Unique feather color characteristics and transcriptome analysis of hair follicles in Liancheng White ducks.

Avian feather color is a fascinating trait, and the genetic mechanism of duck plumage formation is still in the preliminary stage. In this study, feather color of Liancheng White ducks was analyzed by determination of melanin content and RNA-seq analysis. In this research, 9 ducks from Mallards (n = 3), Liancheng White (n = 3) and Pekin ducks (n = 3) were used by high performance liquid chromatography (HPLC) and Masson-Fontana staining to reveal the difference of feather melanin content. RNA-seq from 11 hair follicle tissues (1- and 8-wk-old) of Liancheng White ducks (n = 5) and Pekin ducks (n = 7) was used to analyze the candidate genes for the feather melanin synthesis, and Immunofluorescence experiment was used to show the protein expression in 6 black- and white-feathered ducks. Pectorale, skin, liver, fat, brain, heart, kidney, lung, spleen of an 8-wk-old black-feathered Mallard were collected for candidate gene expression. The results showed that the contents of feathers, beak, web melanin in Liancheng White ducks were higher than in Pekin ducks (p < 0.05). Melanin within hair follicles was located in the barb ridge and hair matrix of black feather duck, also we found that TYRP1, TYR, SOX10 genes were differentially expressed between Liancheng White and Pekin ducks (p < 0.05), and these genes were mainly expressed showed in duck skin tissues. This study revealed the unique feather color phenotype of Liancheng White duck shedding light on the transcriptome that underlies it.

Cis-eQTLs in seven duck tissues identify novel candidate genes for growth and carcass traits.

BACKGROUND: Expression quantitative trait loci (eQTL) studies aim to understand the influence of genetic variants on gene expression. The colocalization of eQTL mapping and GWAS strategy could help identify essential candidate genes and causal DNA variants vital to complex traits in human and many farm animals. However, eQTL mapping has not been conducted in ducks. It is desirable to know whether eQTLs within GWAS signals contributed to duck economic traits. RESULTS: In this study, we conducted an eQTL analysis using publicly available RNA sequencing data from 820 samples, focusing on liver, muscle, blood, adipose, ovary, spleen, and lung tissues. We identified 113,374 cis-eQTLs for 12,266 genes, a substantial fraction 39.1% of which were discovered in at least two tissues. The cis-eQTLs of blood were less conserved across tissues, while cis-eQTLs from any tissue exhibit a strong sharing pattern to liver tissue. Colocalization between cis-eQTLs and genome-wide association studies (GWAS) of 50 traits uncovered new associations between gene expression and potential loci influencing growth and carcass traits. SRSF4, GSS, and IGF2BP1 in liver, NDUFC2 in muscle, ELF3 in adipose, and RUNDC1 in blood could serve as the candidate genes for duck growth and carcass traits. CONCLUSIONS: Our findings highlight substantial differences in genetic regulation of gene expression across duck primary tissues, shedding light on potential mechanisms through which candidate genes may impact growth and carcass traits. Furthermore, this availability of eQTL data offers a valuable resource for deciphering further genetic association signals that may arise from ongoing extensive endeavors aimed at enhancing duck production traits.

Genetic parameters and genomic prediction of growth and breast morphological traits in a crossbreed duck population.

Genomic selection (GS) has great potential to increase genetic gain in poultry breeding. However, the performance of genomic prediction in duck growth and breast morphological (BM) traits remains largely unknown. The objective of this study was to evaluate the benefits of genomic prediction for duck growth and BM traits using methods such as GBLUP, single-step GBLUP, Bayesian models, and different marker densities. This study collected phenotypic data for 14 growth and BM traits in a crossbreed population of 1893 Pekin duck × mallard, which included 941 genotyped ducks. The estimation of genetic parameters indicated high heritabilities for body weight (0.54-0.72), whereas moderate-to-high heritabilities for average daily gain (0.21-0.57) traits. The heritabilities of BM traits ranged from low to moderate (0.18-0.39). The prediction ability of GS on growth and BM traits increased by 7.6% on average compared to the pedigree-based BLUP method. The single-step GBLUP outperformed GBLUP in most traits with an average of 0.3% higher reliability in our study. Most of the Bayesian models had better performance on predictive reliability, except for BayesR. BayesN emerged as the top-performing model for genomic prediction of both growth and BM traits, exhibiting an average increase in reliability of 3.0% compared to GBLUP. The permutation studies revealed that 50 K markers had achieved ideal prediction reliability, while 3 K markers still achieved 90.8% predictive capability would further reduce the cost for duck growth and BM traits. This study provides promising evidence for the application of GS in improving duck growth and BM traits. Our findings offer some useful strategies for optimizing the predictive ability of GS in growth and BM traits and provide theoretical foundations for designing a low-density panel in ducks.

