Effects of dietary starch levels on growth, immune function, insulin receptor expression, and tyrosine kinase activity in GIFT tilapia

This study aimed to explore the effects of graded dietary starch levels on growth performance, immune status, as well as insulin receptor expression and tyrosine kinase activity in GIFT tilapia. Three experimental dietary treatments were set up in this trial, including a low-starch group (LS), medium-starch group (MS), and high-starch group (HS). Each treatment contained four replicates, with 30 fish per replicate. The experimental fish were reared in a temperature-controlled recirculating aquaculture system for 49 days. The results showed that the high-starch diet suppressed fish growth, elevated whole-body crude fat content, and significantly altered serum biochemical parameters including alanine transaminase, aspartate transaminase, cholesterol and triglyceride levels. Meanwhile, muscle tyrosine kinase activity was markedly upregulated in fish fed the high-starch diet. The medium-starch diet upregulated the mRNA expression of insulin receptor 1(IR-1) in muscle and hepatic tissues, whereas the high-starch diet downregulated hepatic and muscle IR-1 mRNA expression. In conclusion, GIFT tilapia exhibits a high tolerance to dietary starch. Accordingly, appropriately reducing dietary protein levels while adopting a suitable starch proportion in feed formulation can maintain favorable growth performance and immune status in GIFT tilapia.