domestica, Anatidae (Linnaeus, 1758) in different two age stages (post-hatching [P2] and adult female) captured from Egypt

The domestic duck is classified as a specialist filter-feeder bird living in the water. These birds also use grazing and pecking as terrestrial feeding methods. The tongues of domestic ducks, similar to those of other Anseriformes, exhibit numerous types and shapes of mechanical papillae that serve a number of purposes when collecting food. The current study attempts to describe the morphological characteristics of the tongue as well as the mechanical papillae's development. In addition, the study aims to determine whether the papillae observed post-hatching (P2) exhibit similar morphology to those found in adult female avian species, as well as to investigate the readiness of the tongue to fulfill its feeding function following hatching. The comprehensive examination of lingual mucosa is examined about the structural modifications necessary for this variety of feeding activities. In this study, the tongues of nine young (P2) and adult female were used. The tongue had three distinct parts: the apex, which had a lingual nail on its ventral surface; the body, which exhibits numerous small and large conical papillae on its lateral sides and a lingual prominence in the caudal region; and the root, which is covered with numerous conical papillae of varying sizes. Conical, filiform, and hair-like mechanical papillae, the three types of food filtration apparatus, are present in both stages. The intraoral transfer involves several structures, including the median groove, lingual combs, and the rostral border of the lingual prominence. The rostral border of the lingual prominence is characterized by distinct rows of conical papillae. The histological analysis demonstrated the presence of both keratinized and nonkeratinized epithelium on different tongue regions. The lingual salivary glands in the rostral and caudal lingual salivary glands exhibit a pronounced periodic acid-Schiff-positive reaction. Additionally, the yellow adipose tissue and sensory receptors, namely the Grandry and Herbst corpuscles, which collectively form the bill-tongue organ that monitors the movement of food. These results conclude the presence of microstructural species-specific alterations in specific tongue areas of domestic ducks' lingual mucosa. These modifications are formed by the filtering mechanism and terrestrial feeding mechanisms, such as grazing or pecking. Following hatching, the tongue of the domestic duck undergoes significant development, primarily in preparation for grazing activities. The anatomical and histological structure of the young (P2) tongue exhibited similarities to that of the adult female domestic duck while also displaying certain variations that could potentially be attributed to the bird's habitat and mode of feeding. RESEARCH HIGHLIGHTS: The results of this study concluded that the domestic duck exhibit a complex tongue structure characterized by the arrangement and morphology of its mechanical papillae, the presence of the lingual prominence with distinctive shape and the lingual comb. These features are believed to be adaptations that enable the duck to actively and efficiently filter food particles from water, serving as its primary feeding mechanism. Additionally, the tongue of domestic ducks is specifically adapted to facilitate various terrestrial activities, such as grazing and pecking. This adaptation is achieved through the presence of conical papillae and a lingual nail. These investigations facilitate our comprehension of both the anatomical and histological characteristics of the domestic duck tongue, as well as enhance our understanding of bird adaptations to various feeding mechanisms.

Interactions between avian viruses and skin in farm birds

This article reviews the avian viruses that infect the skin of domestic farm birds of primary economic importance: chicken, duck, turkey, and goose. Many avian viruses (e.g., poxviruses, herpesviruses, Influenza viruses, retroviruses) leading to pathologies infect the skin and the appendages of these birds. Some of these viruses (e.g., Marek's disease virus, avian influenza viruses) have had and/or still have a devasting impact on the poultry economy. The skin tropism of these viruses is key to the pathology and virus life cycle, in particular for virus entry, shedding, and/or transmission. In addition, for some emergent arboviruses, such as flaviviruses, the skin is often the entry gate of the virus after mosquito bites, whether or not the host develops symptoms (e.g., West Nile virus). Various avian skin models, from primary cells to three-dimensional models, are currently available to better understand virus-skin interactions (such as replication, pathogenesis, cell response, and co-infection). These models may be key to finding solutions to prevent or halt viral infection in poultry.

Integrated transcriptome and microbiome analyses of residual feed intake in ducks during high production period

Residual feed intake (RFI) is a crucial parameter for assessing the feeding efficiency of poultry. Minimizing RFI can enhance feed utilization and reduce costs. In this study, 315 healthy female ducks were individually housed in cages. Growth performance was monitored during the high laying period, from 290 to 325 d of age. The cecal transcriptome and microbiome of 12 ducks with high RFI and 12 with low residual feed intake (LRFI) were analyzed. Regarding growth performance, the LRFI group exhibited significantly lower RFI, feed conversion ratio (FCR), and feed intake (Fi) compared to the HRFI group (p < 0.01). However, there were no significant differences observed in body weight (BW), body weight gain (BWG), and egg mass (EML) between the groups (p > 0.05). Microbiome analysis demonstrated that RFI impacted gut microbial abundance, particularly affecting metabolism and disease-related microorganisms such as Romboutsia, Enterococcus, and Megamonas funiformis. Transcriptome analysis revealed that varying RFI changed the expression of genes related to glucose metabolism and lipid metabolism, including APOA1, G6PC1, PCK1, and PLIN1. The integrated analysis indicated that host genes were closely linked to the microbiota and primarily function in lipid metabolism, which may enhance feeding efficiency by influencing metabolism and maintaining gut homeostasis.

