Duck Egg Production Research Articles

Lipidomics combined with random forest machine learning algorithms to reveal freshness markers for duck eggs during storage in different rearing systems

The differences in lipids in duck eggs between the 2 rearing systems during storage have not been fully studied. Herein, we propose untargeted lipidomics combined with a random forest (RF) algorithm to identify potential marker lipids based on ultra-performance liquid chromatography‒mass spectrometry (UPLPC-MS/MS). A total of 106 and 16 differential lipids (DL) were screened in egg yolk and white, respectively. In yolk, metabolic pathway analysis of DLs revealed that glycerophospholipid metabolism and sphingolipid metabolism were the key metabolic pathways in the traditional free-range system (TFS) during storage, glycosylphosphatidylinositol-anchored biosynthesis and glyceride metabolism were the key pathways in the floor-rearing system (FRS). In egg white, the key pathway in both systems is the biosynthesis of unsaturated fatty acids. Combined with RF algorithm, 12 marker lipids were screened during storage. Therefore, this study elucidates the changes in lipids in duck eggs during storage in 2 rearing systems and provides new ideas for screening marker lipids during storage. This approach is highly important for evaluating the quality of egg and egg products and provides guidance for duck egg production.

Genome-wide association study identified candidate genes for egg production traits in the Longyan Shan-ma duck

Egg production is an important economic trait in layer ducks and understanding the genetics basis is important for their breeding. In this study, a genome-wide association study (GWAS) for egg production traits in 303 female Longyan Shan-ma ducks was performed based on a genotyping-by-sequencing strategy. Sixty-two single nucleotide polymorphisms (SNPs) associated with egg weight traits were identified (P < 9.48 × 10-5), including 8 SNPs at 5% linkage disequilibrium (LD)-based Bonferroni-corrected genome-wide significance level (P < 4.74 × 10-6). One hundred and nineteen SNPs were associated with egg number traits (P < 9.48 × 10-5), including 13 SNPs with 5% LD-based Bonferroni-corrected genome-wide significance (P < 4.74 × 10-6). These SNPs annotated 146 target genes which contained known candidate genes for egg production traits, such as prolactin and prolactin releasing hormone receptor. This study identified that these associated genes were significantly enriched in egg production-related pathways (P < 0.05), such as the oxytocin signaling, MAPK signaling, and calcium signaling pathways. It was notable that 18 genes were differentially expressed in ovarian tissues between higher and lower egg production in Shan-ma ducks. The identified potential candidate genes and pathways provide insight into the genetic basis underlying the egg production trait of layer ducks.

Ammonia negatively impacted egg production and altered the diversity of microbial communities in cage-reared Muscovy ducks

The aim of this study was to examine the effects of NH3 variations across different positions within a cage-reared duck house on the egg production performance and fecal microbiome in Muscovy ducks. Totals of 3,168 female Muscovy ducks (180 ± 2 d) were randomly assigned to 1,056 cages. From d 293 to 300, the egg production rate and levels of NH3, H2S, CO2, temperature, humidity, light intensity, and dust particles were recorded. Two spatial distribution-based experimental classification methods were applied, one grouping ducks into Front, Middle, and End categories, and the other into First, Second, and Third layers. On d 300, serum and feces samples were collected for further analysis. The result showed that both the egg production rate and serum PROG level in the Front were higher than End (P < 0.05). However, no significant differences were found among the First, Second, and Third groups. Among the environmental factors, ammonia (NH3) is a major harmful gas in cage-reared duck houses, with observed concentrations showing a gradient from lower levels in the Front group to higher levels in the Middle group (P < 0.05), and even higher levels in the End group (P < 0.05). Gene sequencing of the 16S rRNA gene revealed a higher relative abundance of Firmicutes in both the Front and Middle groups compared to the End group (P < 0.05). Specifically, within the Firmicutes phylum, the relative abundance of Lactobacillus and Romboutsia was notably higher in the Front group compared to both the Middle and End groups (P < 0.05). What's more, the abundance of Lactobacillus had a negative correlation with NH3 concentration and positive correlation with egg production rate. In conclusion, NH3 concentrations showed variations across different areas of the cage-reared duck house, with higher levels detected at the rear. The elevated NH3 level was identified as the main factor negatively impacting egg production in Muscovy ducks and contributing to a decline in the abundance of Firmicutes, specifically Lactobacillus.

