Comparative evaluation of Saccharomyces, Bacillus, and Lactobacillus as antibiotic alternatives on growth performance, redox balance, and gut microbiota in broilers

Abstract

Abstract This study evaluated the efficacy of Saccharomyces cerevisiae (SC), Bacillus subtilis (B), Lactobacillus casei (LB), and their combination (Mix) as natural alternatives to antibiotics in broiler nutrition. Liquid cultures were prepared to a density of 10⁸ CFU/mL and examined morphologically by light microscope and scanning electron microscopy. Three hundred one-day-old Arbor Acres broiler chicks were randomly allocated to five groups: a control (basal diet) and four groups receiving 900 ppm of B, LB, SC, or Mix from day 11 to day 33, using a completely randomized design with six replicates per treatment. Growth performance, antioxidant indices, thyroid hormones, and intestinal microbiota were assessed. Dietary supplementation with B, LB, SC, or Mix significantly improved body weight gain and feed conversion ratio compared with the control. In addition, enhanced total antioxidant capacity and catalase activity, along with reduced MDA levels, indicated improved oxidative status. Probiotic supplementation increased intestinal Lactobacillus counts, suppressed Salmonella spp., and reduced total bacterial count. Moreover, no adverse effects were observed on thyroid hormones or liver and kidney function indicators. These findings suggest that the tested probiotics are effective antibiotic alternatives for improving broiler health, productivity, and gut microbial balance. The combined probiotic treatment improved several evaluated parameters, supporting sustainable poultry production practices.