Studies On The Lysine Requirements Of Juvenile Yellowcheek Carp, Elopichthys Bambusa

The purpose of this study was to investigate the ability of juvenile yellowcheek carp to use crystalline amino acids under the experimental environment, and the effects of dietary lysine level on growth performance, feed utilization, body composition, blood parameters and digestion of juvenile yellowcheek carp. And then to determine the lysine requirements of juvenile yellowcheek carp. Seven isonitrogenous (Crude protein46%) and isolipidic (Crude lipid9%) diets were formulated. The diet which only had two intact proteins (fish meal and casein) as protein source was the control diet. L-amino acids HCl was supplemented to the other six diets to achieve lysine levels at1.96%,2.45%,2.95%,3.46%,3.94%and4.45%. The other amino acids achieved the same pattern of yellowcheek carp muscle. Each diet was randomly assigned to triplicate groups of18fish (initial mean weight:2.36±0.08g). The experiment continued for eight weeks.The results shown that the WGR of control diet group was significantly higher then the experimental groups(P<0.05). The SGR of control diet group was higher then the experimental groups, and had no significant difference with D4and D5group (P>0.05). FCR of control diet group had no significantly with D2, D3, D4and D5group (P>0.05). PER of control diet group had no significantly with experimental groups (P>0.05). PPV was only significantly higher than the D6group (P<0.05), and had no significant differences (P>0.05) with the other groups. Only whole fish, muscle and liver of crude fat of control diet group showed significant differences (P<0.05) with the experimental groups. AST and ALT activity of control diet group were lower compared with the experimental groups.WGR, SGR, Apparent digestibility coefficients of dry matter and protein, liver lipase relative activities and protein, Cholesterol, AKP activities in serum of juvenile yellowcheek carp first increased and then decreased with increasing dietary lysine level. The FCR shown the trend first increased and then decreased with the dietary lysine level. Fitted by regression analysis, relationship between SGR and dietary lysine level for juvenile yellowcheek carp based on quadratic regression analysis was:Y=-0.40X2+2.70X-1.49, correlation coefficient:R2=0.81, the optimum lysine level was of3.41%dry weight,7.41%in protein. Relationship between SGR and dietary lysine level for juvenile yellowcheek carp based on broken-line analysis was:Y=3.07-0.80(2.90-X), when X>2.90,(2.90-X)=0, correlation coefficient:R2=0.81, the optimum lysine level was of2.90%dry weight,6.30%in protein.The results Suggested that CAA could be well used in the feed by juvenile yellowcheek carp. The suitable level of lysine was between2.90%to3.10%in dry diet, and6.30%to6.74%in protein. The most appropriate level in the diet was2.90%in dry diet (6.30%in protein).