Study On Dietary Optimum Leucine Requirement And Interactive Effect Of Dietary Isoleucine And Leucine On Growth And Physiological Metabolism Of Juvenile Sea Cucumber Apostichopus Japonicus Selenka

A 60-d feeding trial was conducted to determine the dietary leucine requirement of juvenile(16.40±0.14g)sea cucumber Apostichopus japonicus.We formulated six experimental diets that the graded leucine levels 1.29%(D1,control group),1.63%(D2),1.98%(D3),2.22%(D4),2.58%(D5)and 2.97%(D6)dry diets.There were no differences on survival rate among all groups(96.00%～98.67%).The WGR and the SGR increased with increasing leucine content until reaching peak levels at 1.98% dietary leucine,but decreased thereafter.The WGR and SGR of D3,D4 and D5 groups were significantly higher than D1 group.The crude lipid contents of body wall was increased when dietary leucine content increased from 1.29% to 1.98% but decreased when the dietary leucine content exceeded 1.98%,D3 group was significantly higher than other groups,but there were no significant effects on moisture,crude protein and crude ash contents.Both methionine and leucine content of body wall were significantly increased by dietary leucine,but there were no significant effects on total amino acids(TAA).Both lipase and protease activities of intestinal were increased with increasing levels of leucine up to 1.98% diet and then decreased.The lipase of D3 group was significantly higher than other groups.All of alanine aminotransferase(ALT),asparate aminotransferase(AST)and total antioxidant capacity(T-AOC)activities of intestinal were increased when dietary leucine content increased from1.29% to 1.98%.There were no significant effects on AST activity when the dietary leucine content exceeded 1.98%,but the ALT and T-AOC activities were decreased.The catalase(CAT)and superoxide dismutase(SOD)activities reached maximum value when the dietary leucine content was 2.22%.The malondialdehyde(MDA)content was decreased when dietary leucine content increased from 1.29% to 1.98% but increased when the dietary leucine content exceeded 2.22%,the MDA contents of D3 and D4 groups were significantly lower than other groups.The results showed that the optimum dietary leucine of sea cucumber with 16.40 g was 2.11% diet(10.37% dietary protein).A 60-d feeding trial was conducted to determine the interactive effects of Ile and Leu on growth physiological metabolism of juvenile sea cucumber Apostichopus japonicus with initial body weight(16.40±0.14)g.Nine experimental diets containing 3 Ile levels combined with 3 Leu levels as a 3×3 experimental design:LI-LL(0.52%Ile,1.29%Leu),LI-ML(0.59%,1.98%),LI-HL(0.56%,2.58%),MI-LL(0.91%,1.33%),MI-ML(0.97%,1.95%,control group),MI-HL(0.93%,2.68%),HI-LL(1.30%,1.39%),HI-ML(1.32%,1.99%)and HI-HL(1.31%,2.72%).The results showed that: The interactive effect of dietary Ile and Leu can significantly affect the WGR and SGR of sea cucumber.The dietary Ile can significantly affect the WGR and SGR,and the dietary Leu can extremely significant affect the WGR and SGR.The WGR and SGR of MI-LL and HI-LL groups were significantly higher than other groups.The WGR reached maximum value of 111.39% in the HI-LL group.The interactive effects of dietary Ile and Leu were found on crude lipid contents of body wall.The crude lipid contents of HI-LL and LI-ML groups were significantly higher than other groups.But there were no interactive effects on moisture,crude protein and crude ash contents.The interactive effect of dietary Ile and Leu can significantly affect the amylase,protease and lipase activities of intestinal.The amylase activities of HI-LL group reached maximum value and significantly higher than middle Ile groups.The protease activities of LI-ML,MI-HL and HI-LL were significantly higher than other groups.The lipase activities of high Ile groups were significantly higher than low Ile groups.All of ALT,AST,ACP and AKP activities of intestinal were significantly effects by interactive of dietary Ile and Leu.The ACP and AKP activities of HI-LL group reached maximum value and significantly higher than control group.The interactive effect of dietary Ile and Leu can significantly affect the T-AOC,SOD,CAT activities and MDA content of intestinal.The T-AOC and CAT activities of HI-LL group reached minimum value and significantly lower than other groups.This study suggested that the interactive effect of dietary Ile and Leu can significantly affect the growth,nutrient composition of body wall,digestive enzyme activities and antioxidant capacity of juvenile sea cucumber.With growth,nutrient composition of body wall and digestive enzyme activities as evaluation indicator,the best performance of sea cucumber would be HI-LL diets,but this group have the worst performance on antioxidant capacity.With growth and performance on antioxidant capacity as evaluation indicator,that the optimum dietary Ile and Leu of sea cucumber with body weight 16.40 g were 0.91%and 1.33%(middle Ile,low Leu).