Identification of candidate genes affecting the tibia quality in Nonghua duck

The skeleton is a vital organ providing structural support in poultry. Weakness in bone structure can lead to deformities, osteoporosis, cage fatigue, and fractures, resulting in economic losses. Research has substantiated that genetic factors play a significant role in influencing bone quality. The discovery of genetic markers associated with bone quality holds paramount importance for enhancing genetic traits related to the skeletal system in poultry. This study analyzed nine phenotypic indicators of tibia quality in 120-day-old ducks. The phenotypic correlation revealed a high correlation among diameter, Perimeter, and weight (0.69-0.78), and a strong correlation was observed between toughness and breaking strength (0.62). Then, we conducted a genome-wide association analysis of the phenotypic indicators to elucidate the genetic basis of tibial quality in Nonghua ducks. Among the 11 candidate genes that were annotated, TAPT1, BST1, and STIM2 were related to the diameter indicator, ZNF652, IGF2BP1, CASK, and GREB1L were associated with the weight and toughness indicators. RFX8, GLP1R, and DNAAF5 were identified for ash, calcium, and phosphorus content, respectively. Finally, KEGG and GO analysis for annotated genes were performed. STIM2 and BST1 were enriched into the Calcium signalling pathway and Niacin and nicotinamide metabolic pathway, which may be key candidate genes affecting bone quality phenotypes. Gene expression analysis of the candidate genes, such as STIM2, BST1, TAPT1, and CASK showed higher expression levels in bones compared to other tissues. The obtained results can contribute to new insights into tibial quality and provide new genetic biomarkers that can be employed in duck breeding.

Duck compound probiotics fermented diet alters the growth performance by shaping the gut morphology, microbiota and metabolism

Dietary absorption and digestion are influenced by the microbiota, morphology, and digestive enzymes of intestines, and fermentation is a popular and effective technique to enhance animal rearing growth performance. This study aims to explore the pivotal role of Muscovy duck probiotics fermented feedstuff (FF) in altering the growth performance by reshaping gut morphology, microorganisms and metabolism. The findings showed that FF considerably raised the levels of fatty acids (FA) and small peptides (7-19AA) in the diet. Further feeding trial data reveals that FF greatly increased the Muscovy duck average daily gain (ADG) but had no effect on their daily feed intake (DFI), and the FCR significantly dropped (P < 0.05). Additionally, it was evident that FF improved the integrity of the intestinal mucosa in Muscovy duck by increasing villus height, villus height-to-crypt depth ratio, and lowering crypt depth. Then, in comparison to the control group (NC), there was a significant increase in the gene expression of the mucosal tight junction proteins Occludin, Claudin-1, and Zo-1 in the intestine of Muscovy duck. Additionally, there was higher expression of the mucosal transport channels SGLT-1, PepT1, AQP2, AQP3, and AQP10 in the similarly colon site, jejunum, and duodenum. Furthermore, in AB-PAS/PAS-stained duodenum, jejunum, ileum, and similarly colon site, FF markedly increased relative mucus output and goblet cells while decreasing epithelial cell apoptosis. Following 16S sequencing data indicated that the intestinal microbiota was altered and the diversity and richness of gut microbes was greatly enhanced by FF. Particularly, the boost of core probiotics, such as Rothia of duodenum, Limosilactobacillus and Lentilactobacillus of jejunum, Lactococcus and Rothia of ileum, Ligilactobacillus and Entocuccus of similarly colon site, Gallibacterium of caecum. And reduced potentially pathogenic bacteria (Campylobacter, Prevotellaceae, Clostridia-vadinBB60, and Oscillospira). Nontargeted metabolomics assay for intestinal content confirmed an increased organic acids (oxidanesulfonic acid, cholic acid, gallic acid, coumaric acid, pipecollc acid, 13s-hydroxyoctadecadienoic acid) and glycosides metabolites (5-hydroxydantrolene, 3-hydroxyguanfacine glucuronide, acetylleucine, astragalin, xanthosine, taxiphylin, sinapine, denudatine, penylalanyl-tyrosine and phenylalanyl-valine). These findings demonstrated that FF, a viable option to improve Muscovy duck growth performance through reconstructed intestinal morphology, microorganisms, and metabolism, subsequently promoted the gut health and increased diet digestion and absorption. The study that is being presented offers scientific proof that FF might be a useful strategy for improving Muscovy duck growth performance.