Cell Heterogeneity Analysis Revealed the Key Role of Fibroblasts in the Magnum Regression of Ducks.

Duck egg production, like that of laying hens, follows a typical low-peak-low cycle, reflecting the dynamics of the reproductive system. Post-peak, some ducks undergo a cessation of egg laying, indicative of a regression process in the oviduct. Notably, the magnum, being the longest segment of the oviduct, plays a crucial role in protein secretion. Despite its significance, few studies have investigated the molecular mechanisms underlying oviduct regression in ducks that have ceased laying eggs. In this study, we conducted single-cell transcriptome sequencing on the magnum tissue of Shaoxing ducks at 467 days of age, utilizing the 10× Genomics platform. This approach allowed us to generate a detailed magnum transcriptome map of both egg-laying and ceased-laying ducks. We collected transcriptome data from 13,708 individual cells, which were then subjected to computational analysis, resulting in the identification of 27 distinct cell clusters. Marker genes were subsequently employed to categorize these clusters into specific cell types. Our analysis revealed notable heterogeneity in magnum cells between the egg-laying and ceased-laying ducks, primarily characterized by variations in cells involved in protein secretion and extracellular matrix (ECM)-producing fibroblasts. Specifically, cells engaged in protein secretion were predominantly observed in the egg-laying ducks, indicative of their role in functional albumen deposition within the magnum, a phenomenon not observed in the ceased-laying ducks. Moreover, the proportion of THY1+ cells within the ECM-producing fibroblasts was found to be significantly higher in the egg-laying ducks (59%) compared to the ceased-laying ducks (24%). Similarly, TIMP4+ fibroblasts constituted a greater proportion of the ECM-producing fibroblasts in the egg-laying ducks (83%) compared to the ceased-laying ducks (58%). These findings suggest a potential correlation between the expression of THY1 and TIMP4 in ECM-producing fibroblasts and oviduct activity during functional reproduction. Our study provides valuable single-cell insights that warrant further investigation into the biological implications of fibroblast subsets in the degeneration of the reproductive tract. Moreover, these insights hold promise for enhancing the production efficiency of laying ducks.

Whole-Transcriptome Sequencing of Ovary Reveals the ceRNA Regulation Network in Egg Production of Gaoyou Duck.

To investigate the regulatory mechanism of the competing endogenous RNAs (ceRNAs) on the egg performance of Gaoyou ducks, full transcriptome sequencing was performed to analyze the ovarian tissues in Gaoyou ducks. The ducks were categorized into high- and low-yield groups based on the individual in-cage egg production records and the hematoxylin-eosin (HE) staining results. The differentially expressed genes (DEGs), long non-coding RNAs (lncRNAs), and circular RNAs (circRNAs) were further processed by GO (gene ontology) and KEGG (Kyoto Encyclopedia of Genes and Genomes) analyses. In total, 72 DEmRNAs; 23 DElncRNAs; 4 DEcircRNAs; and 5 signaling pathways, including the ovarian steroidogenesis, PI3K-Akt, hedgehog, tryptophan metabolism, and oocyte meiosis signaling pathways, were significantly enriched. These results suggest that they could be associated with the Gaoyou duck's ovarian function and affect the total egg production or double-yolked egg production. Furthermore, a coregulation network based on the related candidate ceRNAs across the high- and low-yield egg production groups was constructed. Our findings provide new insights into the mechanisms underlying the molecular regulation of related circRNA/lncRNA-miRNA-mRNA in the egg production and double-yolked egg traits of Gaoyou ducks.

