The effect of Enterococcus faecium L6 and Lactobacillus plantarum L10 combination on broiler growth and protection against enterohemorrhagic Escherichia coli O157:H7 challenge

Following the ban on antibiotic growth promoters in animal diet in China, probiotics have gained prominence as sustainable alternatives in poultry production. This study evaluated the effects of a novel probiotic combination, Enterococcus faecium (E. faecium) L6 and Lactobacillus plantarum (L. plantarum) L10 on both growth performance and protection against enterohemorrhagic Escherichia coli (EHEC) O157:H7 in broilers. A total of 120 one-day-old male white feather broilers were randomly allocated into 4 groups (n = 3 replicates of 10 chicks each): negative control group received basal diet, whereas the Lpro, Mpro, and Hpro groups received the same basal diet supplemented with the probiotics via drinking water at concentrations of 1, 2, and 4 g/L, respectively, from day 1 to 55. In a parallel experiment, 150 broilers were randomly assigned to 5 groups (n = 3 replicates of 10 chicks each) to evaluate protection against EHEC O157:H7 infection. The results demonstrated that probiotics supplementation improved growth performance and carcass yield, and significantly increased the immune organ indices (P < 0.05). Following EHEC O157:H7 challenge, probiotics treated broilers exhibited enhanced immune and antioxidant capacity, as evidenced by increased serum and ileum levels of immunoglobulin A (IgA), IgG, total antioxidant capacity (T-AOC), catalase (CAT), and glutathione peroxidase (GPx), along with reduced malondialdehyde (MDA) levels. In jejunal mucosa, mRNA expression of Occludin, Claudin-1, Claudin-4, ZO-1, and Mucin-2 was significantly increased. 16S rDNA sequencing of cecal contents revealed that probiotics administration enhanced microbial diversity and richness, and increased the relative abundances of Ruminococcus and Streptococcus. The Mpro group showed a marked proliferation of Lactobacillus. These findings demonstrate that combination of E. faecium L6 and L. plantarum L10 not only enhances broiler growth performance but also provides effective protection against EHEC O157:H7 infection, supporting its potency as a viable antibiotic alternative in broiler production.