In-house ammonia induced lung impairment and oxidative stress of ducks

Ammonia (NH3) is a toxic gas that in intensive poultry houses, damages the poultry health and induces various diseases. This study investigated the effects of NH3 exposure (0, 15, 30, and 45 ppm) on growth performance, serum biochemical indexes, antioxidative indicators, tracheal and lung impairments in Pekin ducks. A total of 288 one-day-old Pekin male ducks were randomly allocated to 4 groups with 6 replicates and slaughtered after the 21-d test period. Our results showed that 45 ppm NH3 significantly reduced the average daily feed intake (ADFI) of Pekin ducks. Ammonia exposure significantly reduced liver, lung, kidney, and heart indexes, and lowered the relative weight of the ileum. With the increasing of in-house NH3, serum NH3 and uric acid (UA) concentrations of ducks were significantly increased, as well as liver malondialdehyde (MDA), superoxide dismutase (SOD), and glutathione peroxidase (GPX-Px) contents. High NH3 also induced trachea and lung injury, thereby increasing levels of tumor necrosis factor-α (TNF-α) and interleukin-4 (IL-4) in the lung, and decreasing the mRNA expressions of zonula occludens 1 (ZO-1) and claudin 3 (CLDN3) in the lung. In conclusion, in-house NH3 decrease the growth performance in ducks, induce trachea and lung injuries and meanwhile increase the compensatory antioxidant activity for host protection.

A novel bivalent inactivated vaccine for ducks against Riemerella anatipestifer based on serotype distribution in southern China

Riemerella anatipestifer (RA) causes epizootic infectious polyserositis in ducks with high mortality and leads to huge economic losses worldwide. Bacterial resistance poses a challenge for the control of the disease, vaccines failed to provide ideal cross-protection. Thus, the preparation of vaccines based on popular serotypes is important. In this study, we collected 700 brain and liver tissues of dead ducks from 8 provinces in southern China from 2016 to 2022 and obtained 195 RA isolates with serotypes 1, 2, 7, and 10. Serotypes 1 and 2 were the most prevalent (82%). A novel bivalent inactivated vaccine WZX-XT5 containing propolis adjuvant was prepared, we chose XT5 (serotype 1) and WZX (serotype 2) as vaccine strains and evaluated WZX-XT5-induced immune response and protective efficacy in ducks. Results showed that the XT5 (LD50, 3.5 × 103 CFU) exhibited high virulence and provided better protection against RA compared with ZXP, DCR and LCF1 (LD50, 108 CFU). Notably, the dose of 109 CFU provided ideal protection compared with 108 CFU, propolis and oil emulsion adjuvants induced stronger protective efficacy compared with aluminum hydroxide adjuvant. Importantly, WZX-XT5 immunization induced high levels of RA-specific IgY, IFN-γ, IL-2, and IL-4 in serum and offered over 90% protection against RA with ultra-high lethal dose in ducks. Additionally, no clinical signs of RA infection or obvious pathological damage in tissues were observed in protected ducks. Overall, this study first reports the identification, serotyping and virulence of RA in ducks of southern China and the preparation of a novel bivalent inactivated vaccine, providing useful scientific information to prevent and control RA infection.

Genome-wide association study for bone quality of ducks during the laying period

The cage-rearing model of the modern poultry industry makes the bones of birds, especially egg-laying birds, more vulnerable to fracture, which poses serious damage to the health of birds. Research confirms that genetic material plays an important role in regulating bone growth, development, and remodeling. However, the genetic architecture underlying bone traits is not well understood. The objectives of this study are to identify valuable genes and genetic markers through a genome-wide association study (GWAS) for breeding to improve the duck bone quality. First, we quantified the tibia and femur quality traits of 260 laying ducks. Based on GWAS, a total of 75 SNP loci significantly associated with bone quality traits were identified, and 67 potential candidate genes were annotated. According to gene function analysis, genes P4HA2, WNT3A, and BST1 et al may influence bone quality by regulating bone cell activity, calcium and phosphate metabolism, or bone collagen maturation and cross-linking. Meanwhile, combined with the transcriptome results, we found that HOXB cluster genes are also important in bone growth and development. Therefore, our findings were helpful in further understanding the genetic architecture of the duck bone quality and provided a worthy theoretical basis and technological support to improve duck bone quality by breeding.

Genome-wide characterization and comparison of endogenous retroviruses among 3 duck reference genomes

Endogenous retroviruses (ERV) are viral genomes integrated into the host genome and can be stably inherited. Although ERV sequences have been reported in some avian species' genome, the duck endogenous retroviruses (DERV) genome has yet to be quantified. This study aimed to identify ERV sequences and characterize genes near ERVs in the duck genome by utilizing LTRhavest and LTRdigest tools to forecast the duck genome and analyze the distribution of ERV copies. The results revealed 1,607, 2,031, and 1,908 full-length ERV copies in the Pekin duck (ZJU1.0), Mallard (CAU_wild_1.0), and Shaoxing duck (CAU_laying_1.0) genomes, respectively, with average lengths of 7,046, 7,027, and 6,945 bp. ERVs are mainly distributed on the 1, 2, and sex chromosomes. Phylogenetic analysis demonstrated the presence of Betaretrovirus in 3 duck genomes, whereas Alpharetrovirus was exclusively identified in the Shaoxing duck genome. Through screening, 596, 315, and 343 genes adjacent to ERV were identified in 3 duck genomes, respectively, and their functions of ERV neighboring genes were predicted. Functional enrichment analysis of ERV-adjacent genes revealed enrichment for Focal adhesion, Calcium signaling pathway, and Adherens junction in 3 duck genomes. The overlapped genes were highly expressed in 8 tissues (brain, fat, heart, kidney, liver, lung, skin, and spleen) of 8-wk-old Mallard, revealing their important expression in different tissues. Our study provides a new perspective for understanding the quantity and function of DERVs, and may also provide important clues for regulating nearby genes and affecting the traits of organisms.

