克氏原螯虾幼虾对饲料维生素A需求量的研究OA

This study aimed to investigate the effects of dietary vitamin A and determine its requirement of juvenile red swamp crayfish(Procambarus clarkii).Six isonitrogenous,isolipidic,and isoenergetic experimental diets were formu-lated with analyzed vitamin A potencies of 11573(A1),20042(A2),26274(A3),37818(A4),55159(A5),and 79200(A6)IU/kg,respectively.These diets were fed to crayfish with an initial average body weight of(3.40±0.01)g for 8 weeks.The results revealed that weight gain rate and specific growth rate were significantly higher in groups A4 and A5 compared to the control group(A1)(P＜0.05),with the highest values observed in group A4.In contrast,feed conversion ratio and hepatosomatic index were significantly decreased(P＜0.05),reaching the lowest values in group A4.Compared to the control group,the total antioxidant capacity,catalase,and superoxide dismutase activities in the hepatopancreas were significantly enhanced(P＜0.05)in group A4.Serum aspartate aminotransferase and alanine aminotransferase activities decreased initially and then increased with rising vitamin A levels,both attaining their mini-mum in group A4.Simultaneously,the incidence of B-cells and R-cells in the hepatopancreas,intestinal villi length and width,and activities of hepatopancreatic trypsin,amylase,lipase,and intestinal trypsin were significantly elevated in group A4(P＜0.05).Furthermore,group A4 significantly up-regulated the gene expression levels of Chitinase,EcR,and RXR in the hepatopancreas,while significantly down-regulating the expression of MIH(P＜0.05).In conclusion,opti-mal vitamin A supplementation improve digestive function,enhance hepatopancreas antioxidant and immune capacity,and regulate ecdysis-related gene expression,thereby promoting growth performance in P.clarkii.Based on broken-line regression analysis of weight gain rate,specific growth rate,and feed conversion ratio,the recommended dietary vitamin A requirement for juvenile Procambarus clarkii is 37976-43443 IU/kg.