Performance and Microbiota

This study aimed to evaluate the combined effects of two probiotic strains, <i>Lactobacillus salivarius</i> TRM58163 and <i>Lactobacillus johnsonii</i> TRM59525-originally isolated from human infant feces (aged 0-6 months)-on growth performance, antioxidant capacity, liver function, intestinal morphology, and cecal microbiota in 100-day-old Baicheng You chickens fed a low-protein diet. Ten strains isolated from infant feces were initially screened, and eight were assessed in vitro for safety, gastrointestinal tolerance, and antimicrobial activity. TRM58163 and TRM59525 showed the best probiotic potential. A total of 240 Baicheng You chickens (100 days old) were randomly assigned to two groups: The control group was fed a low-protein diet (CLD), while the experimental group had <i>Lactobacillus salivarius</i> TRM58163 and <i>Lactobacillus johnsoni</i> TRM59525 added to the low-protein diet (LLD, ≥1 × 10⁹ CFU/g feed). Each treatment included four replicates of 30 chickens over 42 days. Probiotic supplementation significantly improved average daily feed intake (ADFI), average daily gain (ADG), and feed conversion ratio (FCR) (<i>p</i> < 0.05). It also enhanced antioxidant status, with increased plasma superoxide dismutase activity and reduced malondialdehyde levels. Lower total bilirubin levels indicated improved liver function. The LLD group showed increased ileal villus height and villus-to-crypt ratio. 16S rRNA gene sequencing revealed greater microbial diversity, increased beneficial genera (e.g., <i>Akkermansia</i>, <i>Bacteroides</i>), and decreased harmful taxa (e.g., <i>Sutterella</i>). These microbial shifts were associated with improved growth and metabolic profiles. In conclusion, <i>L. salivarius</i> TRM58163 and <i>L. johnsonii</i> TRM59525 supplementation improved performance, gut health, and microbial composition, supporting their use as functional probiotics in low-protein poultry diets.