The Effects Of Dietary Fishmeal Replacement By Two New Non-food Protein Sources On The Quality Of Turbot(Scophthalmus Maximus)

In this study,turbot(S.maximus),an important mariculture fish widely cultivated in China,was used as the research object to investigate the effects of replacing fishmeal with defatted Tenebrio molitor meal(TM)and Clostridium autoethanogenum protein(C A)on quality related indexes of the turbot in an indoor seawater recycling culture system.The main research content and results of this paper are as follows:1.Effects of dietary fishmeal replacement by defatted Tenebrio molitor meal on the quality of turbot.Turbot with initial body weight of 150g were fed with fishmeal-based control diet(FM)and six experimental diets containing increasing levels of defatted TM to gradually replace fishmeal in control diet for 85 days.The substitution level of TM to fishmeal were set as 15%(TM15),30%(TM30)45%(TM45),60%(TM60),75%(TM75),and 100%(TM100).Samplings were conducted on the 56th day and the end of feeding trial.Dietary TM replaced up to 45%of fishmeal did not negatively impact growth performance,fillet yield,condition factor,and the nutritional value of flesh.However,from the view of hydroxyproline and collagen content and profile of fatty acids,TM more than or equal to 60%reduced the nutritional quality,but it could improve the health value of fatty acid by optimizing the proportion of unsaturated fatty acids.Human eyes cannot perceive the influence of TM on skin color.The cooked flesh sensory evaluation reported the odor and texture in mouth changed by TM at both sampling time but texture analyzer revealed that texture of raw flesh was only significantly affects by TM after 85 days’ feeding.The altered texture correlated with the changing of muscle microstructure.Except TM15,other diets with higher TM level decreased overall freshness,and the TM 15 diet may improved storage quality by delaying muscle softening.2.Effects of dietary fishmeal replacement by Clostridium autoethanogenum protein meal on the quality of turbot.Turbot with initial body weight of 180g were fed with fishmeal-based control diet(FM)and six experimental diets containing increasing levels of defatted CA to gradually replace fishmeal in control diet for 70 days.The substitution level of CA to fishmeal were set as 15%(CA15),30%(CA30),45%(CA45),60%(CA60),and 75%(CA75).The sampling was conducted after the breeding ended(day 0)and after storage at 4 C for three days(day 3).CA could replace up to 30%of fishmeal in diet and had no negative effect on growth performance and condition factor of turbot.However,CA reduced the fillet yield of turbot.The CA at a replacement level of more than 30%has a negative effect on the nutritional quality of muscle,as indicated by a reduction in the content of muscle hydroxyproline,collagen,and n-3 PUFA,but the proportion of unsaturated fatty acids was optimized.Dietary CA did not affect consumers’ purchase intention from the body color.Dietary CA affected the odor,flavor and texture in mouth of cooked flesh.Dietary CA improved the hardness of raw flesh,and the hardness is correlated with muscle histology parameters.Subsequently,gene expression analysis was performed on the groups with significant difference in histological parameters.The C A may change the muscle structure and thus improve the texture by down-regulating the expression of muscle growth-related genes(MyoD,MRF 4,Myf 5,Pax 7,IGF 1,IGF 2,TOR,Akt)and muscle protein turnover-related genes(MURF1,CtsL).The replacement level of CA more than or equal to 15%reduced the total freshness of turbot.