Response characteristics of defatted mealworm (Tenebrio molitor) instead of fish meal to the intestinal immunity and microbiota of juvenile pikeperch (Sander lucioperca)

The aim of this study was to investigate the impact of varying levels of defatted mealworm as a substitute for fishmeal on the growth, intestinal health, and gut microbiota of juvenile pikeperch. The results showed that the MW25 group achieved the highest weight gain rate and specific growth rate, with no significant difference from the MW0 group. Moreover, the MW25 group exhibited the lowest feed conversion ratio. This group also demonstrated the highest trypsin activity, while lipase activity remained unchanged across all treatment groups. Intestinal villus height and width were not significantly affected by mealworm inclusion. These findings suggest that the inclusion of mealworm did not impact the digestive and absorptive capacity of the pikeperch intestine. However, gene expression related to growth showed a consistent decline as mealworm inclusion increased. Additionally, increasing mealworm levels led to a reduction in gut microbiota diversity and abundance, with a decreased presence of Staphylococcus and Lactobacillus, which negatively affected the intestinal microbiota structure.