Embryonic growth and effect of embryonic age on quantitative and functional characteristics of duck primary hepatocytes.

Primary hepatocytes (PH) have been widely used in metabolic and disease-resistance mechanism research. However, hepatocyte isolation (HI) remains challenging in ducks. This study aimed to explore embryonic growth and the effect of embryonic age (EA) on the quantitative and functional characteristics of PH in ducks. For embryonic growth, the size and weight of the embryo and liver were determined from 6 to 28 EA (E6-E28, similar below). As EA increased, the corresponding size and weight grew significantly. Specifically, embryonic length varied from 12.5 mm to 133.0 mm, and liver width varied from 2.0 mm to 26.2 mm. Embryonic weight ranged from 0.259 g to 53.58 g, and liver weight ranged from 0.007 g to 1.765 g. Liver index initially decreased and then increased with a ratio ranging from 1.06 to 3.29%. For quantitative and functional characteristics, they were determined from E6 to E22, as there were no obvious liver features before E6 and few cells obtained after E22. The number of cells isolated in liver increased from E6 to E16 and then sharply decreased from E16 to E22. The viability remained relatively stable from E6 to E10 and then decreased from E12 to E22. The comprehensive intensity of hepatic glycogen was stronger at E8 and E14. Albumin expression increased markedly from E6 to E18 by qPCR, and the overall albumin expression was stronger at E8 and E14 by immunofluorescence assay. Hepatocyte purity exceeded 90% except for E20 and E22. During culture, cell clusters appeared after 24-h culture, which were identified as nonhepatocytes. The growth curve showed an initial increase in cell quantity followed by a decrease, another increase, and then remaining stable. In conclusion, EA had a significant effect on the quantitative and functional characteristics of PH, and the suitable EA for HI were E8 and E14. Considering better operability and quantity, E14 was the optimal EA, laying a solid foundation for further hepatocyte purification, nutrient metabolism, and disease-resistance mechanism explorations in ducks.

Effects of DHAV-3 infection on innate immunity, antioxidant capacity, and lipid metabolism in ducks with different DHAV-3 susceptibilities.

The aim of the experiment was to evaluate the status of innate immunity, oxidative status and lipid accumulation in ducklings exhibiting varying susceptibilities to DHAV-3 infection. In the experiment, ducklings with different DHAV-3 susceptibilities were used. Samples were collected at 6, 12, 15, and 24 h post infection (hpi), with 5 samples per time point. Plasma biochemistry, antioxidant enzyme activities, lipid content of liver and kidney were detected in the experiment. Elevated plasma level of total bilirubin, direct bilirubin, and creatinine indicated the injury of liver and kidney in susceptible ducklings (P < 0.05). The histopathological sections showed the injury in kidney. During the infection time, there was an increase in the concentrations of reactive oxygen species and oxidative damage markers (malondialdehyde and nitric oxide) in plasma of susceptible ducklings, particularly at 24 hpi (P < 0.05). Compared with the resistant ducklings, DHAV-3 infection resulted in a significant increase in the plasma total triglyceride (TG) level and a decrease in glucose level in susceptible ducklings. Gene expression of the innate immune response was both investigated in liver and kidney. In resistant ducklings, the expressions levels of pattern recognition receptors RIG-I, MDA5 remained constant. In contrast, the gene expressions peaked at 24 hpi in the susceptible ducklings. DHAV-3 infection promoted the expression of IFN, IL6, IL12ß, caspase-8 or caspase-9 in both liver and kidney of susceptible ducklings. In conclusion, DHAV-3 infection led to the mobilization of antioxidant defenses, alterations in lipid metabolism, and oxidative stress in susceptible ducklings during DHAV-3 infection.

