Dietary isoleucine improved flesh quality,muscle antioxidant capacity,and muscle growth associated with AKT/TOR/S6K1 and AKT/FOXO3a signaling in hybrid bagrid catfish(Pelteobagrus vachelli♀×Leiocassis longirostris♂)

Background:Muscle is the complex and heterogeneous tissue,which comprises the primary edible part of the trunk of fish and mammals.Previous studies have shown that dietary isoleucine(Ile)exerts beneficial effects on growth in aquatic animals.However,there were limited studies regarding the benefits of Ile on fish muscle and their effects on flesh quality and muscle growth.Thus,this study was conducted to explore whether dietary Ile had affected flesh quality and muscle growth in hybrid bagrid catfish(Pelteobagrus vachelli♀×Leiocassis longirostris♂).Methods:A total of 630 hybrid fish,with an initial average body weight of 33.11±0.09 g,were randomly allotted into seven experimental groups with three replicates each,and respectively fed seven diets with 5.0,7.5,10.0,12.5,15.0,17.5,and 20.0 g Ile/kg diets for 8 weeks.Results:In the present study,we demonstrated that Ile significantly:(1)increased muscle protein and lipid contents and the frequency distribution of myofibers with≤20μm and≥50μm of diameter;(2)improved pH value,shear force,cathepsin B and L activities,hydroxyproline content,resilience,cohesiveness,and decreased cooking loss,lactate content,hardness,springiness,gumminess,and chewiness;(3)decreased reactive oxygen species(ROS),malondialdehyde(MDA),and protein carbonyl(PC)contents,GCLC and Keap1 mRNA levels,and up-regulated CuZnSOD,CAT,GPX1a,GST,and Nrf2 mRNA levels;(4)up-regulated the insulin-like growth factor 1,2(IGF-1,IGF-2),insulin-like growth factor 1 receptor(IGF-1R),proliferating cell nuclear antigen(PCNA),Myf5,Myod,Myog,Mrf4,and MyHC mRNA levels,and decreased MSTN mRNAlevel;(5)increased muscle protein deposition by activating AKT-TOR-S6K1 and AKT-FOXO3a signaling pathways.Conclusion:These results revealed that dietary Ile improved flesh quality,which might be due to increasing nutritional content,physicochemical,texture parameters,and antioxidant ability;promoting muscle growth by affecting myocytes hyperplasia and hypertrophy,and muscle protein deposition associated with protein synthesis and degradation signaling pathways.Finally,the quadratic regression analysis of chewiness,ROS,and protein contents against dietary Ile levels suggested that the optimal dietary Ile levels for hybrid bagrid catfish was estimated to be 14.19,12.36,and 12.78 g/kg diet,corresponding to 36.59,31.87,and 32.96 g/kg dietary protein,respectively.

Effects of Dietary Protein and Temperature on Growth and Flesh Quality of Songpu Mirror Carp

The study was conducted to demonstrate the effects of dietary protein and water temperature on growth and flesh quality of Songpu mirror carp （Cyprinus carpio） at an initial weight （165.24±5.08） g. Practical diets were formulated to contain five protein levels （29.12%, 31.46%, 34.49%, 38.17%, and 40.13%）, and each diet was randomly assigned triplicate groups of 15 fishes at three temperatures （18℃, 22℃, and 26℃） in the recirculation system. Fishes were fed twice daily to apparent satiation for 56 days. Results indicated that fishes had higher weight gain rate at 22℃ and 26℃ than that at 18℃ （P〈0.05）, but there were no significant differences between 22℃ and 26℃ （P〉0.05）. Based on the weight gain rate, dietary protein level 29.12% could meet the requirement of the body at 18℃, 22℃, or 26℃. Crude protein, crude lipid, moisture and ash of muscle had no significant differences among those treatments （P〉0.05）. pH （after 24 h） of muscle was the highest at 18℃ and the lowest at 22℃ （P〈0.05）, but no differences were observed among different protein level groups at each temperature （P〉0.05）. No significant differences on shear force, water holding capacity, collagen, glycogen and lactate among all the treatments were found （P〉0.05）. It was concluded that when C. carpio fed to apparent satiation, the growth mainly depended upon temperature. Dietary protein could not significantly affect flesh quality, but temperature significantly affected pH of muscles. A dietary protein level 29.12% could meet the requirement of the body at 18℃, 22℃, or 26℃.

