Hermetia illucens Larvae Meal Enhances Immune Response by Improving Serum Immunoglobulin, Intestinal Barrier and Gut Microbiota of Sichuan White Geese After Avian Influenza Vaccination

Hermetia illucens Larvae Meal (HILM) has been observed to enhance growth performance and immune function, yet the effects and mechanisms in geese remain less understood. Experiment I included 64 Sichuan White Geese to investigate the optimal additive amount of HILM in diet, and experiment II included 32 Sichuan White Geese to access serum immunoglobulin, spleen immune-related genes, intestinal morphology and gut microbiota at the optimal additive amount of HILM. The results showed that the addition of 1% HILM significantly increased the ADG of Sichuan White Geese (p < 0.05), serum H5-R14 and H7-R4 strain titer at 33 d (p < 0.01) and H5-R13 strain titer (p < 0.05) at 40 d, which is the optimal dose of this trial. Experiment II revealed that the 1% HILM significantly increased serum IgG, IgG1, IgG2a, IgG3 and complement C3 (p < 0.05) and the mRNA expressions of IL-6 (p < 0.05) and CD4 (p < 0.01) in the spleen. The intestinal morphology was improved, and the secretion of SIgA and mRNA expression of Occludin in the jejunum were significantly increased (p < 0.05). Additionally, the abundance of Campilobacterota, Barnesiellaceae and Barnesiella was significantly decreased (p < 0.05), while the abundance of Lactobacillaceae was significantly increased (p < 0.05). This research provides new insights into the use of HILM in geese production.