Dietary riboflavin supplementation improves meat quality, antioxidant capacity, fatty acid composition, lipidomic, volatilomic, and proteomic profiles of breast muscle in Pekin ducks.

Our objective was to determine effects of supplemental dietary riboflavin on meat quality, antioxidant capacity, fatty acid composition, lipidomic, volatilomic, and proteomic profiling of duck breast muscle. The results showed that dietary riboflavin supplementation significantly increased growth performance, breast meat yield, intramuscular fat content, polyunsaturated fatty acid (PUFA), n3-PUFA, n6-PUFA, redness (a*), and pH24h, but decreased lightness (L*) and yellowness (b*). Furthermore, riboflavin supplementation significantly improved muscle antioxidant capacity based on various biochemical parameters. Lipidomic and volatilomic analyses revealed that riboflavin supplementation markedly increased breast meat phosphatidylglycerol and coenzyme Q contents and two favourable key odorants, citronellyl acetate and 3-(methylthio)-propanal. Proteomics analyses confirmed that riboflavin supplementation activated mitochondrial aerobic respiration, including fatty acid beta oxidation, the tricarboxylic acid cycle, and oxidative phosphorylation. In conclusion, supplementing duck diets with riboflavin enhanced breast meat quality, attributed to increases in antioxidant capacity and mitochondrial functions.

Changes in physical architecture and lipids compounds in skeletal muscle from Pekin duck and Liancheng white duck.

As a complex food, meat displays various biochemical properties that are determined to a great extent by physical architecture and lipid metabolites. Pekin duck and Liancheng white duck are elite breeds with distinct characteristics. Here, we explored the development of the muscle fibers from embryonic stage to 10-wk after birth, and muscle fibers grow slowly after 8-wk. We investigated the meat quality, ultrastructure, lipidomics profiling, and lipids spatial distribution of skeletal muscle at 8 wk. Pekin duck has lower Warner-Bratzler shear force (WBSF) (P < 0.05), high intramuscular fat (IMF) (P < 0.01), longer and wider sarcomere, and higher mitochondrial density (P < 0.001). Liancheng white duck with tighter collagen architecture. A total of 950 lipids from 6 lipid classes identified with lipidomics were analyzed, the levels of GP, GL, and PR were significantly higher in Pekin duck (P < 0.05), SL and ST were significantly higher in Liancheng white duck (P < 0.05). There were 333 significantly different lipids (|log2(Fold Change)| ≥ 1 and FDR < 0.05) screened, most lipids distributed in the muscle tissue were uniform, but some specifically distributed in connective tissue. To some extent, the results demonstrate the high lipid deposition capacity of Pekin duck and the high medicinal function of Liancheng white duck. Our study provides new insights into the relationship between skeletal muscle architecture and meat toughness, which increased the knowledge of lipidomic characteristics and provide a basis for duck meat authentication.

Strategies to improve genomic predictions for 35 duck carcass traits in an F2 population.

BACKGROUND: Carcass traits are crucial for broiler ducks, but carcass traits can only be measured postmortem. Genomic selection (GS) is an effective approach in animal breeding to improve selection and reduce costs. However, the performance of genomic prediction in duck carcass traits remains largely unknown. RESULTS: In this study, we estimated the genetic parameters, performed GS using different models and marker densities, and compared the estimation performance between GS and conventional BLUP on 35 carcass traits in an F2 population of ducks. Most of the cut weight traits and intestine length traits were estimated to be high and moderate heritabilities, respectively, while the heritabilities of percentage slaughter traits were dynamic. The reliability of genome prediction using GBLUP increased by an average of 0.06 compared to the conventional BLUP method. The Permutation studies revealed that 50K markers had achieved ideal prediction reliability, while 3K markers still achieved 90.7% predictive capability would further reduce the cost for duck carcass traits. The genomic relationship matrix normalized by our true variance method instead of the widely used [Formula: see text] could achieve an increase in prediction reliability in most traits. We detected most of the bayesian models had a better performance, especially for BayesN. Compared to GBLUP, BayesN can further improve the predictive reliability with an average of 0.06 for duck carcass traits. CONCLUSION: This study demonstrates genomic selection for duck carcass traits is promising. The genomic prediction can be further improved by modifying the genomic relationship matrix using our proposed true variance method and several Bayesian models. Permutation study provides a theoretical basis for the fact that low-density arrays can be used to reduce genotype costs in duck genome selection.

