Effect of treatment with NZ9000 on intestinal microbiota and mucosal immune responses against in broiler chickens.

Alterations in intestinal microbiota can modulate the developing avian intestinal immune system and, subsequently, may impact on resistance to enteric pathogens. The aim was to demonstrate that early life exposure to , could affect either susceptibility or resistance of broilers to necrotic enteritis (NE). NZ9000 () pre-treatment at 1, 7, 14 and 21 days of age (DOA) led to a significant decrease in NE lesion scores in infected chickens. Infection was associated with spatial and temporal decreases in mononuclear phagocytes and CD4+ αβ T cells. However, pre-treatment and subsequent infection led to a significant increase in mononuclear phagocytes, CD8α + γδ T, αβ T cells (CD4+ and CD8α+) and B cells (IgM+, IgA+ and IgY+), as well as IL-12p40, IFN-γ and CD40. Differential expression of interleukin (IL)-6, IL-8, IL-10, IL-13, IL-18, IL-22, and transforming growth factor (TGF)-β were observed in treated chickens when compared to infected chickens. Microbiota analysis in infected chickens demonstrated an increase in abundance of Bacillota, Bacteroidota, Pseudomonadota and Actinomycetota. These findings suggests that modulation of the chicken intestinal immune system by confers partial protection 30 against NE.