Role of Cherry Valley duck IRF1 mediated signal pathway in host anti-duck Tembusu virus

China is the country with the largest amount of duck breeding as well as duck meat and egg production. In recent years, the emergence and spread of duck Tembusu virus (DTMUV) has become one of the important factors in reducing the amount of duck slaughter, which seriously endangers the duck breeding industry in our country. In-depth research on the mechanism of duck innate immunity facilitates the exploration of new models for the treatment of DTMUV infection. IRF1 can induce the expression of many antiviral immune factors in the animal organism and play an important role in the innate immune response. In this study, we used interfering RNA to knock down the IRF1 gene in DEF cells and then the cells were infected with DTMUV. We found that knockdown of IRF1 promoted DTMUV replication at an early stage and caused downregulation of the expression of several major pattern recognition receptors (PRRs), interleukins (IL), interferons (IFN), antiviral proteins, and MHC molecules by assay, showing that the duIRF1-mediated signaling pathway plays an extremely important role in DTMUV-induced host innate immunity. In addition, we constructed the recombinant expression plasmid pET32a(+)-duIRF1-His, and finally prepared the polyclonal antibody of duIRF1 with good specificity, hoping to provide a detection means for research on the mechanism of IRF1 in innate immunity in our laboratory and in this field.

MENGEMBANGKAN KUALITAS TELUR ITIK ASIN: PELATIHAN PROSES FERMENTASI TELUR ITIK ASIN DENGAN STARTER BAKTERI ASAM LAKTAT M-BIO

The conventional production of salted duck eggs has limitations in producing high-quality products, and the traditional process involves several lengthy stages. This community service initiative focuses on socializing and providing training on salted duck egg production using the fermentation method with a biosimultaneous approach from M-Bio, which contains essential lactic acid bacteria. The advantage of producing salted duck eggs using the fermentation method with lactic acid bacteria starter lies in its ability to yield eggs with improved quality in both the egg white and yolk. This community service utilized socialization and training methods, with collaboration partners being Ponpes Murottalul Qur’an Al-Mu’minun and the Family Welfare Empowerment Society (PKK). The location of the community service initiative was in the Cilembang Subdistrict, Cihideung District, Tasikmalaya City, West Java. Thirty participants engaged in the training on salted duck egg production. The community displayed high enthusiasm and curiosity, likely due to their exposure to new information about salted duck egg production using the fermentation method. The outcomes of this community service include the improved skills of participants in salted duck egg production and the economic potential of the resulting products. Product evaluation and ongoing monitoring are necessary to ensure product quality and the sustained positive impact on the community.

Short Communication: Polymorphism of collagen type X (COLX) gene and their association with egg production traits and egg weight in Alabio and Mojosari ducks

Abstract. Kumalawati DS, Maharani D, Sari APZNL, Pratomo GH, Sasongko H, Fathoni A, Susanti T. 2023. Short Communication: Polymorphism of collagen type X (COLX) gene and their association with egg production traits and egg weight in Alabio and Mojosari ducks. Biodiversitas 24: 1518-1523. Type X collagen (COLX) is non-fibrillar collagen expressed in the white isthmus of the avian oviduct and plays a role in egg formation. This study aimed to identify COLX gene polymorphism and its association with egg production and egg weight in Alabio (Anas platyrhynchos Borneo) and Mojosari ducks (Anas platyrhynchos Javanicus). Blood samples of 100 female ducks were collected, and their deoxyribonucleic acid (DNA) was extracted. In addition, a 220 bp fragment of COLX gene was amplified using the polymerase chain reaction (PCR) method and sequenced for single nucleotide polymorphism (SNP) identification and genotyping. Data analysis was performed to calculate genotype and allele frequencies, and an independent sample t-test was used to examine the association between genotype and egg production and egg weight of each individual. Three genotypes (CC, TT, and CT) of SNP g.74C/T were detected in both breeds. Allele C (0.77) was dominant in Alabio population; otherwise, allele T (0.81) dominated Mojosari population. The frequency of CC (0.59) was highest in Alabio ducks, followed by CT (0.37) and TT (0.04), while TT (0.65) was highest in Mojosari ducks, followed by CT (0.33) and CC (0.02). Meanwhile, association analysis showed that ducks with CC genotype had significantly higher egg production at 28 and 34 weeks in Alabio than those with CT genotype (p&lt;0.05). These results indicate that COLX is an effective genetic marker for a breeding program to increase egg production in Alabio ducks.

