Effect Of Commercial Diet And Fresh Frozen Trash Fish On Growth, Antioxidant Capacity, Lipid Metabolism, Intestinal Bacterial Communities And Qualityof Hybrid Grouper (Epinephelus Fuscoguttatus ♀×Epinephelus Lanceolatus (?))

The study was aim to investigate theeffect of commercial diet and fresh frozen trash fish on growth,antioxidant ability,lipid metabolism,intestinal bacterial communities and quality of hybrid grouper(Epinephelus fuscoguttatus ♀×Epinephelus lanceolatus ♂) juveniles fish(initial average weight194.25±6.70) g was randomlydivided into 2 groups, each group containing 5271 fish was tested in triplicate,the two groups juvenilesfed commercial diet and freshfrozen trash fish, respectively,for 75 days undercommercial recirculating aquaculture system.The results showed that:(1)The weight gain(WGR),specific growth rate(SGR),feed conversion ratio(FCR)and condition factor(CF)of hybrid grouper juveniles fed with commercial diet group were significantly lower than fish fed with freshfrozen trash fishgroup(P<0.05).The hepatosmatic index(HSI), viscerosomatic index(VSI) were significantly higher than freshfrozen trash fish group(P<0.05),but the protein efficiency ratio(PER) and the survival rate(SR)had no significant differences between fresh frozen trash fish group and commercial diet group.The contents of total cholesterol(CHO), triglyceride(TG), low density lipoprotein cholesterol(LDL-C) in serum of commercial diets group were significantly decreased compared with fresh frozen trash fish group(P<0.05), the activities ofglutamic-pyruvic transaminase(GPT) and glutamic-oxaloacetic transaminase(GOT) in commercial feeds were significantly higher than fresh frozen trash fish group(P<0.05). There was an obvious decrease in levels of superoxide dismutase(SOD),total antioxidant capacity(T-AOC),catalase enzyme(CAT) and fatty acid synthase(FAS), and a significant increase in activity of lipoprotein lipase(LPL) was observed in commercial diet group, while the levels of malic dehydrogenase(MDH) and carnitine palmitoyltransferase-II(CPT-II) were not impacted by two diet(P > 0.05).(2)We builtthe 16 Sr RNA gene bank of diet,intestinal bacterial communities,bacterial communities of culture pond of hybridgrouper(Epinephelus fuscoguttatus♀×Epinephelus lanceolatus ♂) juveniles, designed specific primers to the variable areaof V3+V4 for 16 Sr RNA gene and through the high-throughput sequencing based on Illumina Hi Seq sequencing to compare the different construction among theirs.The results show that: the advantage intestinal bacterial communitiesof two treatment groupswere Proteobacteria(more than 60%), Photobacterium,Vibrio and Cetobacterium. Including that in the CF group,the abundance of Photobacterium was higher than the group FF,and the abundance of Vibrio and Cetobacterium was lower than the group FF. In the groupof WC,the advantage bacterial communities were Pseudoalteromonas(23.73%), Glaciecola(13.96%), Photobacterium(16.97%),Polaribacter(7.39%). In the groupof WF,the advantage bacterial communities were given proirity to the Lishizhenia(34.01%), Photobacterium(7.07%),Pseudoalteromonas(4.78%). Thecommercial diets were similar to theintestinal bacterial communitiesand bacterial communities of culture pondin two treatment groups.(3)Thecontent of lipid of muscle and whole body incommercial dietgroup was significantlydecreased than that ofthe fresh frozen trash fish group(P<0.05);thecontent of protein, ash, moisture had no significant difference(P>0.05).17 kinds of amino acids were determined in juveniles muscles with 9 kinds of essential amino acids and 4 kinds of delicious amino acids. The content ofthreoninearginine, glycine and cysteine in fresh frozen trash fish group were significantly higher than that of commercialdietgroup(P<0.05).The content of prolinewere significantly lower than that of the commercial diet group(P<0.05).The content of total essential amino acid, total amino acid and delicious amino acid in fresh frozen trash fish group were significantly higher than that of the commercial dietgroup(P<0.05). We analyzed the composition of fatty acid of muscle in two treatment groups and found the content of EPA and DHA in commercial diet group were significantly lower than that of the fresh frozen trash fish group(P<0.05).The content of polyunsaturated fatty acids(PUFA) and the EPA + DHA were significantly lower compared tofresh frozen trash fish group difference(P<0.05).The muscle of hardness, cohesiveness, springiness and chewiness of fresh frozen trash fish groupwere significantly higher than that of the commercial diet group(P<0.05),andthe content of IMP was significantly higher thanthat of thecommercial diet group(P<0.05).In conclusion, the juveniles of fresh frozen trash fish could grow fast, have a high antioxidant capacity of live. The commercial diets brought some stress on liver. two diet had effects on the bacterial communities of intestinal and culture pond.Thecommercial diet were similar to theintestinal bacterial communitiesand bacterial communities of culture pond in two treatment groups.