Effects Of A Compound Chinese Medicine Supplementation In Diets On Growth Performance,Meat Quality And Resistance To Bacteria Infection For Hybrid Snakehead(Channa Maculate ♀ × Channa Argus ♂)

With the rapid development of artificial culturing, hybrid snakehead(Channa maculate♀ × Channa argus♂), a high quality carnivorous freshwater fish, has become an important freshwater fish species in China in recent years. However, the rising levels of culturing density and feeding rate of high protein and energy feed has caused series of problems such as nutritional metabolic disorders, frequent occurrence of diseases and the meat quality declining in hybrid snakehead, which affects the commercial value of this species. In view of the problems, this study investigated the effects of a compound Chinese herbal medicine(CCM) on growth, meat quality and resistance to Aeromonas schubertii infection of hybrid snakehead. The main study contents and results are presented as follows:(1) Biological characteristics and drug susceptibility of Aeromonas schubertii WL-4isolated from snakehead. In this study, A. schubertii strain WL-4 which was isolated from the hybrid snakehead was analyzed in relation with its physiology and biochemistry characteristics, its growth characteristics and virulence factors, and its susceptibility was tested against 20 antibiotics. Its physiology and biochemistry characteristics were tested by using bacterial biochemical identification instrument and its growth situation was analyzed under different temperatures, salinities and pH values. The results of growth characteristics showed that the WL-4 strain’s optimum growth temperature was 30 ℃, optimal salinity was 5 and optimum pH was 7. In addition, the WL-4 strain exhibited virulence to snakeheads(25 ± 5) g in experimental challenges with LC50 being 1.2 × 106 CFU/mL. The WL-4 strain was positive for hemolytic activity, elastase and lipase activity by phenotypic determination. Susceptibility tests, which detected the minimum inhibition concentration(MIC) of 20 antibacterial agents by trace double dilution method, showed that the strain WL-4 was susceptible to doxycycline, neomycin, ampicillin and so on, but resistant to sulfonamides, florfenicol, thiamphenicol and other commonly used drugs in water production. In conclusion, biological characteristics of the WL-4 strain were consistent with the occurrence of the disease with white spots in snakeheads’ internal organs which werecausedbya.shubertii.inaddition,theresultsofantibacterialsusceptibilitytestsmayhaveanappliedvalueinthecontrolofa.shubertiiinfectionagentsinaquaculture.(2)effectsofccmsupplementationindietsontheresistancetoa.schubertiistrainwl-4’sinfectionforhybridsnakehead.experimentaldietswith0.0%(control),0.5%,1.0%,1.5%and2.0%ccmsupplementationwerefedtojuvenilehybridsnakeheadfor105days.theresistanceofhybridsnakeheadtothestrainwl-4infectionwasinvestigatedbythemethodofartificialinfection,andserumlysozyme,superoxidedismutase,peroxidase,alkalinephosphataseandnitricoxideactivitiesweredetected.resultsshowedthatsupplementationsof0.5%,1.0%and1.5%ccmindietsimprovedtheresistancetothestrainwl-4infectiontodifferentdegrees,andtherelativeimmuneprotectionratewasrespectively68.9%,37.8%and84.4%;theantiviraleffecthassomerelationswiththeimmuneorgandevelopmentandnon-specificimmuneparameters.(3)effectsofccmsupplementationindietsongrowthperformanceandmeatqualityofhybridsnakehead.toinvestigatetheeffectsofccmsupplementationongrowthperformanceandmeatqualityofhybridsnakehead,juvenilehybridsnakehead(initialbodyweightof30.52±0.31g)werefedonexperimentaldietsaddedwith0.0%(control),0.5%,1.0%,1.5%,and2.0%ccmfor45days.theresultsshowedthatthehighestgrowthgainrateandspecificgrowthratewasachievedinfishon2.0%ccm,whichwas28.7%and17.9%higherthanthatofcontrolgroup(p<0.05%).organsindexandspleenindexwasnotsignificantlydifferentamonggroups,whiletheliverindexof0.5%,1.0%,1.5%and2.0% group was 15.4%(P<0.05%), 9.0 %(P>0.05%), 12.4 %(P<0.05 %) and 10.2 %(P<0.05 %) lower than that of control group. Condition factor of 1.0 %, 1.5 % and 2.0 %group was 5.5 %(P<0.05%), 4.4 %(P<0.05%) and 4.4 %(P<0.05%) higher than that of control group, while it was not significantly different between 0.5 % group and control group(P>0.05). No significant difference in muscle moisture, crude ash content and crude protein was observed between different groups(P>0.05), but the crude fat content of muscle and liver were significantly lower than that of control group. Higher levels of total free amino acid(TFAA) and delicious amino acid(DAA) in CCM supplemented groups were observed compared with those of control(P<0.05). The highest level of TFAA and DAA were achieved in group 0.5 %(P<0.05), which was 26.1 % and 30.0 % higher than that of control group. CCM supplementation in diets significantly decreased muscle fiber diameter(P<0.05). Muscle drip loss rate was significantly decreased in 0.5 % and 1.0 %groups(P<0.05), which was 5.6 % and 8.9 % lower than that of control group, but 1.5 %and 2.0 % groups were no significantly with the drip loss rate of control group(P>0.05). In conclusion, high level of CCM supplementation in diet(2.0 %) has beneficial effects on enhancing growth and reducing lipid deposition in muscle and viscer for snakeheads, while low and middle levels(0.5 %, 1.0 %,) were helpful in increasing TFAA and DAA content in muscle and decreasing muscle fiber diameter and drip loss rate to improve the meat quality.The results of this study suggested that middle and low levels(1.5 %, 1.0 %, 0.5 %) of CCM supplementation in diets improved the meat quality of hybrid snakehead by increasing the total free amino acids and flavor amino acids contents in muscle and reducing drip loss rate, diameter of muscle fiber and visceral fat deposition, which improve and have a certain protective effect from diseases at the same time. High level(2.0 %) of CCM supplementation in diets enhanced the grow performance and reduce lipid deposition in organs of hybrid snakehead. Above all, appropriate dosage of CCM supplementation in diets has beneficial effects on improving the meat quality and enhancing the ability to resist bacteria infection for snakeheads, which had certain application value in healthy and safety aquaculture of hybrid snakeheads. The results also provide a theoretical basis for the application of the CCM in improving the meat quality and enhancing the immunity of the aquatic animals.