Metabolome-Based Genome-Wide Association Study of Duck Meat Leads to Novel Genetic and Biochemical Insights.

Meat is among the most consumed foods worldwide and has a unique flavor and high nutrient density in the human diet. However, the genetic and biochemical bases of meat nutrition and flavor are poorly understood. Here, 3431 metabolites and 702 volatiles in 423 skeletal muscle samples are profiled from a gradient consanguinity segregating population generated by Pekin duck × Liancheng duck crosses using metabolomic approaches. The authors identified 2862 metabolome-based genome-wide association studies (mGWAS) signals and 48 candidate genes potentially modulating metabolite and volatile levels, 79.2% of which are regulated by cis-regulatory elements. The level of plasmalogen is significantly associated with TMEM189 encoding plasmanylethanolamine desaturase 1. The levels of 2-pyrrolidone and glycerophospholipids are regulated by the gene expression of AOX1 and ACBD5, which further affects the levels of volatiles, 2-pyrrolidone and decanal, respectively. Genetic variations in GADL1 and CARNMT2 determine the levels of 49 metabolites including L-carnosine and anserine. This study provides novel insights into the genetic and biochemical basis of skeletal muscle metabolism and constitutes a valuable resource for the precise improvement of meat nutrition and flavor.

Genetic fine-mapping reveals single nucleotide polymorphism mutations in the MC1R regulatory region associated with duck melanism.

Birds are among the most colourful terrestrial vertebrates, with various plumage colours and patterns. We conducted a genome-wide association study (GWAS) on an intercross F2 population of Pekin ducks and mallards (n = 722) and identified a 1.57-Mb genetic region (Chr11: 20,176,480-21,750,101 bp) related to duck melanism. Fine mapping by linkage disequilibrium (LD) and FST analysis narrowed the final candidate region to a region of 22,500 bp (Chr11: 20,677,500-20,700,000 bp) including three coding genes, TCF25, MC1R and TUBB3. Combined with transcriptome and qRT-PCR analysis, MC1R was identified as the unique genetic locus responsible for black plumage in ducks, and it was significantly more highly expressed in the feather bulbs of black ducks. We also identified 52G > A (Chr11: 20,696,354G > A) and 376G > A (Chr11: 20,696,678G > A) mutations in the MC1R coding region that have been widely studied in ducks. In addition, structural variations (SVs) were screened by nanopore sequencing, and no significant SV was found to be associated with the duck black plumage trait. However, we identified four novel single nucleotide polymorphisms in the MC1R regulator region (Chr11: 20,678,412G > A, Chr11: 20,679,236G > A, Chr11: 20,692,496 A > G and Chr11: 20,692,791 A > G) that had a strong association with the black plumage phenotype of ducks and combined with potential changes in transcription binding affinities. The luciferase reporter gene assay demonstrated that Chr11: 20,678,412G > A and Chr11: 20,679,236G > A led to significant promoter activity changes. Our research emphasizes the importance of MC1R regulatory region mutation in determining the duck black plumage phenotype, and these results expand our understanding of the genetic mechanism underlying duck plumage colour.

Resequencing of a Pekin duck breeding population provides insights into the genomic response to short-term artificial selection.

BACKGROUND: Short-term, intense artificial selection drives fast phenotypic changes in domestic animals and leaves imprints on their genomes. However, the genetic basis of this selection response is poorly understood. To better address this, we employed the Pekin duck Z2 pure line, in which the breast muscle weight was increased nearly 3-fold after 10 generations of breeding. We denovo assembled a high-quality reference genome of a female Pekin duck of this line (GCA_003850225.1) and identified 8.60 million genetic variants in 119 individuals among 10 generations of the breeding population. RESULTS: We identified 53 selected regions between the first and tenth generations, and 93.8% of the identified variations were enriched in regulatory and noncoding regions. Integrating the selection signatures and genome-wide association approach, we found that 2 regions covering 0.36 Mb containing UTP25 and FBRSL1 were most likely to contribute to breast muscle weight improvement. The major allele frequencies of these 2 loci increased gradually with each generation following the same trend. Additionally, we found that a copy number variation region containing the entire EXOC4 gene could explain 1.9% of the variance in breast muscle weight, indicating that the nervous system may play a role in economic trait improvement. CONCLUSIONS: Our study not only provides insights into genomic dynamics under intense artificial selection but also provides resources for genomics-enabled improvements in duck breeding.

