Dietary enzyme-hydrolyzed marine proteins supplementation promotes appetite, enhances lipid and protein metabolism in Litopenaeus vannamei fed reduced fish meal diets

An 8-weeks feeding trial was conducted to evaluate the effect of dietary enzyme-hydrolyzed marine protein (EMP) supplementation on appetite, protein and lipid metabolism of Litopenaeus vannamei fed reduced fishmeal diets. The control group was supplemented with 30 % fishmeal, in the experimental group, 28 % fish meal was supplemented with 1 % EMP (1 % EMP), and 26 % fish meal with 2 % EMP (2 % EMP). The results showed that there were no significant differences in growth performance in each group (P > 0.05). Shrimp in control group exhibited higher total cholesterol, triglyceride and low-density lipoprotein cholesterol in hemolymph than those in the other groups (P < 0.05). The results of intestinal histology showed that shrimp fed with 1 % EMP diet exhibited higher fold height and fold width than those fed the other diets (P < 0.001). Compared with control group, the lipid catabolism genes and regulatory factors (atgl, hsl, ampkα, ampkγ, acox1) was significantly enhanced in 1 % EMP group (P < 0.05). Moreover, the neurotransmitter and appetite related-genes expressions (such as oa-ta, tdc, tbh and ghs-r1) in 1 % EMP group of cerebral ganglion were significantly up-regulated than those in other group (P < 0.05). Dietary 1 % EMP supplementation activated expressions of TORC1 pathway-related genes (tor, rheb, slc3a2, 4e-bp) in the hepatopancreas than those feed the control diet (P < 0.05). In conclusion, the results revealed that reducing 2 % fish meal and adding 1 % EMP in the diet could improve the appetite, lipid and protein metabolism, intestinal and hepatopancreas health of juvenile Pacific white shrimp.