Effect Of Chronic Dietary Cyanobacteria On Muscle Quality And Fat Metabolism In Goldfish(Carassius Auratus)

Toxic cyanobacterial blooms,which produce cyclic heptapeptide toxins known as microcystins,are worldwide environmental problems.On the other hand,the cyanobacteria protein(30-50%)has been recommended as substitute protein for aquaculture.The present laboratory study verified the feasibility of cyanobacteria protein substitution and risk assessment.Goldfish were fed diets supplemented lyophilised cyanobacteria powder for 16 weeks with the various doses:0%(control),10%,20%,30%and 40%.1.Proximate composition and Meat quality indexLow doses(10%and 20%)promoted growth whereas high doses(30%and 40%)inhibited growth.In cyanobacteria treated fish,the proximate composition of crude fat content and crude protein content decreased in 16 weeks;the saturated fatty acid(SFA)content significantly increased;the n-3 polyunsaturated fatty acid content,collagen content and muscle pH significantly decreased.Muscle fiber diameter and myofibril length were negatively correlation.Additionally,flavour compounds(e.g.,amino acids,nucleotides,organic acids and carnosine)changed significantly in the treated fish,and odour compounds geosmin and 2-methylisoborneol increased significantly.The estimated daily intake(EDI)of microcystins in muscle was close to or exceeded the World Health Organization(WHO)tolerable daily intake(TDI),representing a great health risk.Cyanobacterie is noasible for protein sources use in aquaculture.2.Oxidative damage of liver and fat metabolism enzymesLiver body increase significantly;alkaline phosphatase(AKP),lactate dehydrogenase(LDH)and aspartate transaminase(GOT)and alanine transaminase(GPT)increase significantly;malondialdehyde(MDA)increase significantly;Light microscopy of liver section from the back of goldfish showed that structural loss,sinus dilation and condensed chromatin existed widely;Fat metabolism enzymes:fatty acid synthase(FAS)and malic enzyme(ME)increase significantly,glucose-6-phosphate dehydrogenase(G6PD)declined significantly,lipoprotein lipase(LPL)and hepatic lipase(HL)first increase significantly but finally declined significantly.FAS mRNA significantly declined expression level,LPL and HL mRNA significantly increased expression level,ME and G6PD mRNA first declined expression level significantly but finally increased expression level significantly.3.Oxidative damage and kidney and hematological indicesUrea nitrogen(BUN)and creatinine(Cr)increase significantly;Light microscopy of kidney section from goldfish showed that,dilation of Bowman’s capsule,reduction of components in glomerular,Cell vacuolization and hemorrhage existed widely;Antioxidant enzymes:hydrogen oxidation enzymes(CAT)and superoxide dismutase(SOD)first increase significantly but finally declined significantly,glutathione(GSH)declined significantly,glutathione peroxidase(GPX)and malondialdehyde(MDA)increase significantly;Glutathione reductase(GR)and glutathione S transferase(GST)decreased significantly after a significant rise in first;Content of red blood cell count(RBC),hemoglobin(Hb),red blood cells deposited(Ht)declined significantly,white blood cell count(WBC)and blood sedimentation(ESR)increased significantly.Morphology of blood cells from the goldfish showed that,cell malformation,cell indentation,cell membrane dissolution,hemolysis,agglomeration,cell swelling,Nuclear overflowing and cytoplasm retraction existed widely.