Partial replacement of soybean meal by yellow mealworm(Tenebrio molitor)meal influences the flesh quality of Nile tilapia(Oreochromis niloticus)

This study investigated the effects of yellow mealworm meal(YM)replacing soybean meal(SBM)at different proportions(0%,15%,30%and 45%,referred as YM0,YM15,YM30 and YM45,respectively)on the flesh quality of Nile tilapia.A total of 360 fish(70.0±0.12 g)were randomly divided into 4 groups(3 tanks per group).Fish were fed the experimental diet twice daily for 10 wk.The results showed that muscle protein content significantly decreased in YM30 and YM45,while the lipid content significantly decreased in YM45(P<0.05).The essential amino acids and flavor amino acids of the muscle were not affected by the YM substitution,while saturated fatty acid content decreased in YM30 and YM45 compared with YM0(P<0.05).Fillets in YM45 had higher hardness,gumminess,and a higher proportion of thin myofibers(≤100μm,P<0.05)than those in other groups.Further analysis revealed that apoptosis and atrophy related genes were up-regulated,while the muscle antioxidant capacity decreased significantly in YM45(P<0.05),which may be related to the high acid value in YM45 diet.Our findings indicated that YM could replace up to 30%SBM without substantially altering the flesh quality.When the replacement ratio increased to 45%,the flesh quality would change.Special attention should be paid to avoid feed rancidity which may affect the flesh quality of fish.

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.

Slurry ice as an alternative cooling medium for fish harvesting and transportation:Study of the effect on seabass flesh quality and shelf life

The objective of the study was to investigate the efficiency of slurry ice during harvesting and transportation of European sea bass(Dicentrarchus labrax)to retain flesh quality and extend shelf life,compared with conventional flake ice.Fish was slaughtered and transported in different mixtures of slurry ice and conventional flake ice(C:slaughtered and transported in 100%flake ice-Control samples,SC:slaughtered in 100%slurry ice and transported in 100%flake ice,S50:slaughtered and transported in 50%slurry ice-50%flake ice,S100:slaughtered and transported in 100%slurry ice)and subsequently stored under controlled isothermal conditions at 0℃for shelf life modelling and flesh quality evaluation(proteolytic enzymes).The replacement of conventional flake ice with slurry ice as a slaughtering method led to improved quality stability during subsequent refrigerated storage and shelf life extension,in terms of microbial growth,flesh quality and sensory degradation of fish.Based on microbial growth,the shelf life of C samples was found to be 19 days,whereas the shelf life of S50/S100 and SC was 21 and 25 days,respectively,showing that the replacement of flake ice with slurry ice resulted in 2–6 days shelf life extension of whole sea bass stored at 0℃.The use of slurry ice at slaughter and flake ice in transportation was accompanied by low activities and late peaks of all four enzymes that is expected to lead to delayed proteolytic degradation and extended freshness.

Dietary ribose supplementation improves flesh quality through purine metabolism in gibel carp(Carassius auratus gibelio)

Since the aquaculture industry is currently observing a deterioration in the flesh quality of farmed fish,the use of nutrients as additives to improve the flesh quality of farmed fish species is a viable strategy.The aim of this study was to investigate the effect of dietary D-ribose(RI)on the nutritional value,texture and flavour of gibel carp(Carassius auratus gibelio).Four diets were formulated containing exogenous RI at 4 gradient levels:0(Control),0.15%(0.15RI),0.30%(0.30RI)and 0.45%(0.45RI).A total of 240 fish(150±0.31 g)were randomly distributed into 12 fibreglass tanks(150 L per tank).Triplicate tanks were randomly assigned to each diet.The feeding trial was carried out in an indoor recirculating aquaculture system for 60 d.After the feeding trial,the muscle and liver of gibel carp were analysed.The results showed that RI supplementation did not result in any negative impact on the growth performance and 0.30RI supplementation significantly increased the whole-body protein content compared to the control group.The contents of collagen and glycogen in muscle were enhanced by RI supplementation.The alterations in the flesh indicated that RI supplementation improved the texture of the flesh in terms of its water-holding capacity and hardness,therefore improving the taste.Dietary RI facilitated the deposition of amino acids and fatty acids in the muscle that contributed to the meaty taste and nutritional value.Furthermore,a combination of metabolomics and expression of key genes in liver and muscle revealed that 0.30RI activated the purine metabolism pathways by supplementing the substrate for nucleotide synthesis and thereby promoting the deposition of flavour substance in flesh.This study offers a new approach for providing healthy,nutritious and flavourful aquatic products.

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).

The influence of graded levels of available phosphorus on growth performance,muscle antioxidant and flesh quality of young grass carp(Ctenopharyngodon idella)

Growth, muscle composition, meat quality characteristics and antioxidant capacity in muscle of young grass carp(Ctenopharyngodon idella)(initial weight 282.9 ± 3.3 g) fed graded levels of phosphorus(1.0,2.5, 3.8, 5.6, 7.8 and 9.5 g/kg diet) for 8 wk were investigated. Results indicated that percentage weight gain, feed intake, feed efficiency, serum phosphorus and alkaline phosphatase were improved with optimal phosphorus supplementations(P < 0.05). Muscle protein content and water holding capacity were significantly elevated, while moisture, lipid and ash contents were significantly decreased with dietary phosphorus to a certain level(P < 0.05). The meat shear force value and hydroxyproline content were not influenced by different levels of phosphorus. Muscle anti-hydroxyl radical, superoxide dismutase, catalase, glutathione S-transferase activities and glutathione content were significantly improved(P < 0.05). Conversely, anti-superoxide anion, glutathione reducase and glutathione peroxidase activities were decreased(P < 0.05) with dietary phosphorus to a certain level. These results indicated that suitable dietary phosphorus improved growth performance, meat quality and muscle antioxidant capacity. Dietary available phosphorus requirement of young grass carp for percentage weight gain was4.0 g/kg diet.