Transcriptome-based comparison reveals key genes regulating allometry growth of forelimb and hindlimb bone in duck embryos

Allometric growth of the forelimb and hindlimb is a widespread phenomenon observed in vertebrates. As a typical precocial bird, ducks exhibit more advanced development of their hindlimbs compared to their forelimbs, enabling them to walk shortly after hatching. This phenomenon is closely associated with the development of long bones in the embryonic stage. However, the molecular mechanism governing the allometric growth of duck forelimb and hindlimb bones is remains elusive. In this study, we employed phenotypic, histological, and gene expression analyses to investigate developmental differences between the humerus (forelimb bone) and tibia/femur (hindlimb bones) in duck embryos. Our results revealed a gradual increase in weight and length disparity between the tibia and humerus from E12 to E28 (embryo age). At E12, endochondral ossification was observed solely in the tibia but not in the humerus. The number of differentially expressed genes (DEGs) gradually increased at H12 vs. T12, H20 vs. T20, and H28 vs. T28 stages consistent with phenotypic variations. A total of 38 DEGs were found across all 3 stages. Protein-protein interaction network analysis demonstrated strong interactions among members of HOXD gene family (HOXD3/8/9/10/11/12), HOXB gene family (HOXB8/9), TBX gene family (TBX4/5/20), HOXA11, SHOX2, and MEIS2. Gene expression profiling indicated higher expression levels for all HOXD genes in the humerus compared to tibia while opposite trends were observed for HOXA/HOXB genes with low or no expression detected in the humerus. These findings suggest distinct roles played by different clusters within HOX gene family during skeletal development regulation of duck embryo's forelimbs versus hind limbs. Notably, TBX4 exhibited high expression levels specifically in tibia whereas TBX5 showed similar patterns exclusively within humerus as seen previously across other species' studies. In summary, this study identified key regulatory genes involved in allometric growth of duck forelimb and hindlimb bones during embryonic development. Skeletal development is a complex physiological process, and further research is needed to elucidate the regulatory role of candidate genes in endochondral ossification.

Study on changing disciplinarian of beak colors in ducks and the regulation network based on transcriptome sequencing

Beak color in ducks is a primary characteristic of local breeds and genetic resources. Among them, black beaks, a rare packaging trait of high-quality duck products, have attracted much attention. In this study, Runzhou White Created ducks (black beak) and white-feathered Putian black ducks (yellow beak) were used to construct the F2 generation resource population to study the changing discipline of beak color combined with the beak color statistics of gray-beaked ducklings of Runzhou White Created ducks. Subsequently, transcriptome sequencing was performed to identify genetic markers related to beak color. To explore the rules of beak color change and its regulatory network, trends, and trend analysis and weighted gene co-expression network analysis（WGCNA）were performed. The screening results were verified by real-time quantitative polymerase chain reaction. A large difference was observed between the beak colors of birds from the F1 generation at 0 and 42 d of age. The F2 generation results show that nearly half of the black-beaked ducklings become green-beaked; the proportion of black spots for gray- and patterned-beaked ducklings increases with age, with most becoming green-beaked. Moreover, the beak color darkened from the first day, and the gray color value decreased significantly from the second day. Transcriptome sequencing indicated that TYR was differentially expressed between black and yellow beaks at 4 to 6 wk of age, and trend and WGCNA analyses showed that EDNRB signaling pathway genes and MITF were highly expressed in the first week, and TYR, TYRP1, and DCT were highly expressed at 4 to 6 wk of age. Therefore, there is melanin synthesis and deposition after hatching for gray- and patterned-beaked ducklings, while the yellow pigment might be deposited in the epidermis of beaks for black-beaked ducklings. The EDNRB signaling pathway is probably involved in early melanosome maturation and melanin formation in duck beaks, and genes such as TYR can maintain the black-beak phenotype.

A novel qPCR-based technique for identifying avian sex: An illustration within embryonic craniofacial bone

Sex is a biological variable important to consider in all biomedical experiments. However, doing so in avian embryos can be challenging as sex can be morphologically indistinguishable. Unlike humans, female birds are the heterogametic sex with Z and W sex chromosomes. The female-specific W chromosome has previously been identified in chick using a species-specific polymerase chain reaction (PCR) technique. We developed a novel reverse transcription quantitative PCR (RT-qPCR) technique that amplifies the W chromosome gene histidine triad nucleotide-binding protein W (HINTW) in chick, quail, and duck. Accuracy of the HINTW RT-qPCR primer set was confirmed in all three species using species-specific PCR, including a novel quail-specific HINTW PCR primer set. Bone development-related gene expression was then analyzed by sex in embryonic lower jaws of duck and quail, as adult duck beak size is known to be sexually dimorphic while quail beak size is not. Trends toward sex differences were found in duck gene expression but not in quail, as expected. With these novel RT-qPCR and PCR embryo sexing methods, sex of chick, quail, and duck embryos can now be assessed by either/both RNA and DNA, which facilitates analysis of sex as a biological variable in studies using these model organisms.