Genome-wide association studies demonstrate the genes associated with perimysial thickness in ducks.

The thickness of the perimysium has an essential effect on the tenderness of the meat. However, the genetic basis underlying perimysial thickness has not been determined. The objective of this study was to explore the quantitative trait loci (QTL) that influence perimysial thickness in an F2 segregating population generated by Mallard × Pekin duck using the genome-wide association study (GWAS) method. Two QTL identified in chromosomes 27 and 13 displayed significant associations with perimysial thickness traits at the genome-wide level. The strongest association was the QTL located in chromosome 27, and this region had an effect on perimysial thickness and contained a promising candidate gene MAGI3 (Membrane-associated guanylate kinase, WW and PDZ domain containing 3). Meanwhile, association analysis showed that the top SNP within the MAGI3 gene was also associated with intramuscular fat content traits, which showed that perimysial thickness was positively correlated with intramuscular fat content. The second strongest association was the QTL region of chromosome 13. SUCLG2 (Succinate-CoA ligase GDP-forming subunit beta) is proximal to the top SNP and stood out as another candidate gene. Furthermore, the Transposase-Accessible Chromatin using Sequencing result showed that some key transcription factors (MYF5, MYOD1, KLF11) related to muscle development or energy metabolism might bind to the open regions of MAGI3 and SUCLG2. By analyzing the expression of different genotypes of the candidate gene, we speculate that different genotypes of MAGI3 may have an effect on breast muscle development, and then affect the thickness of the perimysium. This study maps two major genes of the duck breast muscle perimysial thickness trait, which helps to characterize muscle development and contributes to the genetic improvement of meat yield and quality in livestock.

Effect of riboflavin deficiency on intestinal morphology, jejunum mucosa proteomics, and cecal microbiota of Pekin ducks.

This study was to determine the effects of riboflavin deficiency (RD) on intestinal development, jejunum mucosa proteome, cecal short-chain fatty acids (SCFA) profiling, and cecal microbial diversity and community of starter Pekin ducks. Male white Pekin ducks (1 d old, n = 240) were allocated into 2 groups, with 12 replicates and 10 birds per replicate in each group. For 21 d, all ducks had ad libitum access to either an RD or a riboflavin adequate (control, CON) diet, formulated by supplementing a basal diet with 0 or 10 mg riboflavin per kg of diet, respectively. Compared to the CON group, growth retardation, high mortality, and poor riboflavin status were observed in the RD group. Furthermore, RD reduced the villus height and the ratio of villus height to crypt depth of jejunum and ileum (P < 0.05), indicating morphological alterations of the small intestine. In addition, dietary RD enhanced relative cecum weight and decreased cecal SCFA concentrations (P < 0.05), including propionate, isobutyrate, butyrate, and isovalerate. The jejunum mucosa proteomics showed that 208 proteins were upregulated and 229 proteins were downregulated in the RD group compared to those in the CON group. Among these, RD mainly suppressed intestinal absorption and energy generation processes such as glycolysis and gluconeogenesis, fatty acid beta oxidation, tricarboxylic acid cycle, and oxidative phosphorylation, leading to impaired ATP generation. In addition, RD decreased the community richness and diversity of the bacterial community in the cecum of ducks. Specifically, RD reduced the abundance of butyrate-producing bacteria in the cecum (P < 0.05), such as Eubacterium coprostanoligenes, Prevotella and Faecalibacterium. Dietary RD resulted in growth depression and intestinal hypofunction of Pekin ducks, which could be associated with impaired intestinal absorption and energy generation processes in intestinal mucosa, as well as gut microbiota dysbiosis. These findings contribute to our understanding of the mechanisms of intestinal hypofunction due to RD.

Design and validation of performance-oriented injectable chitosan thermosensitive hydrogels for endoscopic submucosal dissection.

