| Cherry Valley ducks is a famous meat duck breed,well-known for fast growth,high feed conversion rate and low breeding costs.However,compared to other local breeds,meat ducks are characterized by rapid body fat deposition,especially in subcutaneous and abdominal.The market sales volume is affected by its greasy,nutrition strategy is considered as a possible way to control fat deposition and improve meat quality,supply the market with healthy and delicious duck products.Recent studies have found that resveratrol have hypolipidemic effects,it can improve meat quality of animals.Therefore,this study chose ducks as subjects,systematically investigate the effect of resveratrol on meat quality,try to find the key genes affecting lipid metabolism,interpret the possible metabolic pathways and mechanisms of resveratrol in reducing fat deposition in ducks.Expecting to provide a basis for the application of resveratrol in waterfowl farming,and lay a theoretical foundation for the nutritional regulation of meat quality.The study was divided into two parts:phenotypic study and mechanistic study.A total of 432 healthy 1-day-old Cherry Valley ducks（male）were assigned to 4 dietary treatments according to a completely randomized design,each treatment contains 6replicates,18 ducks per replicates.Four different levels of resveratrol were evaluated（0,150,300,450 mg/kg）for 42 days,the trial was divided into two stages:early stage（0-21d）and later stage（22-42d）.In the phenotypic study,growth performance,carcass trait,meat quality（meat trait,amino acid and fatty acid composition）,muscle characteristics and nutrient utilization were measured.Mechanistic studies focus on muscle development and glycolipid metabolism-related gene expression and lipidomics,with the main results as follows.1 Effect of resveratrol on growth performance,carcass trait and nutrient utilization of ducksThe objective of this experiment was to investigate the effects of different doses of resveratrol on growth performance,carcass trait and nutrient utilization of ducks,obtain the optimal supplemental dose of resveratrol in meat duck diet.The results showed that the addition of resveratrol significantly increased the ADG of ducks in the first stage（0-21 days）（P<0.05）;300 mg/kg resveratrol supplement significantly increased the ADG of ducks in the second stage（21-42 days）（P<0.05）;During whole trial period,the ADG showed a quadratic relationship with the resveratrol dose（P<0.05）.450 mg/kg resveratrol supplement showed a decreasing trend in FI,but the difference was not significant（P>0.05）.With the increase of resveratrol dose,the liver weight and abdominal lipid rate of the test ducks linearly decreased at 21-days-old and 42 days-old（P<0.05）;the whole intestinal apparent metabolic rate of Ca,crude ash,Ser and Leu linearly increased（P<0.05）and the ileal ADE,Ser,Val,Ile and Leu linearly increased（P<0.05）.It indicates that the addition of suitable doses of resveratrol can improve the growth performance of ducks and promote the digestion and absorption of nutrients.Considering factors such as body weight gain,feed intake and economic benefits,the appropriate dose of resveratrol be added to meat duck diet is 300 mg/kg.2 Effects of resveratrol on meat quality and muscle fiber characteristics of ducksThe effects of resveratrol on meat quality and muscle fiber characteristics of ducks were studied by slaughter performance determination and fiber characteristics analysis,aiming to lay a histological basis for clarifying the mechanism of nutritional regulation.The results showed that resveratrol supplement could significantly reduce muscle shear force of ducks,improve the composition of amino acids and fatty acids in muscle,change muscle fiber trait and improve meat quality.Compared to the control group,the addition of 450 mg/kg resveratrol reduced leg muscle drip loss by 16.32%（P<0.05）,300 mg/kg resveratrol supplement significantly reduced leg muscle shear force by 13.17%（P<0.05）.With increasing dose of resveratrol,breast muscle shear force linearly decreased（P<0.05）,breast muscle meat color a*24 h,b*24 h and crude protein content linearly increased（P<0.05）,leg muscle color L*45 min linearly decreased（P<0.05）and a*45min linearly increased（P<0.05）;His,Arg,Ile,Phe,NEAA,Hexic acid and palmitic acid in breast muscle linearly increased（P<0.05）,pentadecanoic acid and eicosanoic acid linearly decreased（P<0.05）.Tyr and Phe in leg muscle increased linearly（P<0.05）.Compared with the control group,the flavor amino acid content in breast muscle was significantly increased with 300 mg/kg and 450mg/kg resveratrol supplement（P<0.05）,and the content of valeric acid,myristic acid,pentadecanoic acid and