Comparison effect of dietary astaxanthin and β-carotene in the presence and absence of cholesterol supplementation on growth performance, antioxidant capacity and gene expression of Penaeus monodon under normoxia and hypoxia condition

• Astaxanthin was better than β-carotene as dietary pigment.
• Astaxanthin was better than β-carotene as dietary antioxidant.
• Cholesterol could positively enhance the efficiency of astaxanthin but not β-carotene.

Two trials were conducted to determine the effects of two different carotenoid sources on shrimp, Penaeus monodon, first on growth performance, secondly on the immune response of shrimp was investigated with an air emersion challenge. In trial 1, P. monodon (mean initial wet weight about 2.07 g) were fed five diets in triplicate; a basal diet (D1) without carotenoids; two diets formulated to supply 0.1% astaxanthin alone (D2), combination of 0.1% astaxanthin and 1% cholesterol (D3); two diets with 0.25% β-carotene alone (D4), combination of 0.25% β-carotene and 1% cholesterol (D5). Growth performance (final body weight, FBW; weight gain, WG; biomass gain, BG) and survival of shrimp fed D3 showed the highest values. The apparent digestibility coefficients (ADCs) of carotenoids in carotenoid-supplemented diets (D2–D5) were quietly high (> 90%), and cholesterol supplementation did not significantly improve the carotenoid ADCs any more. However, cholesterol addition significantly enhanced the tissue carotenoid retention efficiencies in astaxanthin-supplemented diet treatments (D3 vs D2) but not in β-carotene-supplemented diet treatments (D5 vs D4). Hepatopancreas malondialdehyde (MDA) and hemolymph clotting time of shrimp fed carotenoid-supplemented diets (D2–D5) were lower (P < 0.05) than those of shrimp fed the basal diet (D1). On the contrary, total hemocyte count of shrimp fed the basal diet (D1) was lower (P < 0.05) than that of shrimp fed carotenoid-supplemented diets (D2–D5). No significant differences (P > 0.05) were found in expression profiles of heat shock protein 70 (Hsp 70) mRNA and hypoxia inducible factor-1α (HIF-1α) mRNA in hepatopancreas of shrimp among all diet treatments. In trial 2, the shrimp were exposed to air during a simulated live transportation for 36 h after the rearing trial 1. No mortalities were observed in all diet treatments after 36 h of simulated live transportation. Total hemocyte counts of shrimp fed the basal and β-carotene-supplemented diets (D1, D4 and D5) significantly declined (P < 0.05) after trial 2 while it remained unchanged in shrimp fed astaxanthin-supplemented diets (D2 and D3). The hemolymph clotting time of shrimp fed the basal diet (D1) significantly increased (P < 0.05) after trial 2 and it was unchanged in the shrimp fed the carotenoid-supplemented diets (D2–D5). MDA and carbonyl protein contents of hepatopancreas of shrimp in trial 2 were the higher (P < 0.05) levels record compared to contents in trial 1. Expression profiles of Hsp 70 mRNA and HIF-1α mRNA of hepatopancreas of shrimp fed the basal diet were significantly lower (P < 0.05) than those of shrimp fed other diets. In conclusion, all the data suggested that astaxanthin was better than β-carotene either as dietary pigment or as dietary antioxidant in the commercial diet of P. monodon, and the supplement of cholesterol could positively enhance the efficiency of astaxanthin but not β-carotene.