Dietary supplementation of astaxanthin increased growth, colouration, the capacity of hypoxia and ammonia tolerance of Pacific white shrimp (Litopenaeus vannamei)

Astaxanthin (AX) is a naturally occurring carotenoid often used as a dietary supplement in the Pacific white shrimp (Litopenaeus vannamei) culture industry. This study evaluated the effects of chemically synthesized astaxanthin on growth performance, survival, stress resistance, immune responses, and pigmentation of the Pacific white shrimp fed diets supplemented with five dietary levels of AX containing 0, 20, 40, 80, and 160 mg kg(-1). The feeding trial was conducted for 8 weeks. The results showed the individuals fed diets supplemented with AX exhibited better growth performance, whose final body weight (FBW), body weight gain (BWG), specific growth ratio (SGR), and Myostatin (MSTN) showed a dose-dependent increase in Astaxanthin levels. Following acute hypoxia and ammonia stress test, the survival rate (SR) of shrimp fed with 40, 80 and 160 mg kg(-1) diets were higher than that of the control group. AX diet groups improved their capacity of antioxidant defense to prevent oxidative damage, including increasing the activities of acid phosphatase (ACP), total antioxidant capacity (T-AOC), and decreasing the activities of superoxide dismutase (SOD) and catalase (CAT), the content of malondialdehyde (MDA) compared to the control group. In addition, the gene expression of various antioxidant enzymes in the hepatopancreas of shrimp was significantly upregulated higher such as manganese superoxide dismutase (MnSOD) and glutathione S-transferase (GST). High expression of hypoxia-inducible factor-1 alpha (HIF1 alpha) and glutamate dehydrogenase (GDH-beta), glutamine synthetase (GS) in 80 and 160 mg kg(-1) group indicated their effect on glycolysis possibly, which is vital on energy production required. Quadratic regression analysis indicated that the optimal levels for growth and pigmentation were 126.94 mg kg(-1) and 138.96 mg kg(-1) diet, respectively. In conclusion, Astaxanthin can enhance growth performance, alleviate oxidative and ammonia stress, improving the immunity of Pacific white shrimp.