Comparison Of Coloring Effect Of Dietary Astaxanthin Sources And Improvement Of Astaxanthin Deposition In Diets Of Rainbow Trout (Oncorhynchus Mykiss)

Exp.1 Dietary A.aestivalis Extract Improved the Flesh Pigmentation and Antioxidation of Rainbow TroutThis study investigated the effects of Adonis aestivalis extract on the pigmentation and antioxidation of rainbow trout.Five isonitrogenous and isolipidic diets were designed as the control diet and the supplementation of 1.7,3.4,6.8 g/kg A.aestivalis extract（with astaxanthin inclusion of 50,100 and 200 mg/kg）and 1.0 g/kg synthetic astaxanthin product（with astaxanthin inclusion of 100 mg/kg）in the control diet,respectively.Then the five diets were fed to rainbow trout（6.27±0.04 g）for 6 weeks.Compared to the control group,the supplementation of A.aestivalis extract significantly increased the redness（a*）and yellowness（b*）,and decreased the flesh drip loss at the4^th and 6^th h（P<0.05）.The redness（a*）and the astaxanthin content in flesh,skin and liver of rainbow trout fed 3.4 g/kg A.aestivalis extract diet reached the similar levels to the fish fed synthetic astaxanthin diet（P>0.05）.T-SOD and MDA in flesh and serum were significantly decreased,and the inhibition ability of–OH was significantly increased in all the astaxanthin-supplemented groups（P<0.05）.The above three indexes of 3.4 g/kg and 6.8 g/kg extract groups showed the similar levels to the synthetic astaxanthin group（P>0.05）.In conclusion,dietary A.aestivalis extract effectively improved the flesh color and the antioxidant capacity of rainbow trout,and the supplemental level was suggested to be 3.4 g/kg with astaxanthin inclusion of 100mg/kg diet.Exp.2 Effects of Astaxanthin Sources on Growth Performance,Flesh Pigmentation and Antioxidation of Rainbow TroutThis study investigated the effects of astaxanthin sources on the growth performance,flesh pigmentation and antioxidation of rainbow trout.Five isonitrogenous and isolipidic diets were designed as the control diet and the astaxanthin sources supplemented diets,including 1.0 g/kg synthetic astaxanthin product（Ast）,6.5 g/kg Adonis aestivalis flower（AF）,3.4 g/kg Adonis aestivalis extract（AE）and 4.4 g/kg Haematococcus pluvialis extract（HE）with the same astaxanthin inclusion of 100mg/kg.Then the five diets were fed to rainbow trout（6.28±0.07）g for 6 weeks.The supplementation of A.aestivalis flower significantly decreased weight gain（WG）and increased feed conversion ratio（FCR）of rainbow trout（P<0.05）.The flesh redness（a*）,yellowness（b*）,tissue astaxanthin content and the serum carotenoid content(except the AF group at the 2^nd week)of the rainbow trout fed the four astaxanthin sources supplemented diets were significantly higher,and the flesh lightness（L*）was significantly lower than those of the control group（P<0.05）.Compared to the control group,the supplementation of synthetic astaxanthin,A.aestivalis extract and Haematococcus pluvialis extract significantly decreased the flesh thawing loss,drip loss at the 4^thand 6^thh（P<0.05）,reduced the T-SOD and MDA in flesh,liver and serum,and the inhibition ability of–OH was significantly increased（P<0.05）.In conclusion,the supplementation of A.aestivalis extract and Haematococcus pluvialis extract in diet effectively improved the flesh pigmentation and antioxidant capacity of rainbow trout,and reached the similar effects to synthetic astaxanthin,while Adonis aestivalis flower was not suggested to be used in the diet of rainbow trout.Exp.3 Effects of Dietary Emulsifier and Antioxidant on the Deposition of Astaxanthin for Rainbow TroutThis study investigated the effects of different emulsifiers and antioxidants on the deposition of astaxanthin in the diet of rainbow trout.Six isonitrogenous and isolipidic diets were designed to feed rainbow trout（6.69±0.02）g for 6 weeks.The six diets were the control diet,0.5 g/kg and 1.0 g/kg synthetic astaxanthin supplemented diets containing pure astaxanthin of 50 mg/kg and 100 mg/kg（AST-500,AST-100）,and 0.6g/kg sodium taurocholate（ST）,0.1 g/kg tea polyphenol（TP）and 0.1 g/kg surfactin（SUR）supplemented diets based on the AST-50 diet with effective contents of 400mg/kg ST,100 mg/kg TP and 100 mg/kg SUR,respectively.Skin astaxanthin content in all astaxanthin supplemented groups was significantly higher than that in the Con group（P<0.05）,and no difference was observed among these groups（P>0.05）.The addition of ST,TP and SUR in AST-50 diet significantly increased the flesh redness（a*）,yellowness（b*）,and the astaxanthin content in flesh and liver（P<0.05）,which were still lower than those in the AST-100 group（P<0.05）.The flesh thawing loss and T-AOC in flesh,serum and liver of TP and SUR groups were significantly higher than those of the Con group,but lower than those of the AST-100 group.T-SOD showed an opposite trend（P<0.05）.ST group showed the similar levels of antioxidant indexes to AST-50 group（P>0.05）.In conclusion,the supplementation of tea polyphenols and surfactin in the diet containing low astaxanthin content could effectively improve the deposition of astaxanthin and the antioxidant capacity of rainbow trout;Sodium taurocholate also promoted the deposition of astaxanthin,but did not significantly affect the antioxidant ability.