arachidonic acid linearly decreased（P<0.05）.HE stained sections result showed that 300 mg/kg and 450 mg/kg resveratrol supplement significantly decrease breast muscle fiber diameters and cross-sectional areas than the control group（P<0.05）,and the 450 mg/kg resveratrol group showed the greatest muscle fiber density（P<0.05）.Real-time PCR result showed that 450 mg/kg of resveratrol supplement significantly up-regulated the gene expression of Myo D in the breast and leg muscles of duck（P<0.05）and down-regulated the expression of MSTN gene in the leg muscles.The addition of different doses of resveratrol significantly up-regulated the expression of PPARαgene in the leg muscle（P<0.05）.The results indicate that resveratrol improved the quality of duck meat by regulating the expression of genes related to muscle development,resulting in finer and denser muscle fibers,which led to a decrease in muscle shear force and an increase in tenderness.3 Effects of resveratrol on the lipid metabolism of ducksResveratrol was found to improve the lipid profile of ducks,and to regulate biochemical hormones level,enzyme activity and gene expression related to glucolipid metabolism.Compared with the control group,the addition of 300 mg/kg and 450 mg/kg of resveratrol significantly increased the levels of TG,trypsin,total lipase,LPL and T3 in 42-days-old ducks（P<0.05）,with the addition of resveratrol,the levels of serum glucagon at21-days-old,leptin,LDL-C and its ratio to HDL-C at 42-days-old linearly decreased（P<0.05）,and a quadratic change in T4 and FT4 at 21-days-old（P<0.05）.Compared with the control group,300 mg/kg of resveratrol supplement significantly down-regulated the mRNA expression of ACC in serum and SREBP-1 in liver（P<0.05）;450 mg/kg of resveratrol supplement significantly down-regulated the mRNA expression of FAS gene in serum and liver（P<0.05）,and up-regulated the mRNA expression of ADPN in serum（P<0.05）;The addition of 300 mg/kg and 450 mg/kg of resveratrol significantly down-regulated the mRNA expression of LPL in serum and PPARγin liver of ducks（P<0.05）,and up-regulated the mRNA expression of SIRT1 in serum and liver of ducks（P<0.05）.Different doses of resveratrol could significantly up-regulate the expression of Fox O1mRNA in liver of ducks（P<0.05）.Results indicate that resveratrol effectively reduces fat deposition,improves lipid profile,promotes lipid metabolism-related enzyme activity and hormone secretion through regulating lipid metabolism-related gene expression.4 Lipidomics-based study on the mechanism of resveratrol regulation of lipid metabolism in ducksLiver tissues from the control group and 450 mg/kg resveratrol groups were selected for lipidomics experiment.Total lipid metabolites were extracted and the absolute contents of lipid substances in the samples were calculated using ultra performance liquid chromatography-quadrupole time-of-flight mass spectrometry.50 different metabolites were screened out according to PLS-DA model and t test（P<0.05,VIP>1）.It is found that resveratrol significantly down-regulated the levels of 1 DG,1 PA,10 PC,1 PE,2 SM,5Sphingosine,and significantly up-regulated the levels of 2 Cer,2 PG,5 PE,and 21 TG.The glycerophospholipid metabolic pathway and sphingolipid metabolic pathway are the most important pathways through which resveratrol affects lipid metabolism in ducks.In conclusion,resveratrol improved the growth performance of ducks,promoted the digestion and absorption of nutrients,and improved the tenderness and taste of meat quality by altering muscle fiber characteristics,optimizing the ratio of amino and fatty acid composition.By up-regulating the gene expression of lipocalin in the liver,resveratrol promotes the metabolism of the ducks organism and regulates the insulin level.Moreover,it decreases the expression of LPL gene in the serum and reduces fatty acid uptake;by activating SIRT1,it increases the expression level of FOXO1 gene,and by down-regulating the expression of SREBP-1c and ACC gene,which inhibits the transcriptional regulation of FAS and de novo synthesis of fatty acids.It effectively reduced fat deposition and improved the TG and LDL-C composition of the lipid profile,affected the activity of tryptase and total lipase and the levels of glucagon,leptin,lipocalin,T3,T4 and FT4.It is highly likely that resveratrol regulates adipocyte apoptosis through the metabolic pathway of sphingolipids,and changes the metabolic network of glycerophospholipids by simulating energy restriction,leading to increased adiponectin secretion and decreased leptin level,and changing lipid profile and ultimately regulating fat deposition in ducks. |
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