Analysis of Transcriptomic Differences in the Ovaries of High- and Low-Laying Ducks

The egg-laying performance of Shan Ma ducks (Anas Platyrhynchos) is a crucial economic trait. Nevertheless, limited research has been conducted on the egg-laying performance of this species. We examined routine blood indicators and observed higher levels of metabolic and immune-related factors in the high-egg-production group compared with the low-egg-production group. Furthermore, we explored the ovarian transcriptome of both high- and low-egg-production groups of Shan Ma ducks using Illumina NovaSeq 6000 sequencing. A total of 1357 differentially expressed genes (DEGs) were identified, with 686 down-regulated and 671 up-regulated in the high-egg-production (HEP) ducks and low-egg-production (LEP) ducks. Several genes involved in the regulation of ovarian development, including neuropeptide Y (NPY), cell cycle protein-dependent kinase 1 (CDK1), and transcription factor 1 (E2F1), exhibited significant differential expressions at varying stages of egg production. Pathway functional analysis revealed that the DEGs were primarily associated with the steroid biosynthesis pathway, and the neuroactive ligand-receptor interaction pathway exhibited higher activity in the HEP group compared to the LEP group. This study offers valuable information about and novel insights into high egg production.

Assessment of fungal contamination and biosecurity risk factors in duck-breeding farms in South Korea

Fungi are pathogens that infect all types of poultry and farmers, leading to economic losses in poultry production. Fungi can be isolated from environmental samples and are ubiquitous in the air. This study aimed to evaluate fungal contamination in domestic duck farm environments and analyze biosecurity risk factors associated with fungal infection incidence to assess the vulnerability of the farms to fungal infection. The average fungal concentration was 203 colony-forming units (CFU)/m3 in the air and 365 × 103 CFU/m2 in the wall surface samples. Sixteen fungal genera were recovered from air and wall surface samples from 19 duck-breeding farms, Aspergillus being the most frequently isolated (air: 43.2%; wall surface: 40%). Eleven additional fungal genera (Acrophialophora, Byssochlamys, Fusarium, Lichtheimia, Paecilomyces, Penicillium, Polycephalomyces, Rhizomucor, Scopulariopsis, Talaromyces, and Thermoascus) were isolated from air samples. Also, 8 additional fungal genera (Chaetomium, Lichtheimia, Penicillium, Petriella, Rhizomucor, Rhizopus, Talaromyces, and Trichosporon) were isolated from wall surface samples. The characteristics of the poultry farms (geographic region, stocking density, breeding house type, affiliate, duck age, and season) and fungal concentrations in the air and wall surface samples were analyzed to evaluate the biosecurity risk of the farms. Fungal infections were significantly affected by high stocking density (>2 ducks/m2), duck age (18-25 wk and >60 wk), and high fungal concentration in the wall surface samples (>300 × 103 CFU/m2).

West Nile Virus Infection in a Pekin Duck ( Anas platyrhynchos domesticus ) Developer Flock

Developer ducks are ducks being reared for breeding. Like breeder candidate chickens, they are raised with appropriate light and feed programs. A commercial Pekin duck (Anas platyrhynchos domesticus) developer flock experienced an extraordinary, elevated mortality event at 6 wk of age. Weekly mortality rate that week was 162 ducklings out of a flock of 6420 (2.5%). Mortality jumped to 988 (15.4%) ducklings the next week. On first elevated mortality, six dead ducks from that flock were submitted for diagnostic investigation at Michigan State University Veterinary Diagnostic Laboratory. Myocarditis, pale striping or diffuse pallor of the epicardium, was grossly evident in five of the six submitted ducklings. All of the ducklings had hydropericardium, three had ascites, and three had congested meninges. Histology confirmed myocarditis with myocardial necrosis. Cerebrum and brainstem had lymphocytic vasculitis with rare neuronal necrosis in affected areas, as well as Purkinje cells in the cerebellum. West Nile virus was confirmed by PCR the day after submittal and by immunohistochemistry soon thereafter.

Genetic mapping identifies SNP mutations in MITF-M promoter associated with melanin formation in Putian black duck

