Effects Of Dietary Fish Oil Replaced With Black Soldier Fly (Hermetia Illucens) Larvae Oil On The Growth And Lipid Metabolism Of Yellow Catfish (Peltobagrus Fulvidraco)

This study was conducted to assess effects of dietary fish oil replaced with black soldier fly(hermetia illucens)larvae oil on growth performance,body composition,apparent digestibility of nutrients,serum biochemical indicators,antioxidant index,immune index,fatty acid composition,liver lipid metabolism gene expression and liver tissue structure of yellow catfish(peltobagrus fulvidraco).1.Effects of dietary fish oil replaced with black soldier fly larvae oil on growth performance,immune indices,antioxidant indices and liver tissue structure of yellow catfish.A 56-d feeding experiment was conducted to investigate the effects of dietary fish oil(FO)replacement by black soldier fly larvae oil(BSFO)on growth,body composition and fatty acid composition of juvenile yellow catfish.Four onitrogenous and isolipidic practical diets were formulated with BSFO replacing 0(T0),20%(T20),40%(T40),60%(T60),80%(T80)and 100%(T100)FO,respectively.A total of 840 juvenile yellow catfish with initial body weight of 2.12±0.01 g were randomly distributed into 6 groups with 4 replicates per group and 35 fish per replicate.Results showed that BSFO had no effects on final body weight(FBW),weight gain rate(WGR),specific growth rate(SGR),feed efficiency(FE),survival rate(SR),food intake rate(FIR),protein efficiency rate(PER),protein deposition rate(PDR),food intake(FI)of yellow catfish(P >0.05);The replacement levels had no significant effects on condition factor(CF),viscera index(VSI),hepatosomatic index(HSI),intraperitoneal fat index(IFI)(P>0.05);The replacement levels had no significant effects on albumin(ALB),low-density lipoprotein cholesterol(LDL-CH),triglyceride(TG),alanine aminotransferase(ALT),aspartate aminotransferase(AST),urea(UREA),globulin(GLO),lactate dehydrogenase(LDH),glucose(GLU),and total protein(TP)were no significant differently among the groups(P >0.05),Serum high-density lipoprotein cholesterol levels showed a trend of increasing first and then decreasing with the replacement ratio increasing.T60 and T80 were significantly higher than control group(P <0.05).BSFO instead of FO had no significant effects on superoxide anion content,catalase(CAT)activity,superoxide dismutase(SOD)activity,and malondialdehyde(MDA)content in the serum of yellow catfish(P >0.05).The levels of interleukin-10(IL-10),interleukin-6(IL-6)and interleukin-8(IL-8)increased with the replacement level increasing.The concentration of IL-10,IL-6,and IL-8 in serum were increased was significantly higher than that of the control group When the replacements level exceed 40%.The apparent digestibility of dry matter,protein,fat,phosphorus and energy did not have a significant effect on the fish oil supplemented with BSFO(P>0.05).The apparent digestibility of calcium was significantly higher in T60 and T80 than T100(P<0.05).There was no significant difference between other groups(P >0.05);There was no significant difference of the crude protein,crude fat,water content,ash,calcium,and phosphorus contents among gruops(P >0.05).There was also no significant difference in liver lipid droplet area ratio between the yellow catfish(P>0.05).Liver biopsy results showed that stem edema and vacuolar degeneration occurred in liver sections of all groups.A small amount of red blood cells wereobserved in the central vein.Hepatocytes were swollen and the cytoplasm was unevenly stained.A small number of nuclei were located on the side of the cellswith no large area of necrosis.In summary,the complete replacement of FO with BSFO has no significant effects on the growth performance,physical index,body composition,apparent digestibility of nutrients,serum biochemical indicators,serum anti-oxidation index,and liver tissue structure.The concentrations of inflammatory cytokines in the serum are conducive to inhibiting inflammation and improving immunity.Therefore,the BSFO can be used as a complete replacement of fish oil in the yellow catfish feed.2.Effects of dietary fish oil replaced with black soldier fly larvae oil on fatty acid composition and lipid metabolism related genes expression of yellow catfish.The aim of this study was to study the effects of FO replaced with BSFO on the fat deposition and lipid metabolism-related gene expression in the yellow catfish.After the feeding experiment,the liver and muscle samples were collected for analyse.Results showed that the content of saturated fatty acids and monounsaturated fatty acids in muscle and liver increased with the replacement levels.The saturated fatty acids were significant higher as the replacement level exceeded 40% in muscle and 80% in liver,respectively(P <0.05).The monounsaturated fatty acids reached highest when the replacement level exceeded 60% in muscle and 40% in liver(P<0.05).However,the content of polyunsaturated fatty acids in muscle and liver were decreased as the replacement level increased,the polyunsaturated fatty acid in muscle was significantly lower than that of control group when the replacement level exceeded 60%,in the liver,each replacement group were significantly lower than those in control group(P <0.05).The total replacement of FO with BSFO had no significant effects on the mRNA expression levels of FATP,LPL,L-FABP,ACC?,FAS,HL,CAT,PPAR? and HSL in the liver(P >0.05),The expression levels of PPAR?,HSL,and LPL mRNA in the liver firstly increased and then decreased as the replacement level increasing.The mRNA expression of PPAR? and LPL in the T40 were significantly higher than those in the T100(P <0.05).The HSL mRNA expression in T60 was significantly higher than that in T100(P <0.05).In summary,the content of saturated fatty acids increasedand the polyunsaturated fatty acids decreased with the increasing replacement of BSFO in muscle and liver.The replacement level affected some lipid metabolism genes in the liver.Therefore,in order to avoid adverse effects on the muscle quality of yellow catfish,the replacement ratio should not exceed 40%.