Whole-genome sequencing identifies potential candidate genes for egg production traits in laying ducks (Anas platyrhynchos)

Egg production traits are economically important in laying ducks. Genetic molecular mechanisms and candidate genes underlying these traits remain unclear. In this study, whole genome variants were identified through whole-genome resequencing using three high-egg producing (HEN) and three low-egg producing (LEN) laying ducks. The gene ontology (GO) terms and Kyoto Encyclopedia of Genes and Genome (KEGG) pathways for the genes of common differential variants between HEN and LEN ducks were determined. Frizzled class receptor 6 (FZD6) was further genotyped using the Sequenom MassARRAY iPLEX platform. The association of FZD6 gene polymorphisms with 73 egg production and weight traits in 329 female ducks were estimated. A total of 65,535 single nucleotide polymorphisms (SNPs) and 4,702 indels were identified across the genome. Fourteen GO terms and 14 KEGG pathways were determined for the genes of common differential variants, including MAPK signaling, Wnt signaling, melanogenesis and calcium signaling pathways, which are key functional pathways for poultry egg production reported in previous reports. Further analysis showed that 27 SNPs of FZD6 were associated with three early egg production of duck and egg weight traits, including egg production at 17 weeks (EP17), 18 weeks (EP18) and 19 weeks (EP19) and egg weight at 59 weeks (EW59). The FZD6 should be considered a novel candidate gene for egg production traits in laying ducks.

Transcriptomic analysis of the thyroid and ovarian stroma reveals key pathways and potential candidate genes associated with egg production in ducks

The importance of thyroid-related genes has been repeatedly mentioned in the transcriptome studies of poultry with different laying performance, yet there are few systematic studies to unravel the regulatory mechanisms of the thyroid-ovary axis in the poultry egg production process. In this study, we compared the transcriptome profiles in the thyroid and ovarian stroma between high egg production (GP) and low egg production (DP) ducks, and then revealed the pathways and candidate genes involved in the process. We identified 1,114 and 733 differentially expressed genes (DEGs) in the thyroid and ovarian stroma, separately. The Gene Ontology (GO) analysis showed that a total of 504 and 189 GO terms were identified in the thyroid and ovarian stroma (P < 0.05). Three common GO terms were identified from the top 5 GO terms with the highest significant level in two tissues, including extracellular space, calcium ion binding, and integral component of plasma membrane. The enrichment analysis of the Kyoto Encyclopedia of Genes and Genomes (KEGG) showed that 15 and 14 KEGG pathways were significantly (P < 0.05) enriched in the thyroid and ovarian stroma, respectively. And, there were 8 common pathways, including neuroactive ligand-receptor interaction, calcium signaling pathway, ECM-receptor interaction, PPAR signaling pathway, melanogenesis, wnt signaling pathway, vascular smooth muscle contraction, and cytokine-cytokine receptor interaction. Notably, the neuroactive ligand-receptor interaction pathway was the most significantly enriched by the DEGs both in the thyroid and ovarian stroma. The interaction among DEGs enriched in the neuroactive ligand-receptor interaction and ECM-receptor interaction suggested that the thyroid may regulate ovarian development by these genes. Through integrated analysis of the protein-protein interaction (PPI) network and KEGG pathway maps, 9 key DEGs (PTH, THBS2, THBS4, CD36, ADIPOQ, ACSL6, PRKAA2, CRH, and PCK1) were identified, which could play crucial roles in the thyroid to regulate ovarian function and then affect egg-laying performance between GP and DP. This study serves as a basis to explore the molecular mechanism of the thyroid affecting ovarian function and egg production in female ducks and may help to identify molecular markers that can be used for duck genetic selection.

