The study investigated the potential of a novel probiotic candidate, Lactobacillus casei FA23, as an alternative to antibiotics in poultry nutrition. Out of 45 isolates, L. casei FA23 was selected based on its superior antimicrobial activity and was identified using MALDI-TOF MS. The selected isolate demonstrated strong probiotic properties, including high tolerance to simulated gastrointestinal conditions (89.6% viability at pH 2.5 and 0.3% bile salts), pronounced auto-aggregation (71.2%), and notable cell-surface hydrophobicity (58.3%) (P<0.05). In vitro, L. casei FA23 exhibited potent antioxidant capacity (IC₅₀ = 100µg/mL; p<0.05) and broad-spectrum antimicrobial activity against significant poultry pathogens, with MICs of 50µg/mL of cell-free extract against Staphylococcus aureus and Candida albicans. In a 42-day trial involving Japanese quail, dietary supplementation with L. casei FA23 (50–250mg/kg feed) substantially enhanced growth compared to control and antibiotic performance (P<0.05). At a dosage of 200mg/kg, responses were comparable to those of chlortetracycline, with a higher final body weight (250.3 vs. 235.2g), an improved feed conversion ratio (2.95 vs. 3.18), and reduced mortality (P<0.05). Supplementation improved serum biochemistry (organ function and lipid profile), humoral immunity (IgG, IgM), and systemic antioxidant status (P<0.05). At the molecular level, L. casei FA23 upregulated genes related to the intestinal barrier (Occludin, MUC2), innate defense (AvBD6, lysozyme), and nutrient transport (SGLT1), while downregulating IL 1β (P<0.05), indicating improved gut integrity and reduced inflammation. Meat quality was enhanced by higher protein content, lower fat content, better water-holding capacity and tenderness, and decreased TBARS and TVBN (P<0.05). Cecal microbiota shifted toward a healthier profile, with lower overall bacterial and fungal counts and increased lactic acid bacteria. Overall, L. casei FA23 is a potent, multifunctional probiotic and a promising natural alternative to in-feed antibiotics in quails.

To Cite This Article: Alqahtani FS, 2026. The influence of Lactobacillus casei FA23 as probiotic and feed additive on enhancing growth, health, gut integrity, cecal microbiota, and meat quality in Japanese quails. Pak Vet J, 46(3): 595-605. http://dx.doi.org/10.29261/pakvetj/2026.048