| Duck egg is one of the important nutrition sources,the contents of yolk n-3 polyunsaturated fatty acids(n-3 PUFAs)and yolk cholesterol(TC)are crucial to the egg quality.A lot of studies were developed to improve the contents of yolk n-3 PUFAs and yolk TC by changing the percentage composition of fatty acids in diet.However,the regulation mechanism is complicated and has not been illuminated.Besides,few comprehensive articles related to egg quality,molecular regulation and gut microbiota were reported.In this study,different fats(tallow,rapeseed oil,flaxseed oil and fish oil)were add to basal diets to investigate their effects on egg quality,contents of yolk fatty acids and cholesterol of Shan Partridge Duck.In addition,Digital Gene Expression(DGE),quantitative real-time PCR(q-RT-PCR)and induction by 18C-fatty acids in duck hepatic cells were applied to explore the pathways how duck fatty acids and cholesterol were regulated and detect candidate genes related to n-3 PUFAs and cholesterol,preliminarily clarified the molecular mechanisms that dietary n-3 PUFAs improve the yolk PUFAs and decrease the yolk cholesterol.Meanwhile,to comprehensively study the effects of dietary fatty acids on Shan Partridge Duck,the effects of fish oil on intestinal morphology and microbiota were carried out.1 The effects of different fats on serum lipids,yolk fatty acids and cholesterol.A flock of 585 ducks with excellent reproductive capacity were divided into 5 groups,one group was the control group(C)and fed with basal diet,the other four groups were treatment groups and fed with tallow(T),rapeseed oil(R),flaxseed oil(FL)and fish oil(F),respectively.Each treatment had three subgroups,fed with 0.5%,1%or 2%corresponding fat,respectively.After a 28-d period,three eggs from each subgroup were collected for egg qualities,yolk PUFAs and cholesterol,and one serum sample from each subgroup was collected for serum lipids.Results showed that supplemental fat source and fat level had no effects on egg qualities.Proportions of yolk total cholesterol(TC),saturated fatty acids(SFAs),monounsaturated fatty acids(MUFAs)were reduced(P<0.001),while polyunsaturated fatty acids(PUFAs),ω-6 polyunsaturated fatty acids(n-6 PUFAs),ω-3 polyunsaturated fatty acids(n-3 PUFAs),Eicosapentaenoic Acid(EPA)and Docosahexaenoic Acid(DHA)were increased by fish oil,flaxseed oil or rapeseed oil.Effects of supplementation were detected in F,FL and R in increasing yolk EPA and DHA.It can be concluded that unsaturated fatty acids riched diets(fish oil,flaxseed oil and rapeseed oil)might increase yolk PUFAs,reduce yolk cholesterol,change serum lipid parameters.2 The molecular mechanism of the lipids regulation by fish oil and flaxseed oil on Shan Partridge Ducks.A digital gene expression(DGE)profiling analysis of duck livers based on integrated RNA-Seq de novo was employed to screen the different expressed genes in 2%fish oil group and 2%flaxseed oil group.Liver total mRNAs were extracted,reverse transcripted,and sequenced.Nine samples were pooled to do the RNA-Seq de novo assembly.A total of 55,426 Unigenes were assembled from 53.2 million clean reads by RNA-Seq de novo assembly.Among them,27,376 Unigenes revealed similarity to the existing protein sequences in public databases.DGE libraries were constructed from the three groups(three samples each group),and generated over 10 million clean reads per library,88%-92.05%of them were mapped to the reference de novo transcriptome.A total of 896 and 883 differentially expressed genes(DEGs)were identified in FL and F,respectively,compared to C,of which,36 and 25 DEGs were related to lipid metabolism pathways.Compared to C,flaxseed oil significantly reduced the expression of arachidonic acid(ARA)related genes,such as PTGS1 and CYP2U,linolenic acid(LA)related genes,such as CYPA3 and CYP2J,primary bile acid synthesis related genes,such as CYP8B1 and CYP7A1,and other fatty acid synthesis related genes,such as FASN and ACSL.Fish oil significantly reduced the expression of primary bile acid synthesis related genes and fatty acids synthesis related genes,such as CYP8B1,ACSL and FASN,and significantly increased the expression of LA related genes,such as CYP2C and CYP2J,fish oil also reduced the expression of ELVL2 and