Effect of replacing wheat with broken rice on nutrients metabolisability, egg production and quality in White Pekin ducks

A study was conducted in the tropical coastal region of Odisha in 2019 to find out the effect of replacing wheat with broken rice (BR) on nutrients metabolisability, egg production and quality in White Pekin ducks. White Pekin ducks (45, 165 days) were divided into three groups with three replicates in each group and each replicate had five ducks. Three experimental diets without (BR-0) and with BR, replacing 50 (BR-50) and 100 (BR-100), per cent wheat were prepared. The above diets were offered randomly to the groups till 40 weeks followed by conduction of a metabolic trial. The dry matter intake (g/d) was similar among the groups. The metabolisability percentage of dry matter, organic matter, crude protein, ether extract and crude fibre in BR-0 and BR-50 were similar and higher than BR-100. There was no significant difference in N balance (g/d) among the groups. The total egg production, duck day egg production percentage and feed conversion ratio were similar among the groups. The external and internal egg quality parameters were similar among the groups as well. It was concluded that wheat can be replaced with broken rice at 50% level in the diets of White Pekin ducks during first phase of laying under intensive rearing system with increase in the metabolisability of the nutrients of the feed without affecting the performance.

Research Note: Association of single nucleotide polymorphism of AKT3 with egg production traits in White Muscovy ducks (Cairina moschata)

Prior studies on transcriptomes of hypothalamus and ovary revealed that AKT3 is one of the candidate genes that might affect egg production in White Muscovy ducks. The role of AKT3 in the uterus during reproductive processes cannot be overemphasized. However, functional role of this gene in the tissues and on egg production traits of Muscovy ducks remains unknown. To identify the relationship between AKT3 and egg production traits in ducks, relative expression profile was first examined prior to identifying the variants within AKT3 that may underscore egg production traits [age at first egg (AFE), number of eggs at 300 d (N300D), and number of eggs at 59 wk (N59W)] in 549 ducks. The mRNA expression of AKT3 gene in high producing (HP) ducks was significantly higher than low producing (LP) ducks in the ovary, oviduct, and hypothalamus (P < 0.05 or 0.001). Three variants in AKT3 (C-3631A, C-3766T, and C-3953T) and high linkage block between C-3766T and C-3953T which are significantly (P < 0.05) associated with N300D and N59W were discovered. This study elucidates novel knowledge on the molecular mechanism of AKT3 that might be regulating egg production traits in Muscovy ducks.

Egg Production, Egg Quality, and Fatty Acid Profile of Indonesian Local Ducks Fed with Turmeric, Curcuma, and Probiotic Supplementation

Indonesian local ducks are commonly raised for egg production purposes. However, the performances of these ducks are still variable and must be improved. This study investigated the effects of turmeric, curcuma, and probiotic supplementations on the egg production and quality of Indonesian local ducks, emphasizing the eggs’ fatty acid profile. Two hundred female local ducks aged 16 weeks were randomly allotted to four dietary treatments with five replicates of 10 birds. The ducks were fed a corn and rice bran-based diet containing different supplements, i.e., a diet without supplementation as the control diet, a diet supplemented with turmeric at the level of 4%, a diet supplemented with curcuma at the level of 4%, and a diet supplemented with starbio probiotics at the level of 2%. The measured data were analyzed using analysis of variance using the 13 Systat program and continued with Duncan’s Multiple Range Test. Turmeric supplementation increased egg production compared with the control, and the duck fed probiotics consumed more feed than the control. Curcuma supplementation generated the lowest feed consumption, egg production, and physical egg quality than the other treatments (p<0.05). The probiotics supplementation enhanced the blood high-density lipoprotein concentration (p<0.05). Turmeric, curcuma, and probiotics supplementations generate variable responses in egg production and egg quality, including the fatty acid profile in the eggs. Turmeric and probiotics supplementations positively impact egg production, egg quality, or unsaturated fatty acid profile in the egg. However, curcuma supplementation decreased egg production and egg quality of local ducks. Furthermore, the fatty acid profile was not influenced by these supplements. It is concluded that supplementation of turmeric at the level of 4% and probiotics at the level of 2% in the diet can increase egg production and egg quality of local duck.

