| The studies were conducted to evaluate dose-response effects of attractant of four plant flavors(thymol,carvacrol,eugenol and cinnamic)by ball maze on juvenile Pelteobargrus fulridraco.The optimal concentrations of four flavors were identified by fish collections respectively,and then the best flavor(thymol)selected among four flavors was made into effervescent tablet for test the effects of different formulations on Pelteobargrus Fulridraco.The effect of the best flavor on P.Fulridraco was evaluated with weight gain rate(WGR)after 56 days feeding trial.Finally acording to NPY(Neuropeptide Tyrosine)gene expression levels in brain of P.Fulridraco in starvation experiment,which could be the best index to explore the effect of flavor on P.Fulridraco attractant.The results were shown as followingAccording to the single-factor design,the fish collections were used to evaluate the attractive effects of four kinds of flavor(thymol,carvacrol,eugenol and cinnamic)on juvenile P.Fulridraco.The results showed thymol,carvacrol and cinnamic aldehyde had positive attractant effect,which the optimum concentration were 0.0357g/ml,0.0214g/ml,0.0081g/ml respectively.Thymol was best attractant on P.fulridraco larvae among four plant flavors,However which could also cause food lure inhibition when the concentration was too high.Eugenol had no significant effect among dietary different supplement groups.The thymol of 0.0375 g/ml was selected to make effervescent tablets for different formulations of comparative test.It was concluded that the flavor effervescent tablet had the shortest reaction time and the largest number of gathered fish.According to the results,different concentrations of thymol(75mg/kg,150mg/kg,250mg/kg,500mg/kg and 1000mg/kg)were added into the feed as the experimental groups which were feeding to 4.45±0.58 g juvenile P.Fulridraco.An-8-week feeding trial results showed between P.Fulridraco larvae weight gain(Y)and dietary thymol supplementation(X)expressed by quadratic equations Y =-0.0007X2 +107.08X+0.7963(R2 = 0.7772).According to the quadratic equation,when dietary supplement of thymol was 568.8 mg/kg,larvae could acquire the maximum weight gain.As 95% confidence level according to Jobling model,the confidence interval were between 414.5mg/kg and 723.1mg/kg,that is to say,when the additive amount of thymol reached 414.5mg/kg,significant weight gain effect can be achieved.Semi-quantitative PCR technique was utilized to detect the expression quantity of NPY gene in all tissues of P.Fulridraco,and the result showed that NPY gene expression level in brain tissues of P.Fulridraco was far higher than that in other body tissues(p< 0.01).The feeds and thymol were respectively fed to hungry P.Fulridraco to detect the changes of NPY gene expression quantity in brain tissues.The results showed that 0.0357g/ml thymol could efficiently affect NPY gene expression of P.Fulridraco brains(p< 0.05)to promote the ingestion of P.Fulridraco. |