Endoscopic submucosal dissection (ESD) is a challenging procedure. The use of biomaterials to improve the operator's convenience (operating affinity) has received little attention. We prepared two thermosensitive hydrogels, lactobionic acid-modified chitosan/chitosan/ß-glycerophosphate thermosensitive hydrogel (hydrogel 1) and its lyophilized powders (hydrogel 2), characterized their physicochemical properties and evaluated their performance in ESD experiments on large animals, by comparing with the commonly used normal saline (NS) and glycerin fructose (GF). These hydrogels showed good low-temperature fluidity; their viscosities at 4 °C were 92.2 mPa.s and 26.9 mPa.s, respectively. The hydrogels provided significantly better viscoelastic properties than NS and GF. The relaxation moduli of hydrogels were higher than those of NS and GF when the strains were 1 %, 5 %, and 10 %. The hydrogels can be maintained for seven days, even at pH 1, after which they degrade entirely. In pig model experiments, we performed submucosal injection and ESD procedures in the stomach and esophagus. The cushion height produced by the hydrogels was higher than those of NS and GF 30 min after injection. The ESD operation time for hydrogels was significantly shorter. Postoperative wound observation and histological analysis showed that the hydrogels promoted wound healing. The two hydrogels differed in fluidity, viscoelasticity, and other properties, which makes it possible to select the hydrogels according to the size and location of the lesion during ESD operation, and hydrogel 2 may be more suitable for use in lengthier procedures. In general, the hydrogels showed good performance, facilitated the intraoperative operation of ESD, shorten the operation time and promoted wound healing, which is of great significance for reducing the complications and reducing the threshold of ESD operation and further promoting the popularity of ESD.

Genome-wide association study reveals the genetic determinism of serum biochemical indicators in ducks.

BACKGROUND: The serum is rich in nutrients and plays an essential role in electrolyte and acid-base balance, maintaining cellular homeostasis. In addition, serum parameters have been commonly used as essential biomarkers for clinical diagnosis. However, little is known about the genetic mechanism of the serum parameters in ducks. RESULTS: This study measured 18 serum parameters in 320 samples of the F2 segregating population generated by Mallard × Pekin duck. The phenotypic correlations showed a high correlation between LDH, HBDH, AST, and ALT (0.59-0.99), and higher coefficients were also observed among TP, ALB, HDL-C, and CHO (0.46-0.87). And then, we performed the GWAS to reveal the genetic basis of the 18 serum biochemical parameters in ducks. Fourteen candidate protein-coding genes were identified with enzyme traits (AST, ALP, LDH, HBDH), and 3 protein-coding genes were associated with metabolism and protein-related serum parameters (UA, TG). Moreover, the expression levels of the above candidate protein-coding genes in different stages of breast muscle and different tissues were analyzed. Furthermore, the genes located within the high-LD region (r2 > 0.4 and - log10(P) < 4) neighboring the significant locus also remained. Finally, 86 putative protein-coding genes were used for GO and KEGG enrichment analysis, the enzyme-linked receptor protein signaling pathway and ErbB signaling pathway deserve further focus. CONCLUSIONS: The obtained results can contribute to new insights into blood metabolism and provide new genetic biomarkers for application in duck breeding programs.

Riboflavin (Vitamin B2) Deficiency Induces Apoptosis Mediated by Endoplasmic Reticulum Stress and the CHOP Pathway in HepG2 Cells.

