Metabolic rate and evaporative water loss in the silky starling （Sturnus sericeus）

To better understand the physiological characteristics of the silky starling(Sturnus sericeus), its body temperature(Tb), basal metabolic rate(BMR), evaporative water loss(EWL) and thermal conductance(C) elicited by different ambient temperatures(Ta)(5-30 °C) were determined in the present study. Our results showed that they have a high Tb(41.6±0.1 °C), a wide thermal neutral zone(TNZ)(20-27.5 °C) and a relatively low BMR within the TNZ(3.37±0.17 mL O2/g·h). The EWL was nearly stable below the TNZ(0.91±0.07 mg H2O/g·h) but increased remarkably within and above the TNZ. The C was constant below the TNZ, with a minimum value of 0.14±0.01 mL O2/g·h·°C. These findings indicate that the BMR, Tb and EWL of the silky starling were all affected by Ta, especially when Ta was below 20 °C and the EWL plays an important role in thermal regulation.

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.

Effect of dietary L-glutamate levels on growth,digestive and absorptive capability,and intestinal physical barrier function in Jian carp(Cyprinus carpio var.Jian)

The present study explored effects of L-glutamate(Glu)levels on growth,digestive and absorptive capability,and intestinal physical barrier functions of Jian carp(Cyprinus carpio).A total of 600 Jian carp(126.40±0.21 g)were randomly distributed into 5 groups with 3 replicates each,fed diets containing graded levels of Glu(53.4[control],57.2,60.6,68.4,and 83.4 g/kg)for 63 d.Results showed compared with control diet,feed intake and percent weight gain(PWG)in fish fed 83.4 g of Glu/kg diet were increased and feed conversion ratio in fish fed 68.4 g of Glu/kg diet was decreased(P<0.05).Similarly,body crude protein and lipid contents in fish fed 68.4 g of Glu/kg diet were higher(P<0.05).The activities of trypsin and chymotrypsin in the hepatopancreas and intestine,and amylase,alkaline phosphatase(AKP),Na^+,K^+-ATPase(NKA),and creatine kinase(CK)in intestine were higher in fish fed 68.4 g of Glu/kg diet(P<0.05).Dietary Glu(57.2 to 83.4 g/kg diet)decreased malondialdehyde(MDA)and protein carbonyl(PCO)contents in the intestine(P<0.05).The activities of catalase(CAT),glutathione peroxidase(GPx),and glutathione S-transferase(GST)in the hepatopancreas and intestine were higher in fish fed 60.6 and 68.4 g of Glu/kg diets(P<0.05).Intestinal the glutathione reductase(GR)activity and glutathione(GSH)content in fish fed 60.6,68.4,and 83.4 g of Glu/kg diet were increased(P<0.05).The GPx1 a,GST,and nuclear factor erythroid 2-related factor 2(Nrf2)mRNA expressions in the intestine were up-regulated in fish fed 60.6 and 68.4 g of Glu/kg diet(P<0.05).The zonula occludens protein-1(ZO-1),occludin1,and claudin3 mRNA expressions were also up-regulated in fish fed 83.4 g of Glu/kg diet(P<0.05).Fish fed 68.4 g of Glu/kg diet had higher levels of claudin 2,claudin7,and protein kinase C(PKC)mRNA(P<0.05).These results indicated that Glu improved frsh growth,digestive and absorptive ability,and intestinal physical barrier functions.Based on the quadratic regression analysis of PWG,and MDA of the hepatopancreas and intestine,the optimal dietary Glu levels were estimated to be 81.97,71.06,and 71.36 g/kg diet,respectively.

Cloning,expression pattern,and potential role of MAPKp38 and NF-κBp65 in response to lipopolysaccharide in yellow catfish(Pelteobagrus fulvidraco)

Mitogen-activated protein kinases(MAPK) and nuclear factor kappa B(NF-κB) pathways are considered to be two crucial intracellular signaling cascades in pro-inflammatory responses.In this study,we reported the coding sequences(CDS) of MAPKp38 and NF-κBp65 from yellow catfish.We also investigated the gene structure,expression patterns and functional role in yellow catfish.The CDS of MAPKp38 is1,086 bp encoding 361 amino acids(AA).The MAPKp38 protein has a long highly conserved serine/threonine protein kinases catalytic domain.The NF-κBp65 CDS is 1,794 bp,and the gene encodes 597 AA,with a Rel homology domain(RHD) which consists of a RHD-DNA-binding domain and an Ig-like,plexins,transcription factors(IPT) domain.Moreover,MAPKp38 and NF-κBp65 protein of bony fish and other vertebrates have a single clade.Quantitative real-time PCR analysis revealed the presence of the MAPKp38 and NF-κBp65 transcript in 12 tissues of healthy yellow catfish.The highest expression levels of MAPKp38 and NF-κBp65 were detected in the heart and liver,respectively.Upon stimulation with an intraperitoneal injection of lipopolysaccharide(LPS),the expression levels of MAPKp38 and NF-κBp65 were up-regulated in the intestine.These results indicated that MAPKp38 and NF-κBp65 play important roles in mediating the response protection against LPS in yellow catfish.