FADS2.This suggests that the regulatory mechanisms of lipid are different in fish oil and flaxseed oil treatment groups.The results enriched the genetic information of Shan partridge duck and provided molecular regulation fundation for illuminating the biology phenomenon that dietary fish oil and flaxseed oil increased yolk n-3 PUFAs and decreased yolk cholesterol.3 The effects of 18 C fatty acids on the transcription and expression of n-3 LCPUFAs synthesis related genes.Hepatic cells were isolated by a two-step collagenase perfusion method and cultured by a routine method for liver cells.Cell growth curve was measured by MTT,and liver cells were identified by Periodic Acid-Shiff stain(PAS)and immunochemistry of CK18.Cells were added a-linolenic acid(ALA,C18:3,200 μM)or stearic acid(SA,C18:0,200 μM)after culturing for 24 h.Total RNAs,proteins and fatty acids were extracted after 48 h of inducing.Q-RT-PCR,Two-dimensional electrophoresis(2-DE)and mass-spectrography were applied to detect the effects of 18 C fatty acids on the expression of n-3 LCPUFAs(n-3 Long-Chain Polyunsaturated Fatty Acids)synthesis related genes,proteins and fatty acids.The results showed that SA and ALA significantly reduced the transcription of ELOVL2 and FADS1,SA significantly increased the transcription of FADS2;Differentially expressed proteins that directly related to n-3 LCPUFAs synthesis were not detected by 2-DE-MS;SA has no significant effects on the contents of SFAs,MUFA,n-3 PUFAs,ALA,EPA,and DHA;ALA significantly increased the contents of n-3 PUFAs,ALA and EPA.The results indicated that 1)AIA could be transformed into EPA and DHA in liver cells,while SA could not be;2)Both ALA and SA changed the expression of n-3 LCPUFAs synthesis related genes,while the mechanism of increasing n-3 LCPUFAs needs further research;3)2-DE was not a appropriate method to analyze the proteins involved in lipids metabolism of duck liver cells.4 The effects of fish oil on Morphology and microbiota of different intestinal sections of Shan Partridge Ducks.The goal of this study was to determine the differences in morphology and microbiota among 5 intestinal sections(duodenum,jejunum,ileum,cecum and rectum)of Shan partridge ducks(Anas platyrhynchos).Histological staining and 16S rDNA V3-V4 region sequencing were applied to examine the morphology and microbiota of intestines.The highest ratio of villus height to crypt depth(VH/CD)was found in the ileum,followed by the rectum,whereas goblet cell count(GCC)was the highest in the rectum,and no differences were detected between the other sections.Dietary supplementation with fish oil significantly reduced the VH/CD in the ileum,but had no significant effects on the other intestinal sections.Operational taxonomic units(OTUs)were the lowest in the duodenum and the highest in the ileum,but supplementing with fish oil reduced the number of OTUs overall.Alpha diversity analysis indicated that the lowest microbiotic diversity occurred in the duodenum,and that fish oil significantly reduced the diversity of the rectal microbiota.Taxa of Lactobacillus,Clostridia,Megamonas and Campylobacterales were chosen for further analysis on the results of linear discriminant analysis coupled with effect size(LEfSe).The results indicated that dietary supplementation with 2%fish oil compromised intestinal morphology and reduced the richness and diversity of the microbiota as a whole.This study provided reliable evidences for comprehensively evaluating the intestinal microbiota of Shan partridge duck,also provided basic information for studying the effect of fish oil on intestinal function of Shan partridge duck.This study comprehensively examined the effects of dietary fats on digestive system,egg qualities and lipid metabolism.The results showed that dietary fats had no significant effects on egg qualities;fish oil,flaxseed oil and rapeseed oil significantly increased yolk PUFAs and reduced yolk total fats.2%fish oil had adverse effects on intestinal morphology and microbiota.The mechanisms of reducing yolk cholesterol and increasing yolk PUFAs between 2%fish oil and 2%flaxseed oil were different in LA metabolism and the synthesis of long-chain polyunsaturated fatty acids. |
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