Comparative transcriptome analysis of Indian domestic duck reveals candidate genes associated with egg production

Egg production is an important economic trait and a key indicator of reproductive performance in ducks. Egg production is regulated by several factors including genes. However the genes involved in egg production in duck remain unclear. In this study, we compared the ovarian transcriptome of high egg laying (HEL) and low egg laying (LEL) ducks using RNA-Seq to identify the genes involved in egg production. The HEL ducks laid on average 433 eggs while the LEL ducks laid 221 eggs over 93 weeks. A total of 489 genes were found to be significantly differentially expressed out of which 310 and 179 genes were up and downregulated, respectively, in the HEL group. Thirty-eight differentially expressed genes (DEGs), including LHX9, GRIA1, DBH, SYCP2L, HSD17B2, PAR6, CAPRIN2, STC2, and RAB27B were found to be potentially related to egg production and folliculogenesis. Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis suggested that DEGs were enriched for functions related to glutamate receptor activity, serine-type endopeptidase activity, immune function, progesterone mediated oocyte maturation and MAPK signaling. Protein–protein interaction network analysis (PPI) showed strong interaction between 32 DEGs in two distinct clusters. Together, these findings suggest a mix of genetic and immunological factors affect egg production, and highlights candidate genes and pathways, that provides an understanding of the molecular mechanisms regulating egg production in ducks and in birds more broadly.

Study for Some Body Weight and Egg Traits in Domyati and Khaki-Campbell Ducks

The duck industry makes an important contribution to the availability of animal protein sources in Egypt, little known about the genetic parameters, particularly the heritability and genetic correlations of body weight and egg production in ducks. Body weight is the most essential feature for genetic improvement due to its ease of selection, high heredity, and large impact on meat production costs. The target of this study was to evaluate and explain genetic parameters such as the heritability, the genetic and phenotypic correlations, and sire breeding value in Domyati (local) and Khaki-Campbell (foreign) ducks in order to improve body weight and egg traits. A total of 160 (80 Domyati and 80 Khaki-Campbell ducks utilized to measure body weight at 16 and 20 weeks g), as well as 7000 eggs (2500 Domyati and 4500 Khaki-Campbell) to measure egg traits (the egg number, egg weight, and egg mass are all measured throughout the first 90 days of laying). In Domyati and Khaki-Campbell ducks, the heritability estimated for body weight was moderate to high, ranged from 0.35 to 0.40, and 0.21 to 0.30 for egg production. The genetic correlations among body weight and egg traits were all positive and had high values, also among BW16 and BW20 were stronger (0.90); (0.99). So the genetic improvement in BW16 could be followed by an increase in BW20 weeks. It concluded that, the relatively high value of genetic heritability for body weights and egg traits in Domyati and Khaki-Campbell ducks, indicates that it is possible to genetically increase body weight and egg traits through selection and subsequently inbreeding to divide the herd into groups that are selected among themselves to keep their sons.

