Supplementation of Yeast Extract to Practical Diet Improves the Growth, Anti-Oxidative Capacity and Intestinal Morphology of Shrimp Litopenaeus vannamei

Two control diets based on the commercial formula were designed to contain high(27%,D1)and low(22%,D2)levels of fish meal,respectively.Into D2,500,1000 and 1500 mg kg 1 of yeast extract were added,respectively,yielding three experimental diets(YE1 through YE3).Shrimp(initial body weight 0.30 g±0.02 g)were fed with the experimental diets,five tanks each diet and 30 shrimp individuals each tank,for 8 weeks,and then challenged with Vibrio parahaemolyticus.The results showed that the specific growth rate(SGR)of shrimp in D2 was significantly lower than that of shrimp in D1(P<0.05).The SGR of shrimp in YE3 was similar to that of shrimp in D1.The feed intake of shrimp was similar between D1 and D2.The feed conversion ratio and protein efficiency ratio of shrimp were similar among all diets(P>0.05).YE significantly improved the activity of glutathione S-transferase.The concentration of glutathione(GSH)and the total serum anti-oxidative capacity(T-AOC)of D1 were significantly higher than those of shrimp feeding other diets(P<0.05).The content of serum malondialdehyde of shrimp feeding YE2 and YE3 was signifi-cantly lower than that of shrimp feeding D2(P<0.05).The thickness of intestine muscular layer of shrimp feeding YE1 and YE2 was similar to that of shrimp feeding D1.The shrimp feeding YE1 showed the highest villus height of intestine among all groups.The cumulative mortality after challenging was similar among all groups(70.00%86.67%)(P>0.05).In conclusion,1000 1500 mg kg 1 of YE was suggested to be supplemented into the practical diets to improve the growth,anti-oxidative capacity and intestinal mor-phology of shrimp L.vannamei.

A new insight on copper:Promotion of collagen synthesis and myofiber growth and development in juvenile grass carp(Ctenopharyngodon idella)

Copper(Cu)is a trace element,essential for fish growth.In the current study,in addition to growth performance,we first explored the effects of Cu on collagen synthesis and myofiber growth and development in juvenile grass carp(Ctenopharyngodon idella).A total of 1080 fish(11.16±0.01 g)were randomly divided into 6 treatments(3 replicates per treatment)to receive five doses of organic Cu which were Cu citrate(CuCit)at 0.99(basal diet),2.19,4.06,6.15,and 8.07 mg/kg,and one dose o inorganic Cu(CuSO_(4)·5H_(2)O at 3.15 mg/kg),for 9 weeks.The results showed appropriate Cu level(4.06 mg kg)enhanced growth performance,improved nutritional Cu status,and downregulated Cu-transporting ATPase 1 mRNA levels in the hepatopancreas,intestine,and muscle of juvenile grass carp.Meanwhile collagen content in fish muscle was increased after Cu intake,which was probably due to the following pathways:(1)activating CTGF/TGF-β1/Smads signaling pathway to regulate collagen transcription;(2upregulating of La ribonucleoprotein domain family 6(LARP6)mRNA levels to regulate translation initiation;(3)increasing proline hydroxylase,lysine hydroxylase,and lysine oxidase activities to regulate posttranslational modifications.In addition,optimal Cu group increased myofiber diameters and the frequency of myofibers with diameter>50μm,which might be associated with upregulation of cyclin B cyclin D,cyclin E,proliferating cell nuclear antigen,myogenic determining factor(MyoD),myogenic factor 5,myogenin(MyoG),myogenic regulatory factor 4 and myosin heavy chain(MyHC)and down regulation of myostatin mRNA levels,increasing protein levels of MyoD,MyoG and MyHC in fish muscle Finally,based on percentage weight gain(PWG),serum ceruloplasmin(Cp)activity and collagen conten in fish muscle,Cu requirements were determined as 4.74,4.37 and 4.62 mg/kg diet(CuCit as Cu source of juvenile grass carp,respectively.Based on PWG and Cp activity,compared to CuSO_(4)·5H_(2)O,the efficacy of CuCit were 131.80%and 115.38%,respectively.Our findings provide new insights into Cu supple mentation to promote muscle growth in fish,and help improve the overall productivity of aquaculture.

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.

Roles of dietary taurine in fish nutrition

Taurine is a conditionally essential amino acid in fish nutrition.The present study addressed the practical application of examining published data on fish nutrition over the past 20 years,emphasizing the topic of taurine by using computational tools and their applications.According to the published articles,an increased linear growth of research occurred,with Japanese flounder being the most examined fish species.Dietary taurine supplementation has several beneficial effects in fish nutrition,such as survival,growth,feed utilization,protein and energy retention,intermediate metabolism,anti-oxidation,anti-stress,disease resistance,muscle texture and reproductive performance.Also,there are negative effects in some species.Dietary taurine exerted effects on several gene expressions and enzyme activities;these are important in taurine metabolism in fish.These genes and enzymes included taurine transporter(TauT),cysteine dioxygenase(CDO),cysteamine dioxygenase(ADO),cysteine sulfonate decarboxylase(CSD)and pretrypsinogen(Ptry).Plant protein-based diets with taurine supplementation are recommended because of the absence of taurine in plani protein.