Effects of dietary protein and lipid levels on growth, body and plasma biochemical composition and selective gene expression in liver of hybrid snakehead (Channa maculata ♀ × Channa argus ♂) fingerlings

Abstract

An 8-week growth trial was conducted to determine the effects of dietary protein and lipid levels on body and plasma biochemical composition and gene expression in liver of hybrid snakehead (Channa maculata ♀×Channa argus ♂) fingerlings. Ten experimental diets were formulated to contain 34%, 40%, 46%, 52% or 57% dietary crude protein with either 6.5% or 12% crude lipid levels.At the end of the experiment, fish fed higher-protein diets (46%, 52% and 57%) resulted in significantly higher weight gain (WG) compared to those fed the lower-protein treatments (34% and 40%). Dietary protein significantly improved weight gain (P<0.05) except the diet which had higher lipid (12%) and protein levels (57%) and resulted in reduced growth. Also, higher dietary protein levels significantly improved body protein content, morphometrical indices and reduced body lipid. Based on WG, the dietary protein requirements for 95% maximal weight gain was estimated to be 50.5% of dry weight when the lipid level was 6.5% and 47.9% for diets containing 12% lipid. High dietary lipid in the diet did not improve growth performance nor protein utilization significantly but increased fat accumulation in whole body, liver and mesentery, and also caused higher alanine aminotransferase (ALT) activity and greater concentration of cholesterol (CHOL) in plasma. The relative gene expression of target of rapamycin pathway (TOR) gene in liver was significantly improved by increasing dietary protein levels from 34% to 52%, and liver lipoprotein lipase (LPL) gene expression was also increased in the higher-lipid groups. Further research is required to elucidate more details about the regulatory mechanisms of LPL and TOR genes in fish. Statement of relevanceThis study focused on the approximate protein requirement of hybrid snakehead under two different lipid levels using practical feed formula. There is no formal report about the proper protein level in hybrid snakehead feed. These results provide hybrid snakehead feed industry with very valuable information.