Effect of oral administration of microcin Y on growth performance, intestinal barrier function and gut microbiota of chicks challenged with Salmonella Pullorum

The lasso peptide microcin Y (MccY) effectively inhibits various serotypes of Salmonella in vitro, but the antibacterial effect against S . Pullorum in poultry is still unclear. This study was the first to evaluate the safety and anti- S . Pullorum infection of MccY in specific pathogen-free (SPF) chicks. The safety test showed that the body weight, IgA and IgM levels of serum, and cecal microbiota structure of 3 groups of chicks orally administrated with different doses of MccY (5 mg/kg, 10 mg/kg, 20 mg/kg) for 14 days were not significantly different from those of the control group. Then, the chicks were randomized into 3 groups for the experiment of anti- S . Pullorum infection: (I) negative control group (NC), (II) S . Pullorum-challenged group (SP, 5 × 10 8 CFU/bird), (III) MccY-treated group (MccY, 20 mg/kg). The results indicated that compared to the SP group, treatment of MccY increased body weight and average daily gain ( P < 0.05), reduced S . Pullorum burden in feces, liver, and cecum ( P < 0.05), enhanced the thymus, and decreased the spleen and liver index ( P < 0.05). Additionally, MccY increased the jejunal villus height, lowered the jejunal and ileal crypt depth ( P < 0.05), and upregulated the expression of IL-4 , IL-10 , ZO-1 in the jejunum and ileum, as well as CLDN-1 in the jejunum ( P < 0.05) compared to the SP group. Furthermore, MccY increased probiotic flora ( Barnesiella , etc.), while decreasing ( P < 0.05) the relative abundance of pathogenic flora ( Escherichia and Salmonella , etc.) compared to the SP group.