The coloration of plumage in poultry species has substantial economic significance. Putian black ducks encompass 2 distinct strains characterized by black and white plumage variations resulting from selective breeding. This study aimed to identify the molecular mechanisms responsible for plumage coloration in these 2 distinct strains. A comprehensive genome-wide association study was conducted using DNA data sourced from a F2 segregating population, consisting of 71 individuals with black plumage and 39 individuals with white plumage, derived from these distinct 2 strains. This analysis revealed that 894 nucleotide polymorphisms and identified 58 candidate genes. Subsequent Gene Ontology and Kyoto Encyclopedia of Genes and Genomes coenrichment analyses identified MITF as a key candidate gene implicated in melanin biosynthesis. Furthermore, extensive screening of significant polymorphic loci within MITF was carried out via mass spectrometry in 3 distinct populations: 100 individuals with black plumage and 100 individuals with white plumage from the F0 generation; and 50 with black plumage form the F1 generation). Eighteen candidate polymorphic loci were identified demonstrating significant associations with variations in black and white plumage. Notably, 8 of these loci were located within the 2,000 bp region upstream of MITF-M. To validate the critical regulatory role of MITF-M in black and white plumage formation, a dual-fluorescence reporter system was constructed, and dual-fluorescence activity was assessed. The results revealed that the fluorescence activity at wild-type sites (corresponding to black plumage) was significantly higher than that at the mutant-type sites (associated with white plumage) (P < 0.01). To corroborate the pivotal role of MITF-M in black and white plumage formation, qPCR was employed to evaluate the expression levels of various MITF variants in black and white feather bulbs. This analysis demonstrated that only MITF-M exhibited specific expression in black feather bulbs. These results elucidate the central role of polymorphic mutations within the MITF promoter region in the regulation of black and white plumage coloration in Putian black ducks. This study extends our understanding of mechanisms governing duck plumage coloration and provides valuable molecular markers for future research in duck production and breeding based on plumage coloration.

Enzyme characterization of lactic acid bacteria isolated from duck excreta

Background and Aim

The production of lignocellulosic biomass waste in the agricultural sector of Indonesia is quite high annually. Utilization of lignocellulosic biomass waste through fermentation technology can be used as feed and biofuel. Fermentation technology requires the involvement of micro-organisms such as bacteria (lactic acid bacteria or LAB). LABs can be isolated from various sources, such as duck excreta. However, there have not been many reports of LAB from duck excreta. The present study aimed to characterize LAB enzymes isolated from duck excreta and obtain LAB enzymes with superior fermentation properties.

Materials and Methods

A total of 11 LAB cultures obtained from duck excreta in Yogyakarta, Indonesia, were tested. Enzyme characterization of each LAB was performed using the API ZYM kit (BioMérieux, Marcy-I'Etoile, France). The bacterial cell suspension was dropped onto the API ZYM™ cupule using a pipette and incubated for 4 h at 37°C. After incubation, ZYM A and ZYM B were dripped onto the API ZYM cupule, and color changes were observed for approximately 10 s under a strong light source.

Results

Esterase activity was moderate for all LABs. The activity of α-chymotrypsin, β-glucuronidase, α-fucosidase, and α-mannosidase was not observed in a total of 10 LAB. The phosphohydrolase and amino peptidase enzyme activity of seven LABs was strong. Only six LAB samples showed protease activity. The glycosyl hydrolase (GH) activity was observed in a total of 8 LAB, while the activity of 2 LAB was strong (Lactococcus lactis subsp. lactis K5 and Lactobacillus brevis M4A).

Conclusion

A total of 2 LABs have superior properties. L. lactis subsp. lactis K5 and L. brevis M4A have a high potential to be used in fermentation. They have the potential for further research, such as their effectiveness in fermentation, lignocellulose hydrolysis, feed additives, molecular characterization to detect specific enzymes, and their specific activities.

Genome-Wide Association Studies Reveal Candidate Genes Associated with Pigmentation Patterns of Single Feathers of Tianfu Nonghua Ducks

In modern advanced genetics and breeding programs, the study of genes related to pigmentation in ducks is gaining much attention and popularity. Genes and DNA mutation cause variations in the plumage color traits of ducks. Therefore, discovering related genes responsible for different color traits and pigment patterns on each side of the single feathers in Chinese ducks is important for genetic studies. In this study, we collected feather images from 340 ducks and transported them into Image Pro Plus (IPP) 6.0 software to quantify the melanin content in the feathers. Thereafter, a genome-wide association study was conducted to reveal the genes responsible for variations in the feather color trait. The results from this study revealed that the pigmented region was larger in the male ducks as compared to the female ducks. In addition, the pigmented region was larger on the right side of the feather vane than on the left side in both dorsal and ventral feathers, and a positive correlation was observed among the feather color traits. Further, among the annotated genes, WNT3A, DOCK1, RAB1A, and ALDH1A3 were identified to play important roles in the variation in pigmented regions of the various feathers. This study also revealed that five candidate genes, including DPP8, HACD3, INTS14, SLC24A1, and DENND4A, were associated with the color pigment on the dorsal feathers of the ducks. Genes such as PRKG1, SETD6, RALYL, and ZNF704 reportedly play important roles in ventral feather color traits. This study revealed that genes such as WNT3A, DOCK1, RAB1A, and ALDH1A3 were associated with different pigmentation patterns, thereby providing new insights into the genetic mechanisms of single-feather pigmentation patterns in ducks.

Draft genome sequence of multidrug-resistant Citrobacter portucalensis BAU_133-2 strain isolated from a domestic duck (Anas platyrhynchos domesticus) in Bangladesh

We announce the genome sequence of the Citrobacter portucalensis BAU_133-2 strain isolated from a domestic duck. Our assembled genome contained a length of 4.8 Mb, 110.0× genome coverage, 51.91% of an average GC content, 1 plasmid, 1 CRISPR array, 8 prophages, 27 antibiotic resistance genes, and 75 virulence factor genes.