An emerging role of vitamin D_(3) in amino acid absorption in different intestinal segments of on-growing grass carp(Ctenopharyngodon idella)

Vitamin D_(3)(VD_(3)),an essential nutrient for animals,has been demonstrated to stimulate the uptake of certain amino acids.However,the role of VD_(3) in the intestine,the primary site for digestion and absorption of nutrients,remains poorly characterized.Here,the grass carp(Ctenopharyngodon idella)was studied to assess the influence of different doses of VD_(3)(15.2,364.3,782.5,1,167.9,1,573.8,and 1,980.1 IU/kg)on growth performance,intestinal morphology,digestive absorption,amino acid transport,and potential signaling molecule levels in a feeding experiment.As a result,dietary VD_(3) improved growth performance,intestinal structure,and digestive and brush border enzyme activities.Additionally,most intestinal free amino acids and their transporters were upregulated after VD_(3) intake,except for Ala,Lys,Asp,Leu,solute carrier(SLC)7A7,SLC1A5,and SLC1A3 mRNA in different segments,Leu and SLC6A14 mRNA in the proximal intestine,and SLC7A5 mRNA in the mid and distal intestine.In the crucial target of rapamycin(TOR)signal pathway of amino acid transport,the gene and protein expression of TOR,S6 kinase 1,and activating transcription factor 4 were elevated,whereas 4E-binding protein 1 was decreased,further suggesting an advanced amino acid absorption capacity in the fish due to VD_(3) supplementation.Based on percentage weight gain,feed efficiency,and trypsin activity,the VD_(3) requirements of on-growing grass carp were estimated to be 968.33,1,005.00,and 1,166.67 IU/kg,respectively.Our findings provide novel recommendations for VD_(3) supplementation to promote digestion and absorption capacities of fish,contributing to the overall productivity of aquaculture.

Dietary isoleucine affects muscle fatty acid and amino acid profiles through regulating lipid metabolism and autophagy in hybrid catfish(Pelteobagrus vachelli ♀×Leiocassis longirostris ♂)

The present study explored the impacts of Ile on muscle fatty acid and amino acid profiles,lipid metabolism,and autophagy in hybrid catfish.Seven isonitrogenous(387.8 g/kg protein)semi-purified diets were formulated to contain 5.0(control),7.5,10.0,12.5,15.0,17.5,and 20.0 g Ile/kg diet respectively.The fish(initial weight of 33.11±0.09 g)were randomly assigned to 7 groups for a 56-day trial.Each group has 3 replicates with 30 fish per replicate,fed at 08:00 and 18:00 each day.Results showed that muscle protein and lipid,C14:0,C18:0,C22:0,C14:1,C18:1n-9,polyunsaturated fatty acid(PUFA),Arg,Ile,Ala,Cys,Gly,Tyr,essential amino acid(EAA),and total amino acid(TAA)contents and flavor amino acid(FAA)/TAA in muscle had positive linear and/or quadratic responses to dietary Ile levels(P<0.05).Fatty acid synthase(FAS),stearoyl-Co A desaturase(SCD),acetyl-Co A carboxylase(ACC),and lipoprotein lipase(LPL)activities had positive linear and/or quadratic responses,but carnitine palmitoyl transferase 1(CPT1)activity had a negative response with increasing dietary Ile levels(P<0.05).The m RNA expressions of FAS,SCD,ACC,LPL,fatty acid binding protein 4(FABP4),FATP1,sterol response element-binding protein 1c(SREBP-1c),sequestosome 1(SQSTM1),and adenosine 5’-monophosphateactivated protein kinase(AMPK)had positive linear and/or quadratic responses to dietary Ile levels(P<0.05).The m RNA expressions of hormone-sensitive lipase(HSL),CPT1,peroxisome proliferatoractivated receptor a(PPARa),PPARγ,uncoordinated 51-like kinase 1(ULK1),beclin1(Becn1),autophagy-related protein 9a(Atg9a),Atg4b,Atg7,autophagy marker light chain 3 B(LC3B),and SQSTM1in muscle had negative linear and/or quadratic responses to dietary Ile levels(P<0.05).The p-AMPK and ULK1 protein levels,and p-AMPK/AMPK were decreased by 12.5 g Ile/kg in the diet(P<0.05).Finally,SQSTM1 protein level had the opposite effect(P<0.05).The above results indicate that dietary Ile improves fish muscle fatty acid and amino acid profiles potentially via respectively regulating lipid metabolism and autophagy.The Ile requirement of hybrid catfish(33 to 72 g)were estimated to be 12.63,13.77,13.75,11.45,10.50,12.53 and 12.21 g/kg diet based on the regression analysis of protein,lipid,SFA,PUFA,FAA,EAA,and TAA muscle contents,respectively.