Riboflavin is an essential micronutrient and a precursor of flavin mononucleotide and flavin adenine dinucleotide for maintaining cell homeostasis. Riboflavin deficiency (RD) induces cell apoptosis. Endoplasmic reticulum (ER) stress is considered to induce apoptosis, and C/EBP homologous protein (CHOP) is a key pathway involved in this process. However, whether RD-induced apoptosis is mediated by ER stress and the CHOP pathway remains unclear and needs further investigation. Therefore, the current study presents the effect of RD on ER stress and apoptosis in the human hepatoma cell line (HepG2). Firstly, cells were cultured in a RD medium (4.55 nM riboflavin) and a control (CON) medium (1005 nM riboflavin). We conducted an observation of cell microstructure characterization and determining apoptosis. Subsequently, 4-phenyl butyric acid (4-PBA), an ER stress inhibitor, was used in HepG2 cells to investigate the role of ER stress in RD-induced apoptosis. Finally, CHOP siRNA was transfected into HepG2 cells to validate whether RD triggered ER stress-mediated apoptosis by the CHOP pathway. The results show that RD inhibited cell proliferation and caused ER stress, as well as increased the expression of ER stress markers (CHOP, 78 kDa glucose-regulated protein, activating transcription factor 6) (p < 0.05). Furthermore, RD increased the cell apoptosis rate, enhanced the expression of proapoptotic markers (B-cell lymphoma 2-associated X, Caspase 3), and decreased the expression of the antiapoptotic marker (B-cell lymphoma 2) (p < 0.05). The 4-PBA treatment and CHOP knockdown markedly alleviated RD-induced cell apoptosis. These results demonstrate that RD induces cell apoptosis by triggering ER stress and the CHOP pathway.

Integrated liver proteomics and metabolomics identify metabolic pathways affected by pantothenic acid deficiency in Pekin ducks.

Pantothenic acid deficiency (PAD) in animals causes growth depression, fasting hypoglycemia and impaired lipid and glucose metabolism. However, a systematic multi-omics analysis of effects of PAD on hepatic function has apparently not been reported. We investigated liver proteome and metabolome changes induced by PAD to explain its effects on growth and liver metabolic disorders. Pekin ducks (1-d-old, n = 128) were allocated into 2 groups, with 8 replicates and 8 birds per replicate. For 16 d, all ducks had ad libitum access to either a PAD or a pantothenic acid adequate (control, CON) diet, formulated by supplementing a basal diet with 0 or 8 mg pantothenic acid/kg of diet, respectively. Liver enlargement, elevated liver glycogen concentrations and decreased liver concentrations of triglyceride and unsaturated fatty acids were present in the PAD group compared to the CON group. Based on integrated liver proteomics and metabolomics, PAD mainly affected glycogen synthesis and degradation, glycolysis and gluconeogenesis, tricarboxylic acid (TCA) cycle, peroxisome proliferator-activated receptor (PPAR) signaling pathway, fatty acid beta oxidation, and oxidative phosphorylation. Selected proteins were confirmed by Western blotting. Downregulation of proteins and metabolites involved in glycogen synthesis and degradation, glycolysis and gluconeogenesis implied that these processes were impaired in PAD ducks, which could have contributed to fasting hypoglycemia, liver glycogen storage, insufficient ATP production, and growth retardation. In contrast, PAD also upregulated proteins and metabolites involved in fatty acid beta oxidation, the TCA cycle, and oxidative phosphorylation processes in the liver; presumably compensatory responses to produce ATP. We inferred that PAD decreased liver triglyceride and unsaturated fatty acids by activating fatty acid beta oxidation and impairing unsaturated fatty acid synthesis. These findings contributed to our understanding of the mechanisms of PAD-induced changes in hepatic metabolism.

Dietary methionine deficiency stunts growth and increases fat deposition via suppression of fatty acids transportation and hepatic catabolism in Pekin ducks.

BACKGROUND: Although methionine (Met), the first-limiting dietary amino acid, has crucial roles in growth and regulation of lipid metabolism in ducks, mechanisms underlying are not well understood. Therefore, the objective was to use dietary Met deficiency to investigate the involvement of Met in lipid metabolism and fat accumulation of Pekin ducks. METHODS: A total of 150 male Pekin ducks (15-d-old, 558.5 ± 4.4 g) were allocated into 5 groups (6 replicates with 5 birds each) and fed corn and soybean meal-based diets containing 0.28%, 0.35%, 0.43%, 0.50%, and 0.58% Met, respectively, for 4 weeks. Met-deficient (Met-D, 0.28% Met) and Met-adequate (Met-A, 0.43% Met) groups were selected for subsequent molecular studies. Serum, liver, and abdominal fat samples were collected to assess the genes and proteins involved in lipid metabolism of Pekin ducks and hepatocytes were cultured in vivo for verification. RESULTS: Dietary Met deficiency caused growth depression and excess fat deposition that were ameliorated by feeding diets with adequate Met. Serum triglyceride and non-esterified fatty acid concentrations increased (P < 0.05), whereas serum concentrations of total cholesterol, low density lipoprotein cholesterol, total protein, and albumin decreased (P < 0.05) in Met-D ducks compared to those in Met-A ducks. Based on hepatic proteomics analyses, dietary Met deficiency suppressed expression of key proteins related to fatty acid transport, fatty acid oxidation, tricarboxylic acid cycle, glycolysis/gluconeogenesis, ketogenesis, and electron transport chain; selected key proteins had similar expression patterns verified by qRT-PCR and Western blotting, which indicated these processes were likely impaired. In vitro verification with hepatocyte models confirmed albumin expression was diminished by Met deficiency. Additionally, in abdominal fat, dietary Met deficiency increased adipocyte diameter and area (P < 0.05), and down-regulated (P < 0.05) of lipolytic genes and proteins, suggesting Met deficiency may suppress lipolysis in adipocyte. CONCLUSION: Taken together, these data demonstrated that dietary Met deficiency in Pekin ducks resulted in stunted growth and excess fat deposition, which may be related to suppression of fatty acids transportation and hepatic catabolism.