Characterization and comparative transcriptomic analysis of skeletal muscle in female Pekin duck and Hanzhong Ma duck during different growth stages using RNA-seq

Duck is an economically important poultry, and there is currently a major focus on improving its meat quality through breeding. There are wide variations in the growth regulation mechanisms of different duck breeds, that fundamental research on skeletal muscle growth is essential for understanding the regulation of unknown genes. The study aimed to broaden the understanding the duck skeletal muscle development and thereby to improve the performance of domestic ducks. In this study, RNA-seq data from skeletal muscles (breast muscle and leg muscle) of Pekin duck and Hanzhong Ma duck sampled at d 17, 21, and 27 of embryo (E17d, E21d, and E27d), as well as at 6-mo-old following birth (M6), to investigate and compare the mRNA temporal expression profiles and associated pathways that regulate skeletal myogenesis of different duck breeds. There were 331 to 1,440 annotated differentially expressed genes (DEGs) in breast muscle and 380 to 1,790 annotated DEGs in leg muscle from different databases between 2 duck breeds. Gene ontology (GO) enrichment in skeletal muscles indicated that these DEGs were mainly involved in biosynthetic process, developmental process, regulation of protein metabolic process and regulation of gene expression. KEGG analysis in skeletal muscles showed that a total of 41 DEGs were mapped to 7 KEGG pathways, including ECM-receptor interaction, focal adhesion, carbon metabolism, regulation of actin cytoskeleton, calcium signaling pathway, biosynthesis of amino acids and PPAR signaling pathway. The differential expression of 8 selected DEGs was verified by qRT-PCR, and the results were consistent with RNA-seq data. The identified DEGs, such as SDC, SPP1, PAK1, MYL9, PGK1, NOS1, PHGDH, TNNT2, FN1, and AQP4, were specially highlighted, indicating their associations with muscle development in the Pekin duck and Hanzhong Ma duck. This study provides a basis for revealing the differences in skeletal muscle development between Pekin duck and Hanzhong Ma duck.

Immunopromoter improves liver apoptosis and immune response in Shaoxing ducklings

Antibiotics as feed additives, play a vital role in animal husbandry. However, overused antibiotics could cause endogenous infections in animals, and even endanger human health through the food chain. And immunopotentiators can make the low immune function improve and accelerate the induction of immune response. The aim of this study was to investigate the effects of five different immunopotentiators on the expression of liver apoptosis and immune factor related genes in Shaoxing ducklings (Anas Platyrhynchos). A total of 150 one-day-old Shaoxing ducklings were randomly divided into six groups including saline, chlorogenic acid, β-D-glucan, astragalus flavone, CpG DNA and chicken IgG, which were injected subcutaneously into the neck, respectively. At 18 days old, the liver tissues were collected to detecte the mRNA and protein expression levels of inflammatory and apoptosis-related genes. The results showed that compared with the control group, the mRNA and protein levels of liver Bcl2 with chlorogenic acid, β-D-glucan, astragalus flavone, CpG-DNA and chicken IgG were significantly decreased (p < 0.05), while the expression level of Caspase3 was up-regulated in some different degrees. In addition,The expression levels of liver iNOS and COX2 were significantly increased after the injection of five immunopotentiators (p < 0.05), and the mRNA levels of IFN-α, IFN-β, IL-1β, RIG-I, TLR3 and TLR7 genes were also significantly up-regulated compared with the control group (p < 0.05). In conclusion, chlorogenic acid, β-D-glucan, astragalus flavone, CpG-DNA and chicken IgG can be used as immunopotentiators to regulate duck innate immunity. This study provides a new way to prevent important infectious diseases of ducks, and also provides a certain reference for the application of antibiotic substitutes in animal production.

Research Note: Transcriptome analysis reveals differentially expressed genes regulated muscle development in Pekin ducks during dietary threonine deficiency

To investigate the underlying molecular mechanism of threonine (Thr) regulation on the development of breast muscle in Pekin ducks, 240 male Pekin ducks at 1 d of age were fed a Thr deficiency diet (Thr-D), Thr sufficiency diet (Thr-S), or Thr excess diet (Thr-E) for 21 d. The results showed that Thr-D reduced body weight (BW), average weight gain (ADG), and average feed intake (ADFI), and increased the feed/gain (F/G) in Pekin ducks (P < 0.05), and Thr-E did not affect BW, ADG, ADFI, or F/G (P > 0.05), compared with Thr-S. The diameter and cross-sectional area of the breast muscle fibers in the Thr-S group were larger than those in the Thr-D group (P < 0.05). RNA sequencing revealed 1,300 differential expressed genes (DEGs) between the Thr-D and Thr-S groups, of which 625 were upregulated and 675 were downregulated by Thr-D. KEGG analysis showed that the upregulated genes were enriched in mTOR, FoxO, Wnt, fat digestion and absorption, and other signaling pathways. The downregulated genes were enriched in the MAPK signaling, glycolysis/gluconeogenesis, adipocytokine signaling, and biosynthesis of unsaturated fatty acids signaling pathways. The genes of Wnt family member 3a (Wnt3a), myogenin, myozenin 2, and insulin like growth factor 2 mRNA binding protein were upregulated, and platelet derived growth factor subunit B, PDGF receptor beta and Wnt4 were downregulated by Thr deficiency, which involving in muscle development. Our findings indicated that Thr increased breast fiber size, perhaps because Thr affected the proliferation and differentiation of satellite cells in breast muscle of ducks after hatch. Our results provide novel insights into new understanding of the molecular mechanisms underlying breast muscle development in ducks subjected to dietary Thr.

