| In this paper,the effects of methionine,valine and isoleucine on the growth performance,body composition,intestinal digestive enzyme activity and antioxidant enzyme activity of juvenile sea cucumber(Apostichopus japonicus selenka)were studied.With the weight gain rate as the evaluation index,through the regression analysis,to obtain the optimum requirements of the three kinds of amino acids of juvenile sea cucumber(Apostichopus japonicus selenka).The results are as follows:An 8-week feeding experiment was conducted to determine the dietary methionine requirement of juvenile sea cucumber Apostichopus japonicus(selenka)with initial body weight(12.14±0.14)g.Six experimental diets were formulated with the graded methionine levels(0?0.40%?0.80%?1.20%?1.60% and 2.00% dry diets,respectively).The six trial diets were determined to contain methionine of(0.18%,D1;0.37%,D2;0.57%,D3;0.78%,D4;0.96%,D5;1.10%,D6 dry diet),respectively.Each diet was randomly assigned to triplicate groups of 30 sea cucumbers in a recirculated system.The results showed that there was no significant difference in the survival rate(SR)among dietary treatments(P>0.05).Weight growth rate(WGR)and the specific growth rate(SGR)significantly increased initially and then decreased as dietary methionine level increased and those of D3 were significantly higher than other groups.Dietary methionine had no significant effects on ratio of intestine weight to body wall weight(IBR)and ratio of intestine length to body length(IBL)of sea cucumber.Crude protein and crude lipid of body wall increased initially then decreased.Dietary methionine significantly increased Met,Cys,Asp,essential amino acids(EAA)and total amino acids(TAA)contents of body wall.Total antioxidant capacity(T-AOC)and total superoxide dismutase(T-SOD)of intestine increased with the increasing of dietary methionine levels and those of D1 were significantly lower than other groups(P<0.05).Malondialdehyde(MDA)content decreased withincreasing levels of methionine,and that of D1 was significantly higher than other groups.Trypsin and lipase increased initially and then decreased,however,there was no significantly effect on amylase of dietary methionine(P>0.05).In conclusion,appropriate dietary methionine improved significantly growth performance and immune response and modified chemical composition and amino acid contents of sea cucumbers.With WGR as evaluation indicator,regression analysis of broken-line model showed that the optimum dietary methionine of sea cucumber with body weight 12.14 g was 0.58%(2.77% diet protein).An 8-week feeding trial was conducted to determine the dietary valine requirement of juvenile sea cucumber Apostichopus japonicus(selenka)with initial body weight(9.20±0.12)g.Six experimental diets were formulated with the graded valine levels(0?0.80%?1.60%?2.40%?3.20% and 4.00% dry diets,respectively).The six trial diets were determined to contain valine of(0.61%,D1;1.14%,D2;1.46%,D3;1.73%,D4;2.17%,D5 and 2.64%,D6 dry diet),respectively.The results showed that:(1)No significant differences in the survival rate(SR)were found among dietary treatments(P > 0.05);the weight growth rate(WGR)and the specific growth rate(SGR)offered upgrade with increasing levels of valine up to 1.73% diet(P<0.05),and thereafter,declined.(2)There were no significant effects on ratio of intestine weight to body wall weight(IBR)and ratio of intestine length to body length(IBL)of sea cucumber.(3)Crude protein and crude lipid of body wall increased initially then decreased,and crude protein of diet D4 was significantly higher than those of any other groups(P < 0.05).Dietary valine significantly increased His,Val,essential amino acids(EAA)and total amino acids(TAA)contents of body wall,but decreased Leu,Ile and Tyr contents.(4)Total superoxide dismutase(T-SOD)and total antioxidant capacity(T-AOC)increased with the increasing of dietary valine levels and those of D1 were significantly lower than other groups(P < 0.05).Malondialdehyde(MDA)content decreased with increasing levels of valine up to1.73% diet and then increased,and MDA of D4 was significantly lower than those of other groups.(5)Protease and lipase increased initially and then decreased,and protease of D3 was significantly higher than those of other groups(P < 0.05),however,there was no significantly effect on amylase of dietary valine(P>0.05).In conclusion,appropriate dietary valine improved significantly growth performance and immune response and modified chemical composition and amino acid contents of sea cucumbers.With WGR as evaluation indicator,regression analysis of broken-linemodel showed that the optimum dietary valine of sea cucumber with body weight9.20 g was 1.79%(9.18% diet protein).An 8-week feeding trial was conducted to determine the dietary isoleucine requirement of juvenile sea cucumber Apostichopus japonicus(selenka)with initial body weight(9.20±0.09)g.Six experimental diets were formulated with the graded valine levels(0?0.4%?0.8%?1.2%?1.6% and 2.0% dry diets,respectively).The six trial diets were determined to contain valine of(0.52%,D1;0.71%,D2;0.95%,D3;1.20%,D4;1.43%,D5 and 1.57%,D6 dry diet),respectively.The results showed that:(1)No significant differences in the survival rate(SR)were found among dietary treatments(P > 0.05);the weight growth rate(WGR)and the specific growth rate(SGR)offered upgrade with increasing levels of valine initially,and thereafter,declined,and those of D1 were significantly lower than other groups.(2)There were no significant effects on ratio of intestine weight to body wall weight(IBR)and ratio of intestine length to body length(IBL)of sea cucumber.(3)Crude protein and crude lipid of body wall increased initially then decreased.Dietary isoleucine significantly increased His,Ile,Lys,Asp,Tyr,essential amino acids(EAA)and total amino acids(TAA)contents of body wall,but declined Leu and Val contents.(4)Total antioxidant capacity(T-AOC)and total superoxide dismutase(T-SOD)went up with the increasing of dietary valine levels and those of D1 were significantly lower than other groups(P < 0.05).Malondialdehyde(MDA)content initially decreased with increasing levels of isoleucine and then increased,and MDA of D1 was significantly higher than those of other groups.(5)Protease and lipase increased initially and then decreased,and protease of D3 was significantly higher than those of other groups(P<0.05),however,there was no significantly effect on amylase of dietary valine(P>0.05).In conclusion,appropriate dietary isoleucine improved significantly growth performance and immune response and modified chemical composition and amino acid contents of sea cucumbers.With WGR as evaluation indicator,regression analysis of broken-line model showed that the optimum dietary valine of sea cucumber with body weight 9.20 g was 0.98%(5.06% diet protein). |
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