The impacts of low fishmeal diet to the antioxidant capacity, endoplasmic reticulum stress, apoptosis and intestinal health of Litopenaeus vannamei as the went on of the feeding trial

Abstract

Plant protein sources are the main alternative to fish meal (FM), but excessive substitution can induce inflammatory responses and oxidative stress in aquatic animals. In this study, the antioxidant capacity, endoplasmic reticulum stress (ERS), apoptosis and intestinal health of Litopenaeus vannamei at the different stages of feeding trial were evaluated after replacing FM with soy protein concentrate (SPC). Two diets were designed: HF diet (25% FM) and LF diet (15% FM + 10% soy protein concentrate), respectively. The samples were collected at 7d, 14d, 28d, 42d, 56d of the feeding trial. The results showed that the antioxidant capacity of the hepatopancreas of shrimp fed the LF diet gradually decreased after 28d. The glutathione peroxidase (GSH-PX) activity, superoxide dismutase (T-SOD) activity and total antioxidant capacity (T-AOC) showed a decreasing trend with the went on of the feeding trial and were lower than those of shrimp fed a HF diet. The length of microvilli and height of mucosal folds in shrimp fed the LF diet were significantly lower than those fed the HF diet after 42d (P<0.05), and the endoplasmic reticulum and mitochondria were swollen, and the mitochondrial matrix showed irregular structure and even almost complete dissolution at 56d. The expression of hepatopancreatic endoplasmic reticulum stress (ERS)-related genes was highest at 14d, and the hepatopancreatic endoplasmic reticulum-related genes were overall higher in shrimp fed the LF diet than those fed the HF diet after 28d. The expression of apoptosis-associated genes in hepatopancreatic cells showed an overall decreasing trend. However, the relative expression of intestinal ERS and apoptosis related gene was in the opposite trend. ERS was enhanced and apoptosis was inhibited in shrimp since 7d of the feeding trial when the dietary FM level was reduced. In conclusion, the antioxidant capacity and immune response of shrimp would be reduced as the feeding trial went on, ERS and apoptosis in the intestine of shrimp fed a LF diet would be earlier to be induced compared to those fed the HF diet.