| Shrimp extract(ShE)is rich in amino acids,small peptides,nucleotides and astaxanthin.It's a new type of high protein aquatic animal additive.ShE could replace fishmeal as a source of protein,improve the palatability of aquatic feed,and stimulate the appetite of aquatic animals.In order to study the effects of ShE on the growth,muscle nutrition and immunity of juvenile red tilapia,270 tails of healthy red t ilapia with an average body weight of 12.02 ± 0.02 g were selected for the experiment and fed with diet ShE.The experiment fish were randomly divided into six groups with triplicate,and a 62-day experiment was conducted.According to the concentration of ShE and and whether containing fish meal is divided into following groups: 0%(D1),0.5%(D2),1%(D3),2%(D4),3%(D5)and fish meal group(D6).D1 group was negative control group,fed basic diet without fish meal;D2,D3,D4 and D5 groups were experimental group,fed with different levels of ShE diet;D6 group was positive control group,fed basic diet with fish meal.The effects of ShE on juvenile red tilapia were discussed from different angles.The main results are as follows:1.Effect of dietary ShE levels on the growth,muscle nutrition and related gene expression of juvenile red tilapiaAt the end of the experiment,tilapia in the 3% ShE diet group and the FM diet group had significantly higher final body weight(FBW),weight gain rate(WG),specific growth rate(SGR),and food intake(FI)than other diet groups(P<0.05).ShE diet group and FM diet group had no significant effect on moisture and crude protein in red tilapia muscle(P>0.05),but ShE diet group can significantly increase muscle crude fat content(P<0.05),and 1% The crude fat content of the ShE diet group was the highest;the ash content of the 0%,0.5% and 2% ShE diet group was significantly lower(P<0.05).Although there was a decrease in the content of essential amino acids and non-essential amino acids in each experimental group,there was no significant difference compared with the control group(P>0.05).The total muscle saturated fatty acid(SFA)of the ShE diet group was lower than that of the FM diet group(P<0.05).Meanwhile the contents of erucic acid(C22:1),eicosapentaenoic acid(C20:5 n-3;EPA),docosapentanoic acid(C22:5 n-3;DPA)and docosahexaenoic acid(C22:6 n-3;DHA)in ShE diet groups were also lower than that in FM diet group(P<0.05).The expression level of lpl gene in the liver of the experimental group was significantly higher than that of the control group(P<0.05).The expression levels of liver mdh gene in the 0.5%,2% and 3% ShE diet groups of the red tilapia group were significantly higher than those of the other groups(P<0.05).2.Effect of dietary ShE levels on the biochemical parameters,immunity and related genes of juvenile red tilapiaShE could change the activities of alanine aminotransferase(ALT),aspartate aminotransferase(AST)and alkaline phosphatase(AKP)in the liver of red tilapia,and had the greatest influence on ALT activity.The activity of ALT in 0.5% ShE diet group was significantly higher than that in fish meal group(P<0.05),and activity of aspartate aminotransferase(AST)in 0% and 1% ShE diet group were significantly lower than that in 0.5%,2% and 3% ShE ShE diet group.The expression of hsp70 gene in ShE diet group was significantly higher than that in control group(P<0.05);the 1% ShE diet group had the highest gsh-px1 gene expression(P<0.05);the expression of c-type lysozyme gene in 0.5%,1% and 2% ShE diet group were significantly higher than that in control group(P<0.05);and the expression of hepcidin gene was the highest in 2% and 3% ShE diet group(P<0.05).3.Effect of dietary ShE levels on the expression of color genes in juvenile red tilapiaMc1r,tyr and scl7a11 genes expression level were the highest in the FM diet group,and the asip gene had the highest expression level in the 0.5% ShE diet group,but there was no significant difference between the groups(P>0.05).Also there was no significant increase or decrease in the body color related genes of each group with the addition of ShE in the diet. |
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