Abstract: To evaluate the effects of yellow mealworm meal (YM) as a partial replacement for soybean meal (SBM) on the hepatic and intestinal health of fish, four groups of isonitrogenous (320 g/kg crude protein) and isoenergetic (16.8 MJ/kg) experimental diets were formulated using YM to replace 0, 15%, 30%, and 45% SBM in an SBM-based diet for Nile tilapia (Oreochromis niloticus). A ten-week feeding experiment was conducted and the parameters related to the hepatic and intestinal health were analyzed. The results indicated that YM could replace 15% SBM in tilapia feed without negative effects on the hepatic and intestinal health. However, when the replacement ratio was up to 30%, decreased intestinal muscular thickness, shorter intestinal villi, lower intestinal transepithelial electrical resistance and higher mRNA expression level of tight junction protein-related genes were observed. When the replacement ratio was up to 45%, the intestinal injury was further exacerbated, and hepatic injury occurred. Hepatic injury was manifested by a significant increase in serum alanine transaminase activity, blurred hepatocyte boundaries, lipid droplet accumulation, and a significant increase in total lipids, triglycerides, non-esterified free fatty acids, and glycogen content. Transcriptome analysis revealed that genes related to glycogen synthesis and apoptosis were significantly enhanced in liver in YM45. Further analysis revealed thatklf9, an oxidative stress-related gene, was significantly upregulated in both liver and intestine, suggesting that oxidative stress occurred in YM45 group.

Key words: insect meal, soybean meal replacement, Tenebrio molitor, hepatic and intestinal health, tilapia