Palatability of Water-Soluble Extracts of Protein Sources and Replacement of Fishmeal by a Selected Mixture of Protein Sources for Juvenile Turbot（Scophthalmus maximus）

Poorpalatabilityisalimitingfactorforreplacingfishmealwithotherproteinsourcesinaquaculture.Thewater-solublemoleculeswithlowmolecularweightsarethemajordeterminantsofthepalatabilityofdiets.Thepresentstudywasconductedtoinvestigatethepalatabilityofwater-solubleextractsfromsingleproteinsource（singleextractpellets）andthemixtureoftheseextractswithdifferentproportions（blendedextractpellets）injuvenileturbot（Scophthalmusmaximus）.Thenaccordingtothepalatabilityofblendedextractpellets,anoptimalmixtureproportionwasselected,andanewproteinsourcemadefromrawproteinmaterialswiththeselectedproportionwasformulatedtoreplacefishmeal.Summarily,thepalatabilityofsingleextractpelletsforturbotwasdescendentfromfishmealtopet-foodgradepoultryby-productmeal,wheatglutenmeal,soybeanmeal,peanutmeal,meatandbonemeal,andcornglutenmeal.Subsequently,accordingtothepalatabilityofsingleextractpellets,52kindsofblendedextractpelletsweredesignedtotesttheirpalatability.Theresultsshowedthatthepelletspresentedremarkablydifferentpalatability,andtheoptimalonewasdiet52（wheatglutenmeal:pet-foodgradepoultryby-productmeal:meatandbonemeal:cornglutenmeal=1:6:1:2）.Thehighestingestionratio（thenumberofpelletsingested/thenumberofpelletsfed）was0.73±0.03,whichwasobservedinDiet52.Thenfiveisonitrogenous（52%crudeprotein）andisocaloric(20kJg-1grossenergy)dietswereformulatedbyreplacing0（control）,35%,50%,65%and80%offishmealwithNo.52blendingproportion.Aftera10-weeksfeedingtrial,aconsistentfeedintakewasfoundamongallreplacementtreatments.Replacementleveloffishmealupto35%didnotsignificantlyinfluencefinalbodyweight,specificgrowthrate,feedefficiencyratio,andproteinefficiencyratioofturbot.Therefore,thewater-solubleextractsofproteinsourcesplayanimportantroleinimprovingthepala