Dietary Valine Requirement Of Juvenile Nile Tilapia (Orechromis Niloticus)

In this study,8-week feeding trials were conducted to examine the effects of dietary valine on feeding,growth performance,body composition,hematology and immune response in Nile tilapia in indoor water system.Six isonitrogenous and isoenergetic semi-purified experimental diets,using casein and gelatin as intact protein sources supplemented with a crystalline amino acid mixture and soybean oil as the lipid sources,were formulated to contain graded leves of valine,replaced by the same proportions of glycine.The experimental results are presented as follows:Effects of dietary valine on growth performance,body composition,hematology and essential acid(EAA)on muscle of juvenile Nile tilapia.Fish of similar sizes(intial weight being 6.50±0.05g)were randomly chosen and sorted into eighteen cages with 20 fish per cage.Each experimental diet(the final levels of valine were 0.493%?0.720%?0.960%?1.317%?1.489%?1.781%)was randomly assigned to triplicate buckets in a completely randomized design.The feeding trial lasted for 8 weeks.Results showed that final body weight(FBW),specific growth rate(SGR),protein efficiency ratio(PER)significantly increased with increasing dietary valine levels from 4.93 g/kg to 13.17 g/kg and thereafter decline slowly,while feed conversion ratio(FCR)showed an adverse trend.Compared to fish fed control diet(0.493%valine diet),FBW,WGR and SGR were significantly improved when fish fed 1.317%?1.489%and 1.781%valine diet(P<0.05).When the valine at the 1.489%level in the experimental group,food intake and fatness in juvenile nile tilapia was significantly higher than the other groups(P<0.05),while the liver body weight ratio(HSI)was significantly lower than the other groups.Valine levels have a significant impact on the Nile tilapia protein efficiency(PER)and protein deposition rate(PPV).First rise,after that showing a downward trend in all.No significant differerces were observed in moisture,crude fat,crude protein and crude ash content of fish fed different dietary valine levels(P>0.05).No significant differerces were observed in muscle valine,histidine,isoleucine,leucine,lysine,arginine,phenylalanine,threonine,tyrosine and alanine content of fish fed different dietary valine levels(P>0.05).No significant differerces(P>0.05)were in essential amino acids except methionine muscle outside while fish fed different dietary valine levels.With increasing levels of dietary valine,white blood cell(WBC)firstly increased the total decline,erythrocytes(RBC)total hemoglobin(HGB)content,hematocrit(HCT)showed no significant difference(P>0.05).With the improvement of the level of valine,glutamate dehydrogenase(GDH)in 0.960%level was significantly higher than other groups of glutamate dehydrogenase(GDH)activity(P<0.05).Serum catalase at 1.317%level set slightly higher than the other groups of serum alanine aminotransferase(ALT),aspartate aminotransferase(AST)activity first and then reduce elevated trend(P<0.05),Triglyceride(TG)at 1.317%and 1.781%of valine in the experimental group was significantly higher than 0.493%,0.720%of valine in the experimental group(P<0.05),blood urea nitrogen(UREA)showed a downward trend,urea nitrogen(UREA)at 1.317%,1.489%,1.781%in the experimental group of valine were significantly lower than 0.493%,0.720%of valine in the experimental group(P<0.05).Valine levels on juvenile Nile tilapia's liver of lysozyme(LZM)activity has a significant influence(P<0.05),while liver superoxide dismutase(SOD)had no significant effect(P>0.05).Liver lysozyme(LZM)activity at level of 1.781%valine was significantly higher than other groups of valine levels(P<0.05),Catalase(CAT)activity with increasing levels of valine feed first and then increased and then decreased,at 1.489%of valine,Catalase(CAT)was significantly lower than 1.317%of valine level group(P<0.05).No significant differerces were observed in juvenile Nile tilapia's liver of superoxide dismutase activity(P>0.05).The optimum valine requirements were estimated in 1.39%feed content(g/100g)and 1.41%(g/100g),it is based on WGR and PPV in different dietary valine levels,respectively,using quadratic regression analysis.