The Effect Of Dietary Cholesterol On The Growth,molting And Antioxidant Ability Of Procambarus Clarkii

In order to study the suitable cholesterol content in the dietary of Procambarus clarkii,and to reveal the regulation mechanism of cholesterol on the growth and molting,five diets with different levels of supplemented cholesterol(0,0.25,0.50,0.75,and 1.00%),which were analyzed to contain 0.06,0.29,0.54,0.81,and 1.05%cholesterol,were designed and used in the presented study.After the conditioning period,a total of 225 P.clarkii with similar sizes(initial weight = 4.4 ± 0.1 g)were randomly divided into 15 tanks.And then the P.clarkii in each tank labeled five groups(C0.00,C0.25,C0.50,C0.75 and C1.00,respectively)with three replications were fed with one of five experimental diets for 45 days.After the feeding trial,samples were collected and tested.The results were obtained as follows:The survival rate of Procambarus clarkii showed no significant difference(P >0.05)among all groups.The weight gain rate,specific growth rate and average molting times increased significantly(P < 0.05)as the cholesterol level increased from 0 to0.54%,but then significantly decreased as the cholesterol content level increased from0.54 to 1.05%.The feed coefficient of C0.50 group was the lowest,while the meat content of C0.50 group was the highest(P < 0.05)among all groups.Fatness and index of liver-bodyweight increased significantly(P < 0.05)as the cholesterol content level increased from 0.00 to 1.05%.There was no significant difference in moisture,crude protein,crude ash and calcium content of Procambarus clarkii(P > 0.05)among all proups.The whole-body crude fat content in C0 and C0.25 group was significant lower compared to C0.5,C0.75 and C1.0 groups.Alanine aminotransferase(ALT)level in C0.75 groups was significant high than that in C0,C0.5and C0.75 groups,but lower than that in C1.0 group.Aspertate aminotransferase(AST)level in C0,C0.25 and C0.75 groups was significant high than that in C0.5 group,but lower than that in C1.0 group.The level of cholesterol in dietary has no significant effect on serum albumin(P > 0.05).Globulin level in group C0.5 was significantly higher than that in group C0(P < 0.05),and there was no significant difference in other groups(P > 0.05).According to the comprehensive analysis of body index,growth performance,body composition and blood biochemical index,the optimal dietary content of cholesterol of Procambarus clarkii is 0.53%-0.54%.Chitinase m RNA expression and hemolymphatic LDL-C content significantly increased(P < 0.01)as the cholesterol content level increased from 0 to 0.54%,and then significantly decreased(P < 0.05)as the cholesterol content level increased from0.54 to 1.03%.P.clarkii fed with 0.25% cholesterol content and without cholesterol content had significantly higher MIH expression level compared to P.clarkii fed with0.54 and 0.75% cholesterol content.Total cholesterol content in the hemolymph,hepatopancreas,and intestine,as well as hemolymphatic HDL-C content of P.clarkii increased significantly as the cholesterol content increased from 0 to 1.05%.Superoxide dismutase(SOD)and catalase(CAT)activities significantly increased(P < 0.05)as the cholesterol content level increased from 0 to 0.54%,and then significantly decreased(P <.05)as the cholesterol content level increased from 0.54% to 1.05%,while the result of malondialdehyde(MDA)content showed an opposite trend.Glutathione(GSH)activities in C0,C0.5 and C0.75 groups were significant high than that in C0 and C1.0 groups,but lower than that in C0.25 group.From the comprehensive analysis of molting,digestive ability and immune indexes,the appropriate cholesterol content can promote the accumulation of nutrients,molting and immune performance in P.clarkii.Sterol regulatory element binding proteins-1(srebps-1),which is responsible for the biosynthesis of fatty acids,triglycerides and cholesterol,is critical for regulating lipid symthesis.In the presented study,RNA was extracted from hepatopancreas of Procambarus clarkii,and ORF full-length sequence of srebp-1 gene was amplified and spliced by RACE.The sequence length was 3610 bp,including 369 bp in non-coding region and 3241 bp in coding region,encoding 1079 amino acids.Sequence alignment results showed that the homology of Procambarus clarkii with Scylla paramamosain and Penaeus vannamei was high.By constructing phylogenetic tree,it was found that the relationship between Procambarus clarkii and Scylla paramamosain was the closest and conservative in evolution,while the homology with other fish was low.Conclusion: The optimal dietary content of cholesterol for Procambarus clarkii was 0.53%-0.54%.The appropriate cholesterol supplementation could promote molting and improve the immune function of Procambarus clarkii.Excessive cholesterol had no effect on molting,but reduced the antioxidation activity.srebp-1 gene of Procambarus clarkii was 3610 bp long and encoded 1079 amino acids.