Effects Of Replacement Of Fish Meal And Fish Oil By Nannochloropsis Sp.meal On Growth,Tissue Proximate Composition And Biochemical Indices Of Juvenile Turbot(Scophthalmus Maximus L.)

A 70-day trial was conducted to investigate the effects of replacement of dietary fish meal by Nannochloropsis sp.meal on growth performance,body composition and serum biochemical indices of juvenile turbot Scophthalmus maximus L.with initial weight of（24.60±0.02g）.Five isonitrogenous and isoenergetic diets(T₀,T_3.88,T_7.66,T_11.641.64 and T_15.52)were formulated with 0%,3.88%,7.66%,11.64%and 15.52%total fish meal replaced by Nannochloropsis sp.meal,respectively.Each diet was randomly fed to three replicates with 40 fish per replicate.Results showed that:1)There were no significant differences（P>0.05）of weight growth rate,protein efficiency ratio,feed coefficient ratio,daily feeding intake,condition factor and the survival rate among groups;2)With the increasing of Nannochloropsis sp.meal,crude lipid contents of whole body and muscle was significantly decreased（P<0.05）,however the crude protein,crude ash and moisture had no significantly differences（P>0.05）;3)The lysozyme,complement protein C₃,complement protein C₄ and acid phosphatase activities showed a trend of rising first and then declining,which reached the peak at the T_7.76,T_7.76,T_11.64 and T_7.76 group respectively and significantly higher than the T₀ group（P<0.05）.The alkaline phosphatase activity of T_15.52 group was significantly lower than other groups and there were no significantly differences among other groups（P>0.05）;4)The total superoxide dismutase,total antioxidant capacity and glutathione peroxidase activities of serum of the algae meal groups increased firstly and then decreased,reached the peakat the T_7.76 group which was significantly higher than the T₀ group（P<0.05）;5)The triglyceride content of serum of the T_7.76.76 group was significantly lower than other groups（P<0.05）,but there were no significantly differences among other groups（P>0.05）;The total cholesterol content of the algae meal groups was significantly lower than the T₀ group（P<0.05）,but there were no significantly differences among the algae meal groups;6)The asparate aminotransferase activity of serum of the algae meal groups showed a trend from declining to rising,which reached the lowest level at the T_11.64 group and were significantly lower than the T₀ group（P<0.05）;The alanine aminotransferase activity of the algae meal groups was significantly lower than the T₀ group（P<0.05）.In conclusion,under the present experimental condition,Nannochloropsis sp.meal could replace 15.52%fish meal,which had no effects on the growth performance,and replacing 7.76%fish meal can significantly improve the nonspecific immunity and reduce the blood lipid level of juvenile turbot.A feeding trial was conducted to study the effects of dietary fish oil replacement by Nannochloropsis sp.meal on serum biochemical indices,tissue proximate composition and body fatty acid composition in turbot.Five isonitrogenous and isoenergetic diets(T₀,T₈,T₁₆,T₂₄,T₃₂)were formulated with 0%,8%,16%,24%and 32%total fish oil replaced by Nannochloropsis sp.meal.A total of 375 juvenile turbots（82.64±0.32）g were randomly divided into 5 groups,each with 3 replicates.Each replicate included 25fish.The feeding trial with the period of 37 days was carried out.Results showed that:1)There were no significant differences on specific growth rate,protein efficiency ratio,daily feeding intake and feed coefficient ratio among groups（P>0.05）;2)Crude protein content of the whole fish presented an increasing trend,the experimental groups were significantly higher than the control group（P<0.05）.Crude lipid content of the whole fish presented an declining trend,The control group was significantly higher than the experimental groups（P<0.05）.However,crude ash and moisture had no significantly differences（P>0.05）;3)Crude protein,crude lipid,crude ash and moisture content of muscle showed the same trend as those of whole fish,respectively;4)The percentage of arachidonic acid in muscle and liver increased with the increasing dietary Nannochloropsis sp.meal content,and that of T₂₄4 and T₃₂2 groups were significantly higher than the control group（P<0.05）.However,the n-3/n-6 HUFA content presented an opposite tendency,and that of T₂₄ and T₃₂ groups were significantly lower than the control group（P<0.05）;5)The total superoxide dismutase and total antioxidant capacity of serum increased with the increasing dietary Nannochloropsis sp.meal up to T₁₆ diet which was significantly higher than the control group（P<0.05）,and there after declined.The lysozyme activity of serum increased firstly and then decreased,and that of T₁₆6 and T₂₄4 group were significantly higher than the control group（P<0.05）.The malondialdehyde content of serum showed a first declining then rising trend,reached the lowest level at T₁₆6 group which was significantly lower than the control group（P<0.05）;6)The low density lipoprotein cholesterol of serum showed a descending tendency and that of the control group was significantly higher than the experimental groups（P<0.05）.The high density lipoprotein cholesterol of serum showed a first rising then descending trend among groups（P>0.05）,but there were no significantly differences among groups（P>0.05）.The triglyceride content and the total cholesterol content of serum showed a descending tendency,and that of T₂₄ and T₃₂ groups were significantly lower than the control group（P<0.05）.In conclusion,under the present experimental condition,Nannochloropsis sp.meal could replace fish meal of the juvenile turbot diet,which had no effects on the growth performance and enhanced protein content in whole fish and muscle.The non-specific immune response and antioxidant capacity of the experimental groups were improved at the replacement levels of 16%-24%.In addition,the replacement kept the content of high unsaturated fatty acids in juvenile turbot（Scophthalmus maximus L.）,maintaining its nutritional value.