Growth, Egg Production, and Phenotypic Characteristics of the Commercial Hybrid Egg-type Philippine Mallard Duck (IP Kayumanggi) under Intensive Management System

Five separate studies were conducted to determine the growth and egg production performance of Itik Pinas (IP) Kayumanggi, a new commercial hybrid egg-type mallard duck in the Philippines under an intensive management system. Results showed that the IP Kayumanggi produced by crossing male IP Khaki and female IP Itim as parents showed significant sexual dimorphism in down feather patterns. The male and female ducklings have 98% black and 99% brown down feathers upon hatch, respectively. In addition, the female ducklings have significantly higher body weight from Weeks 0–4, whereas males were heavier from Weeks 10–18. Cumulative feed consumption was 10.72 kg from brooding (Weeks 1–4) to growing (Weeks 5–16). Daily feed consumption per bird was 124 g during the pre-laying (Weeks 17–18) and laying (Weeks 19–50) periods. Phenotypic characterization revealed that males have predominantly dusky black plumage, green bill, and brown shank, whereas females have mallard-type brown plumage, black bill, and orange shank. The males have significantly higher values for all the body measurements. The average age at first lay was 18 wk, and it reached 80% egg production at 26 wk of age. Average egg weight was 67 g. The average fertility, hatchability, and hatch of fertile were 89, 55, and 62%, respectively. This study provided baseline information on the productive and reproductive performance of IP Kayumanggi.

Comparative liver transcriptome analysis of duck reveals potential genes associated with egg production.

Molecular studies on egg production in ducks were mostly focused on brain and ovaries as they are directly involved in egg production. Liver plays a vital role in cellular lipid metabolism. It also plays a decisive role in reproductive organ development, including yolk generation in laying ducks at sexual maturity. However, the precise molecular mechanism involved in the liver-blood-ovary axis in ducks remains elusive. In this study, we analysed the liver transcriptome of laying (LA), immature (IM) and broody (BR) ducks using RNA sequencing to understand the role of genes expressed in the liver. The comparative transcriptome analysis revealed 82 DEGs between LA and IM ducks, 47 DEGs between LA and BR ducks and 51 DEGs between IM and BR ducks. GO analysis of DEGs, showed that DEGs were mainly involved in cellular anatomical entity, intracellular, metabolic process, and binding. Furthermore, pathway analysis indicated the important role of Wnt signaling pathway in egg formation and embryo development. Our study showed several candidate genes including vitellogenin-1, vitellogenin-2, riboflavin binding protein, G protein subunit gamma 4, and fatty acid binding protein 3 that are potentially related to egg production in ducks. The study provides valuable information on the genes responsible for egg production and thus, pave the way for further investigation on the molecular mechanisms of egg production in duck.

Transcriptomic analyses of the HPG axis-related tissues reveals potential candidate genes and regulatory pathways associated with egg production in ducks

BackgroundEgg production is one of the most important economic traits in the poultry industry. The hypothalamic-pituitary–gonadal (HPG) axis plays an essential role in regulating reproductive activities. However, the key genes and regulatory pathways within the HPG axis dominating egg production performance remain largely unknown in ducks.ResultsIn this study, we compared the transcriptomic profiles of the HPG-related tissues between ducks with high egg production (HEP) and low egg production (LEP) to reveal candidate genes and regulatory pathways dominating egg production. We identified 543, 759, 670, and 181 differentially expressed genes (DEGs) in the hypothalamus, pituitary, ovary stroma, and F5 follicle membrane, respectively. Gene Ontology (GO) analysis revealed that DEGs from four HPG axis-related tissues were enriched in the "cellular component" category. Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis indicated that the neuroactive ligand-receptor interaction pathway was significantly enriched based on DEGs commonly identified in all four HPG axis-related tissues. Gene expression profiles and Protein–Protein Interaction (PPI) network were performed to show the regulatory relationships of the DEGs identified. Five DEGs encoding secreted proteins in the hypothalamus and pituitary have interaction with DEGs encoding targeted proteins in the ovary stroma and F5 follicle membrane, implying that they were these DEGs might play similar roles in the regulation of egg production.ConclusionsOur results revealed that neuroactive ligand-receptor interaction pathway and five key genes(VEGFC, SPARC, BMP2, THBS1, and ADAMTS15) were identified as the key signaling pathways and candidate genes within the HPG axis responsible for different egg production performance between HEP and LEP. This is the first study comparing the transcriptomic profiles of all HPG axis-related tissues in HEP and LEP using RNA-seq in ducks to the best of our knowledge. These data are helpful to enrich our understanding of the classical HPG axis regulating the egg production performance and identify candidate genes that can be used for genetic selection in ducks.