Genome-wide association analysis reveal the genetic reasons affect melanin spot accumulation in beak skin of ducks.

BACKGROUND: Skin pigmentation is a broadly appearing phenomenon of most animals and humans in nature. Here we used a bird model to investigate why melanin spot deposits on the skin. RESULTS: Our result showed that growth age and the sunlight might induce melanin deposition in bird beak skin which was determined by genetic factors. GWAS helped us to identify two major loci affecting melanin deposition, located on chromosomes 13 and 25, respectively. The fine mapping works narrowed the candidate regions to 0.98 Mb and 1.0 Mb on chromosomes 13 and 25. The MITF and POU2F3 may be the causative genes and synergistically affect melanin deposition during duck beak skin. Furthermore, our data strongly demonstrated that the pathway of melanin metabolism contributes to melanin deposition on the skin. CONCLUSIONS: We demonstrated that age and sunlight induce melanin deposition in bird beak skin, while heredity is fundamental. The MITF and POU2F3 likely played a synergistic effect on the regulation of melanin synthesis, and their mutations contribute to phenotypic differences in beak melanin deposition among individuals. It is pointed out that melanin deposition in the skin is related to the pathway of melanin metabolism, which provided insights into the molecular regulatory mechanisms and the genetic improvement of the melanin deposition in duck beak.

Genome-wide association and selective sweep analyses reveal genetic loci for FCR of egg production traits in ducks.

BACKGROUND: As a major economic trait in poultry, egg production efficiency attracts widespread interest in breeding and production. However, limited information is available about the underlying genetic architecture of egg production traits in ducks. In this paper, we analyzed six egg production-related traits in 352 F2 ducks derived from reciprocal crosses between mallard and Pekin ducks. RESULTS: Feed conversation ratio (FCR) was positively correlated with feed intake but negatively correlated with egg-related traits, including egg weight and egg production, both phenotypically and genetically. Estimates of pedigree-based heritability were higher than 0.2 for all traits investigated, except hip-width. Based on whole-genome sequencing data, we conducted genome-wide association studies to identify genomic regions associated with these traits. In total, 11 genomic regions were associated with FCR. No genomic regions were identified as significantly associated with hip-width, total feed intake, average daily feed intake, and total egg production. Analysis of selective sweeps between mallard and Pekin ducks confirmed three of these genomic regions on chromosomes 13, 3 and 6. Within these three regions, variants in candidate genes that were in linkage disequilibrium with the GWAS leader single nucleotide polymorphisms (SNPs) (Chr13:2,196,728, P = 7.05 × 10-14; Chr3:76,991,524, P = 1.06 × 10-12; Chr6:20,356,803, P = 1.14 × 10-10) were detected. Thus, we identified 31 potential candidate genes associated with FCR, among which the strongest candidates are those that are highly expressed in tissues involved in reproduction and nervous system functions of ducks: CNTN4, CRBR, GPR63, KLHL32, FHL5, TRNT1, MANEA, NDUFAF4, and SCD. CONCLUSIONS: For the first time, we report the identification of genomic regions that are associated with FCR in ducks and our results illustrate the genomic changes that occurred during their domestication and are involved in egg production efficiency.