Effects Of Lipid Sources And Protein Sources In Dietary On Growth,Physiology And Biochemistry Of Trachinotus Ovatus

Golden pompano(Trachinotus ovatus)is a carnivorous fish,which mainly preys on zooplankton and small crustaceans,shellfish and fish.This fish,which is popular among consumers,is considered a high quality marine food fish based on its white and delicious meat and fast growth.Lipids and proteins are two major nutrients in organisms and play an important role in promoting growth,development,immunity and health.Fish oil(FO)and fish meal(FM)have always been the most used fat source and protein source in traditional aquafeeds.However,due to the rising demands and increasing prices of FO and FM,exploring suitable lipid sources and protein sources has become an urgent problem for the aquatic industry.In the present study,we were dedicated to elucidating the effects of lipid sources and protein sources in dietary on growth,physiology and biochemistry of Trachinotus ovatus.The results might be useful to explore a potential lipid sources and protein sources.In addition,this study might provide a theoretical basis for a more efficient and healthy feeds for golden pompano.1.Effects of different lipid sources on growth performance,physiology and biochemistry in Trachinotus ovatusThe experimental fish were selected 640 golden pompanos,which mean body weight was 82.85±2.36 g.After one week of domestication,golden pompanos were randomly sorted into 32 cages.There were 8 groups in the experiment,4 replicates in each group,and 20 fish per replicate.Eight diets that contained different lipid sources were formulated,including fish oil(FO),krill oil(KO),soybean oil(SO),corn oil(CO),1:1 FO-SO,1:1 FO-CO,1:1 KO-SO and 1:1 KO-CO.The breeding cycle was 8 weeks.(1)Effects of different lipid sources on growth performance,muscle quality and serum biochemistey in Trachinotus ovatusThe results showed that the specific growth rates in the SO,CO,1:1 FO-SO and 1:1 KO-SO groups were significantly lower than that in the FO group(P<0.05),but KO,1:1FO-CO,1:1 KO-CO groups had no significant difference with the FO groups(P>0.05).There was no significant difference in the feed conversion ratio and hepatosomatic index between other seven groups and FO group(P>0.05).But the highest feed conversion ratio was found in the SO group and the highest hepatosomatic index was found in the CO group.The lowest protein content and the highest lipid content were found in the FO group.The composition of muscle fatty acids was directly affected by the fatty acid composition of the dietary.The content of SFAs in other seven groups was significantly lower than that in the FO group(P<0.05).The levels of n-3 PUFA,EPA and DHA were significantly higher in the fish fed KO group than FO group(P<0.05).And the level of n-6 PUFA in other seven groups was significantly higher than that in the FO group(P<0.05).The n-3/n-6 level of other seven grous in the muscle was significantly lower than that in the FO group except the KO group(P<0.05).Compared with FO group,the fish muscle in KO group had a betteer muscle quality.In serum biochemistry,cholesterol content was significantly higher in the fish fed 1:1 KO-CO group than FO group(P<0.05),and triglyceride content was highest in CO group and significantly higher than FO group(P<0.05).The malondialdehyde content of the other groups was significantly lower than that of the FO group except the 1:1 KO-CO group(P<0.05),and the lowest malondialdehyde content was found in the KO group.The activity of alanine aminotransferase was significantly lower in the fish fed 1:1 FO-CO group than FO group(P<0.05),and the highest alanine aminotransferase activity was found in the FO group.(2)Effects of different lipid sources on hepatic lipid metabolism-related gene expression and intestinal microbiota of Trachinotus ovatusDifferent lipid sources had significant effects on lipid metabolism-related gene expression of Trachinotus ovatus.The relative expression of fas in the liver of the four groups of mixed oils was significantly lower than that in the FO group(P<0.05),and the highest relative expression of fas was found in the FO group.The relative expression of acc? in the 1:1 KO-SO group was significantly lower than that in FO group(P<0.05),and the highest expression of acc? was also detected in FO group.The lowest relative expression levels of hsl1,ppar? and ppar? were detected in the FO group.The relative expression of atgl in the SO and CO groups was significantly higher than that in FO group(P<0.05).No significant difference was found between the other seven groups and FO group in Alpha diversity(P>0.05).Bacteroidetes,Firmicutes,Proteobacteria and Tenericutes were mainly detected,and Proteobacteria were detected as the predominant phyla in the intestine of golden pompano.Due to the greater influence of lipd sources,intestinal microbiota in each group differed greatly in species evolution and species composition.In view of the effects of different lipid sources on the growth,muscle quality,serum biochemistry,intestinal microbiota and hepatic lipid metabolism-related gene expression,KO could replace fish oil in golden pompano.The four groups of mixed oils promote growth,improve immune status and intestinal health in a certain extent.2.Substitution of fish meal by fermented soybean meal affects the growth performance,physiology and biochemistry in Trachinotus ovatusThe experimental fish were selected 750 golden pompanos,which mean body weight was 42.64±4.68 g.After one week of domestication,golden pompanos were randomly sorted into 15 cages.There were 5 groups in the experiment,3 replicates in each group,and 50 fish per replicate.Five diets were formulated,adding 0(FM),25%(FSM25),50%(FSM50),75%(FSM75),and 100%(FSM100)fermented soybean meal to replace fish meal.In order to balance the effects of limiting amino acids,adding 0%,0.10%,0.22%,0.35% and 0.45% lysine,and 0%,0.14%,0.27%,0.41% and 0.54% methionine,respectively.The breeding cycle was 8 weeks.(1)Effects of substitution of fish meal by fermented soybean meal on the growth performance,muscle composition and serum biochemistry in Trachinotus ovatusThe results showed that FSM25 and FSM50 groups had no significant difference with FM group in weight gain rate,specific growth rate,feed intake and condition factor(P>0.05),and the feed conversion ratio of FSM100 group was significantly higher than that in FM group(P<0.05).According to the regression curve,the best substitution level is 17.5%.Substitution of fish meal by fermented soybean had no significant effect on the crude fat,crude protein,ash and amino acid content of the muscle.The activity of aspartate aminotransferase in FSM75 and FSM100 groups were significantly higher than those in FM group(P<0.05).The activities of alanine-transferase and superoxide dismutase in FSM100 group were the highest and significantly higher than that in FM group(P<0.05).(2)Effects of substitution of fish meal by fermented soybean meal on the liver tissue morphology,growth-related gene expression in Trachinotus ovatusThe liver tissue morphology of the FM group was normal.The liver cell size was normal and clearly visible,and the cell boundaries were more obvious.Compared with the FO group,with the increasing replacement ratio,the number of round vacuoles in the hepatocytes increased,and the nucleus was squeezed to one side,the liver damage aggravated.The results of qRT-PCR showed that the expression of growth-related genes were consistent with the growth results.The relative expression levels of IGF-1,IGF-2 and GH in FSM75 and FSM100 groups were significantly lower than those in FM group(P<0.05),and no significant difference was found between FSM25,FSM50 and FM groups.Compared with the FM group,the fermented soybean meal replaced fish meal amount of no more than 50% did not adversely affect the growth of golden pompano.If exceeding this range,it will inhibit growth performance.In view of the effects of fish meal replaced by fermented soybean meal on the growth performance,muscle nutrient composition,serum biochemistry,liver tissue morphology and growth-related gene expression,the ratio of fermented soybean meal to fish meal is not more than 50%.According to the regression curve,the best substitution level is 17.5%.