Growth, serum biochemical, digestive enzyme activities, antioxidant, lipid metabolism and inflammation responses of juvenile hybrid snakehead (Channa maculata♀× Channa argus♂) fed diets with different dietary lipid levels

The study investigated the effects of different dietary lipid levels on the growth, serum biochemical, digestive enzyme activities, antioxidant, lipid metabolism and inflammation responses of juvenile hybrid snakehead ( Channa maculata♀ × Channa argus♂ ). Six different dietary lipid levels (4.70 %, 6.25 %, 8.10 %, 10.35 %, 12.28 %, 14.39 %, labeled as L4, L6, L8, L10, L12, and L14) were prepared as equal protein feed for the experiment. 540 juvenile hybrid snakehead was selected for 63-day culture experiment with an initial weight of (5.31 ± 0.01) g and randomly divided into 6 groups. The results indicated that when the dietary lipid levels ranged from 4.70 % to 10.35 %, the weight gain rate (WGR), specific growth rate (SGR), and protein efficiency ratio (PER) of juvenile hybrid snakehead were significantly increased, while the feed conversion ratio (FCR) was significantly decreased ( P < 0.05 ). The condition factor (CF), and visceral somatic index (VSI) of the fish showed an upward trend. The crude lipid of juvenile hybrid snakehead was significantly increased, while crude protein and moisture was showed the opposite change( P < 0.05 ). The serum levels of plasma cholesterol (CHOL) and high-density lipoprotein cholesterol (HDL-C) were significantly higher than the L14 group compared to the other groups( P < 0.05 ). There was no significant effect on alanine aminotransferase(ALT), aspartate aminotransferase (AST), total protein (TP), triglyceride (TG), low-density lipoprotein cholesterol (LDL-C), and LDL-C/HDL-C ( p > 0.05 ). The ALT in the L14 and L12 groups were significantly higher than the L4, L6, and L8 groups, and the glutathione peroxidase (GSH-Px) of the L12 group was significantly higher than the other groups ( P < 0.05 ). There was no significant effect on liver glycogen, AST, superoxide dismutase (SOD), malondialdehyde (MDA), catalase (CAT), and total antioxidant capacity (T-AOC) ( P > 0.05 ). Furthermore, the expression levels of the mammalian target of rapamycin (mTOR) and acetyl-CoA carboxylase (ACC) in the liver first decreased and then increased, while the peroxisome proliferator-activated receptor α ( PPARα ) showed the opposite phenomenon( P < 0.05 ). There was no significant difference in the fatty acid synthase (FAS) ( P > 0.05 ). The expression of the inhibitory subunit of nuclear factor-kappa B alpha ( IκBα ) in the L4 and L10 groups were higher than those in the L14 group, while the tumor necrosis factor-α ( TNF-α ) and interleukin-8 ( IL-8 ) in the L6 group were significantly lower than those in the L4 group, and the interleukin-10 ( IL-10 ) showed the opposite change( P < 0.05 ). The expression of interleukin-1β ( IL-1β ) in the L6 group was significantly higher than that in the L12 group ( P < 0.05 ). In summary, considering the overall situation, the optimal dietary lipid requirements for juvenile hybrid snakehead is in the ranges of 10.17 % - 11.79 %. • Feed with suitable lipid levels to promote rapid growth of fish. • Provided a new approach for precise nutrition of hybrid snakehead.