Improving flesh quality of grass carp(Ctenopharyngodon idellus)by completely replacing dietary soybean meal with yellow mealworm(Tenebrio molitor)

In order to find viable alternative protein sources for aquaculture,we evaluated the effect of partial or complete replacement of dietary soybean meal with yellow mealworm(TM)on the flesh quality of grass carp.In this study,180 grass carp(511.85±0.25 g)were fed 3 experimental diets in which 0%(CN),30%(YM30)and 100%(YM100)dietary soybean meal was replaced by TM for 90 d.The results showed that growth performance,biological parameters and serum antioxidant capacity of grass carp were not affected by dietary TM(P>0.05).Both muscle and whole body crude protein were obviously promoted with the increase of dietary TM(P<0.05),and the concentration of heavy metal in muscle was not influenced(P>0.05),indicating that food safety was not influenced by TM.Dietary TM improved muscle textural characteristics by elevating adhesiveness,springiness and chewiness in YM100(P<0.05).In addition,the muscle tenderness was significantly increased by declining the shear force(P<0.05).The muscle fiber density in YM30&YM100 and length of dark bands and sarcomeres in YM100 were obviously increased(P<0.05).The expression of myf5,myog and myhc exhibited a significant upward trend with the increase of dietary TM(P<0.05),which promoted fiber density,length of sarcomere and texture of grass carp muscle.According to the results of metabolomics,the arachidonate(ARA)and eicosapentaenoic acid(EPA)were notably elevated in YM30 and YM100,which indicated that the improvement of flesh quality of grass carp may contribute to the dietary TM influence on muscle lipid metabolism,especially the polyunsaturated fatty acids.In conclusion,TM can completely replace dietary soybean meal and improve the nutritional value of grass carp.

Assessment of black soldier fly(Hermetia illucens)larvae meal as a potential substitute for soybean meal on growth performance and flesh quality of grass carp Ctenopharyngodon idellus

A 90-day feeding trial was conducted to assess the effects of black soldier fly larvae meal(BSFLM)as a replacement for soybean meal(SM)on growth performance and flesh quality of grass carp.A total of 420grass carp(299.93±0.85 g)were randomly divided into 7 groups(triplicate)and fed 7 diets with SM substitution of 0%(SM,control),15%(BSFLM15),30%(BSFLM30),45%(BSFLM45),60%(BSFLM60),75%(BSFLM75)and 100%(BSFLM100)by BSFLM.The growth performance of grass carp in the BSFLM75 and BSFLM100 groups were significantly lower compared to other groups(P<0.05).The mid-gut villus height was the lowest in the BSFLM100 group(P<0.05).Muscle nutritional value was improved due to increased DHA(docosahexaenoic acid),EPA(eicosapentaenoic acid),total HUFA(highly unsaturated fatty acids)and glycine levels,and reached the optimum in the BSFLM100 group(P<0.05).According to the results of principal component analysis and weight analysis of muscle texture and body color,all the BSFLM diets except BSFLM15 could improve muscle texture and body color and reached the optimum level in the BSFLM100 group.Muscle drip loss and hypoxanthine content were the lowest and muscle antioxidant capacity was the highest in the BSFLM75 group,and water-and salt-soluble protein contents reached the optimum level in the BSFLM60 group(P<0.05).Dietary BSFLM significantly reduced muscle fiber area and diameter,and increased muscle fiber density and the proportion of small fiber(diameter<20μm)(P<0.05).Additionally,sarcomere lengths in the BSFLM75 and BSFLM100 groups were significantly higher than that in the SM group(P<0.05).The m RNA relative expression levels of Myo D,Myf5,My HC and FGF6b were remarkably up-regulated at an appropriate dietary BSFLM level(P<0.05).In conclusion,BSFLM could replace up to 60%SM without an adverse effect on growth performance and improve the flesh quality of grass carp.The optimum levels of dietary BSFLM were 71.0 and 69.1 g/kg diet based on the final body weight and feed conversion ratio.The flesh quality was optimal when dietary SM was completely replaced with BSFLM(227 g/kg diet).