Flesh quality of hybrid grouper(Epinephelus fuscoguttatus♀×Epinephelus lanceolatus♂)fed with hydrolyzed porcine mucosasupplemented low fishmeal diet

Iso-nitrogenous and iso-lipidic diets containing 0%,3%,6%,9%,and 12%hydrolyzed porcine mucosa(namely,HPM0,HPM3,HPM6,HPM9,and HPM12)were prepared to evaluate their effects on the growth performance,muscle nutrition composition,texture property,and gene expression related to muscle growth of hybrid groupers(Epinephelus fuscoguttatus\Epinephelus lanceolatus_).Groupers were fed to apparent satiation at 08:00 and 16:00 every day for a total of 56 days.It was found that the weight gain percentage in the HPM0,HPM3,and HPM6 groups did not differ(P>0.05).The cooking loss and drip loss of the dorsal muscle in the HPM3 group were lower than those in the HPM6 and HPM9 groups(P<0.05).The hardness and chewiness of the dorsal muscle in the HPM3 group were higher than those in the HPM0,HPM9,and HPM12 groups(P<0.05).The gumminess in the HPM3 group was higher than that in the HPM9 and HPM12 groups(P<0.05).The total essential amino acid content of the dorsal muscle in the HPM12 group was higher than that in the HPM0 group(P<0.05).The contents of total n-3 polyunsaturated fatty acid and total n-3 highly unsaturated fatty acid,as well as the ratio of n-3/n-6 polyunsaturated fatty acid in the dorsal muscle was higher in the HPM0 group than in all other groups(P<0.05).The relative expressions of gene myogenic factor 5,myocyte enhancer factor 2c,myocyte enhancer factor 2a,myosin heavy chain,transforming growth factor-beta 1(TGF-b1),and follistatin(FST)were the highest in the dorsal muscle of the HPM3 group.The results indicated that the growth performance of hybrid grouper fed a diet with 6%HPM and 27%fish meal was as good as that of the HPM0 group.When fish ingested a diet containing 3%HPM,the expression of genes TGF-β1 and FST involved in muscle growth were upregulated,and then the muscle quality related to hardness and chewiness were improved.An appropriate amount of HPM could be better used in grouper feed.

The role of vitamin E in polyunsaturated fatty acid synthesis and alleviating endoplasmic reticulum stress in sub-adult grass carp(Ctenopharyngodon idella)

Vitamin E(VE)is an essential lipid-soluble vitamin that improves the fish flesh quality.However,the underlying molecular mechanisms remain unclear.This study aimed to investigate the effects of VE on growth performance and flesh quality in sub-adult grass carp(Ctenopharyngodon idella).A total of 450fish(713.53±1.50 g)were randomly divided into six treatment groups(three replicates per treatment)and fed for nine weeks with different experimental diets(dietary lipid 47.8 g/kg)that contained different levels of VE(5.44,52.07,96.85,141.71,185.66,and 230.12 mg/kg diet,supplemented as dl-a-tocopherol acetate).Notably,the treatment groups that were fed with dietary VE ranging from 52.07 to230.12 mg/kg diet showed improvement in the percent weight gain,special growth rate,and feed efficiency of grass carp.Moreover,the treatment groups supplemented with dietary VE level of 141.71,185.66,and 230.12 mg/kg diet showed enhancement in crude protein,lipid,and a-tocopherol contents in the muscle,and the dietary levels of VE ranging from 52.07 to 141.71 mg/kg diet improved muscle pH24h and shear force but reduced muscle cooking loss in grass carp.Furthermore,appropriate levels of VE(52.07 to 96.85 mg/kg diet)increased the muscle polyunsaturated fatty acid content in grass carp.Dietary VE also increased the mRNA levels of fatty acid synthesis-related genes,including fas,scd-1,fad,elovl,srebp1,pparγ,and lxra,and up-regulated the expression of SREBP-1 protein.However,dietary VE decreased the expression of fatty acid decomposition-related genes,including hsl,cpt1,acox1,and ppara,and endoplasmic reticulum stress-related genes,including perk,ire1,atf6,eif2a,atf4,xbp1,chop,and grp78,and down-regulated the expression of p-PERK,p-IRE1,ATF6,and GRP78 proteins.In conclusion,dietary VE increased muscle fatty acid synthesis,which may be partly associated with the alleviation of endoplasmic reticulum stress,and ultimately improves fish flesh quality.Moreover,the VE requirements for sub-adult grass carp(713.53 to 1590.40 g)were estimated to be 124.9 and 122.73 mg/kg diet based on percentage weight gain and muscle shear force,respectively.