Hepatopancreatic antioxidant enzyme activities and disease resistance of Pacific white shrimp (Litopenaeus vannamei) fed diet supplemented with garlic (Allium sativum) extract

Abstract

Garlic extract is herbal medicine that stimulate immune systems and disease resistance in many aquatic animals. This study evaluated garlic extract on antioxidant enzyme activity in the hepatopancreas of Pacific white shrimp (Litopenaeus vannamei) fed on diets supplemented with or without extracts of garlic (Allium sativum). Shrimp (8.36±0.17 g) were fed a garlic extract concentration of 2% or 4% for 30 d and then were challenged with Vibrio parahaemolyticus to study growth performance, cumulative mortality, oxidative enzyme activities and hepatopancreatic histopathology. The results showed that shrimp fed a 2% or 4% garlic-extract diet had higher (p < 0.05) survival rates (62% and 60%, respectively) than the control (25%). The hepatopancreas of shrimp was dissected out and analyzed for free-radical-scavenging enzymes, superoxide dismutase (SOD) and catalase (CAT) activity. The garlic-fed shrimp had higher expression of SOD activity compared to the control group (p < 0.05; 21.10, 21.97 and 19.27 units/mL, respective to the 2%, 4% and control group) but the CAT of garlic-extract-fed shrimp had lower (p < 0.05) activity than the control (3.63, 3.64 and 4.76 relative units/mg protein, respective to the 2%, 4% and control group). Histopathological study after challenge revealed atrophy of hepatopancreas cells compared to the control, whereas the hepatopancreas of garlic-fed shrimp was normal with clearly presented B-cells and R-cells. It was concluded that oxidative stress in the hepatopancreas played a major role in the pathogenesis and progression of hepatopancreatic diseases. Moreover, the survival rate of shrimp could be increased by enhancing the oxidative scavenging capacity through diet supplementation using garlic extract.