Effects of Astaxanthin on Growth,Body Color,Skin Pigment,and Antioxidant Capacity of Epinephelus akaara
[Objective]To explore the effects of astaxanthin on growth,body color,skin pigment,and antioxidant activity of red-spotted grouper(Epinephelus akaara),and to provide scientific basis for the application of astaxanthin in the feed of red-spotted grouper.[Method]0,100,200,400 and 800 mg/kg astaxanthin were added to the basic diets of red-spotted grouper,and 5 kinds of iso-nitrogen and iso-lipid diets were prepared,which were recorded as the group AST0(control),AST100,AST200,AST400 and AST800,respectively.The fish with initial body mass(BM)of(6.17±0.26)g and total length of(7.84±0.54)cm were fed on the diets for 90 days.The growth performance indexes of the grouper were measured.The body color parameters of the grouper were measured by colorimeter.The concentrations of carotenoids and melanin in the skin of the grouper were determined by one-step sandwich technique enzyme linked immunosorbent assay(ELISA).The total antioxidant capacity(T-AOC)of liver and other antioxidant properties of the grouper were measured by a kit.[Result]Compared with AST0 group,there were no significant differences in body mass(BM),weight gain rate(WGR),specific growth rate(SGR),survival rate,feed conversion ratio and condition factor in all experimental groups(P>0.05),while hepatosomatic index in AST800 group was significantly decreased(P<0.05).With the increase of astaxanthin in the diet,the skin spots on the head,side and tail of the fish become orange-yellow,and the base of the ventral fins become dark red.The density of pigmented cells in dorsal fin,anal fin and tail fin was high,while the density of pigmented cells in pectoral fin and ventral fin was low.Adding 100 mg/kg or more of astaxanthin in the diet can increase the number of xanthophores and erythrophores in the ventral fins of red-spotted grouper.The brightness(L*)of operculum skin,dorsal skin,caudal peduncle skin,pectoral fin and dorsal fin of AST100,AST200,AST400 and AST800 groups were significantly higher than that of AST0(P<0.05),the redness(a*)of operculum skin and dorsal fin was significantly higher than that of AST0,and the yellowness(b*)of operculum skin,dorsal skin,ventral skin,caudal peduncle skin,pectoral fin,dorsal fin and caudal fin were significantly increased compared with AST0(P<0.05).Dietary astaxanthin significantly increased the carotenoid concentration in the back and ventral skin and the melanin concentration in the ventral skin(P<0.05).The activities of T-AOC,catalase,superoxide dismutase and glutathione peroxidase in liver of red-spotted grouper were significantly increased with the increase of dietary astaxanthin supplemental level(P<0.05),and the content of malondialdehyde was significantly decreased with the increase of dietary astaxanthin supplemental level(P<0.05).[Conclusion]Dietary astaxanthin had no significant effects on BM,WGR and SGR,but significantly improved body color and internal pigmentation,and increased liver antioxidant capacity.Based on the experimental data of growth,body color,skin pigment content and antioxidant activity,the optimal supplemental level of astaxanthin in the diet of red-spotted grouper is 200-400 mg/kg.
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