Production performance of Alabio ducks (Anas platyrhynchos Borneo) under different levels of drinking water salinity.

Objective:To examine the effects of the salinity level of drinking water on the egg production and quality of Alabio ducks.Materials and Methods:A total of 60 female Alabio ducks, aged 6 months, were subjected to this study. All ducks were kept in stage-type cages (1 m length × 1 m width × 0.5 m height), where each cage was inhabited by 4 ducks for 56 days of experimentation. All ducks were offered a mixed ration ad libitum for laying ducks, according to the nutritional requirements for egg-type ducks. The treatment in this study was drinking water with five stratified salinity levels, namely P0 = freshwater (0% salinity); P1 = water with a salinity of 0.75 practical salinity unit (PSU) (equal to 0.75 g NaCl/l); P2 = water with a salinity of 1.5 PSU (1.5 gm/l); P3 = water with a salinity of 2.5 PSU (2.5 gm/l); and P4 = water with a salinity of 3 PSU (3.0 gm/l). Observations were made on water intake, feed intake, egg production, and egg quality (egg weight, egg shape index density, shell proportion, shell thickness, yolk index, albumen index, and Haugh unit).Results:The results showed that the difference in salinity levels in drinking water from 0.75 PSU to 3 PSU did not affect water intake, feed intake, egg production, or egg quality of Alabio ducks for the first 56 days of the laying period (p > 0.05).Conclusions:It was concluded that Alabio ducks have a good tolerance for drinking water salinity of up to 3 PSU, or equal to 3 gm/l NaCl.

Productivity of germinative duck chimaeras and their descendants

The relevance of the study is conditioned upon the necessity to explore the possible influence of chimerisation on the productivity of germinative duck chimaeras and their descendants. To obtain duck chimaeras, the method described by Aige-Gil &amp; Simkiss and Tagirov was applied. Shanma duck embryos were used as recipients and Shaoxin duck embryos homozygous for the plumage colour gene (wild type) were used as donors. To evaluate the egg production of germinative chimaeras of ducks, the analysis of experimental animals and their control counterparts was performed. Analysis of the age of sexual maturation (laying the first egg) indicates that the chimaeras matured later. While in the control group the average age of puberty was 139±9 days, in the chimaera group it was 148±13 days. Thus, it can be concluded that in this experiment chimaeras matured later than control animals, which may be related to the effect of busulfan during the sterilisation of recipient embryos. The average live weight of ducks in the control group was lower, and the group itself was more united. Thus, in control ducks, the weight was 1422.40±57.00 g, and in chimaeras – 1608.80±94.76 g. The advantage of chimaeras over the control group in terms of live weight may be related to the fact that the control group consisted of recipients of the Shanma breed. Egg production of ducks for the entire research period was 87.5±0.05% (control) and 79.5±0.12% (busulfan). The weight of eggs in ducks of two groups for the entire period was: 70.62±0.199 g (control) and 71.15±0.157 g. Morphometric parameters of eggs of the researched groups of ducks: average values of egg length – 6.056±0.0564 cm (control) and 6.269±0.1341 cm (busulfan); egg width – 4.520± 0.0053 cm (control) and 4.529±0.004 cm (busulfan). There were no statistical intergroup differences in the morphometric parameters of the eggs of the research groups. Analysis of the productivity of daughters of germinative duck chimaeras demonstrates that, in general, the chimerisation of parents did not affect the productivity of their daughters. The analysis of the productivity of the group of daughters obtained from chimeric animals demonstrates that, by most indicators, this group occupies an intermediate place between the groups whose breeds served as donors and recipients. The method author of the research uses to obtain chimaeras is of practical value for the conservation of genetic resources