Research On The Effects Of Replacement Of Fish Oil By Two Kinds Of Microalgae Meals On Growth,Tissue Proximate Composition,Biochemical And Immunity Of Juvenile Starry Flounder,Platichthys Stellatus

In this paper,a experience was conducted to investigate the effect of fish oil substitution with Schizochytrium meal,Nannochloropsis meal and the mixture of these two algae meals on growth,tissue proximate composition,biochemical and immunity of juvenile starry flounder Platichthys stellatus(initial weight 7.35± 0.03 g).Specific results are as follows:PART 1:A 90-days experience was conducted to investigate the effect of fish oil substitution with microalgae meals on growth performance,tissue proximate composition and biochemical indices of juvenile starry flounder Platichthys stellatus(initial weight 7.35± 0.03 g).Four groups of isonitrogenous and isolipidic diets formulated with different primary lipid sources: fish oil(FO),Schizochytrium meal(SO),Nannochloropsis meal(NO)and the mixture of these two algae meals(MO),with the insufficient part filled with corn oil.Results showed that: 1)There was no significant difference of feed intake rate(FIR),condition factor(CF)and hepatosomatic index(HIS)between each group(P>0.05),and the growth performance was not significantly changed between FO and SO,whereas specific growth rate(SGR),protein efficiency ratio(PER)and viscerosomatic index(VSI)of NO and MO were significantly lower than FO(P<0.05),and feed efficiency(FE)of MO and NO is just the opposite.2)The substitution of fish oil with microalgae meals had no significant effect on the body crude ash,as well as the muscle crude protein and crude lipid(P>0.05).The body crude protein content of MO was the significantly highest(P<0.05),while body crude lipid content of FO and MO were significantly higher than other groups(P<0.05).The muscle ash content of FO was significantly lower than others(P<0.05).3)Fatty acid composition of muscle and liver were directly influenced by dietary fatty acid composition(P<0.05).The percentage of C16:0 and DHA of muscle was positively correlated with that of the diets(r=0.973,0.967,P<0.05),while the percentage of C14:0 and C16:1n-7 was extremely significantly positive with that of the diets(r=1.00,0.996,P<0.01).The percentage of C18:2n-6,n-6 PUFA and DHA / EPA ratio of liver was also positively correlated with that of the diets(r=0.983,0.976,0.977,P<0.05),while C16:1n-7 showed an extremely significantly positive correlation(r=0.992,P<0.01).Compared with FO,levels of serum alanine aminotransferase(ALT),triglyceride(TG),cholesterol(CHO)and alkaline phosphatase(ALP)of NO and MO were significantly decreased(P<0.05).Beside,levels of serum aspartate aminotransferase(AST)and glucose(GLU)of NO was significantly lower than that of other groups(P<0.05).In short,under the present experimental conditions,there were no negative effects on growth and physiology when fish oil was replaced by Schizochytrium meal,and that even can improve the nutritional value of Platichthys stellatus in a certain extent.PART 2:To study the effects of fish oil substitution with microalgae meals on lipid metabolic enzyme,antioxidant capacity and non-specific immunity of juvenile starry flounder Platichthys stellatus,a 90-days culture experiment with initial body weight of 7.35± 0.03 g was carried out.Four groups of isonitrogenous and isolipidic diets were formulated with different primary lipid sources: fish oil,Schizochytrium meal,Nannochloropsis meal and the mixture of these two algae meals,with the insufficient part filled with corn oil,and were named FO,SO,NO,MO.The results showed that: 1)Compared with FO,the activity of hepatic lipase(HL),lipoprotein lipase(LPL)and total lipase(TLP)were significantly increased in all the substitution groups except the HL of MO(P<0.05).The activity of glucose-6-phosphatedehy drogenase(G6PD)and fatty acid synthetase(FAS)in the substitution groups were significantly lower than those in the control group(P<0.05).The activity of acyl-Coenzyme aoxidase(ACO)in MO was significantly higher than FO and NO(P<0.05),but there were no significant differences between SO and other experiment groups(P>0.05).2)Replacement fish oil with algae meals had no significant effect on the serum malondialdehyde(MDA)(P > 0.05),but significant increased the serum total anti-oxidation capability(T-AOC)of the substitution groups(P<0.05).Compared with FO,the liver T-AOC of NO and MO significantly increased(P<0.05).The liver MDA of SO were significantly higher than other groups(P<0.05).3)Replacement fish oil with algae meals had significant effects on the non-specific immunity of juvenile starry flounder(P<0.05),besides the acid phosphatase.Compared with the control group,the complement 3(C3)activity of NO decreased significantly(P<0.05),however SO and MO showed the opposite trend(P<0.05).The activity of Lysozyme(LZM)in SO was much higher than that in the other three groups,significantly(P<0.05).After 7 days of attack,the survival rate of SO was significantly higher than the other three experimental groups(P<0.05).This study suggested,under the experimental condition,algae meals replaced fish oil of the juvenile starry flounder feed could improve the ability of body lipid metabolism to a certain extent,and no negative effect was found on the liver function,increasing the antioxidant capacity and non-specific immunity as well.