Development of a reverse transcription loop-mediated isothermal amplification based clustered regularly interspaced short palindromic repeats Cas12a assay for duck Tembusu virus

Duck Tembusu virus (DTMUV) is an emerging pathogen that poses a serious threat to the duck industry in China. Currently, polymerase chain reaction (PCR), quantitative PCR (qPCR) and reverse transcription loop-mediated isothermal amplification (RT-LAMP) are commonly used for DTMUV detection. However, these methods require complex steps and special equipment and easily cause false-positive results. Therefore, we urgently need to establish a simple, sensitive and specific method for the clinical field detection of DTMUV. In this study, we developed an RT-LAMP-based CRISPR-Cas12a assay targeting the C gene to detect DTMUV with a limited detection of 3 copies/μL. This assay was specific for DTMUV without cross-reaction with other common avian viruses and only required some simple pieces of equipment, such as a thermostat water bath and blue/UV light transilluminator. Furthermore, this assay showed 100% positive predictive agreement (PPA) and negative predictive agreement (NPA) relative to SYBR Green qPCR for DTMUV detection in 32 cloacal swabs and 22 tissue samples, supporting its application for clinical field detection.

Environmental Cadmium Exposure Perturbs Gut Microbial Dysbiosis in Ducks

Ore extraction, chemical production, and agricultural fertilizers may release significant amounts of heavy metals, which may eventually accumulate widely in the environment and organisms over time, causing global ecological and health problems. As a recognized environmental contaminant, cadmium has been demonstrated to cause osteoporosis and renal injury, but research regarding the effects of cadmium on gut microbiota in ducks remains scarce. Herein, we aimed to characterize the adverse effects of cadmium on gut microbiota in ducks. Results indicated that cadmium exposure dramatically decreased gut microbial alpha diversity and caused significant changes in the main component of gut microbiota. Moreover, we also observed significant changes in the gut microbial composition in ducks exposed to cadmium. A microbial taxonomic investigation showed that Firmicutes, Bacteroidota, and Proteobacteria were the most preponderant phyla in ducks regardless of treatment, but the compositions and abundances of dominant genera were different. Meanwhile, a Metastats analysis indicated that cadmium exposure also caused a distinct increase in the levels of 1 phylum and 22 genera, as well as a significant reduction in the levels of 1 phylum and 36 genera. In summary, this investigation demonstrated that cadmium exposure could disturb gut microbial homeostasis by decreasing microbial diversity and altering microbial composition. Additionally, under the background of the rising environmental pollution caused by heavy metals, this investigation provides a crucial message for the assessment of environmental risks associated with cadmium exposure.

The first report of polymorphisms of the prion protein gene (PRNP) in Pekin ducks (Anas platyrhynchos domestica)

Background

Prion diseases have been extensively reported in various mammalian species and are caused by a pathogenic prion protein (PrPSc), which is a misfolded version of cellular prion protein (PrPC). Notably, no cases of prion disease have been reported in birds. Single nucleotide polymorphisms (SNPs) of the prion protein gene (PRNP) that encodes PrP have been associated with susceptibility to prion diseases in several species. However, no studies on PRNP polymorphisms in domestic ducks have been reported thus far.

Method

To investigate PRNP polymorphisms in domestic ducks, we isolated genomic DNA from 214 Pekin duck samples and sequenced the coding region of the Pekin duck PRNP gene. We analyzed genotype, allele, and haplotype distributions and linkage disequilibrium (LD) among the SNPs of the Pekin duck PRNP gene. In addition, we evaluated the effects of the one non-synonymous SNP on the function and structure of PrP using the PROVEAN, PANTHER, SNPs & GO, SODA, and AMYCO in silico prediction programs.

Results

We found five novel SNPs, c.441 T > C, c.495 T > C, c.582A > G, c.710C > T(P237L), and c.729C > T, in the ORF region of the PRNP gene in 214 Pekin duck samples. We observed strong LD between c.441 T > C and c.582A > G (0.479), and interestingly, the link between c.495 T > C and c.729C > T was in perfect LD, with an r2 value of 1.0. In addition, we identified the five major haplotype frequencies: TTACC, CTGCC, CTACC, CCGCT, and CTATC. Furthermore, we found that the non-synonymous SNP, c.710C > T (P237L), had no detrimental effects on the function or structure of Pekin duck PrP. However, the non-synonymous SNP had deleterious effects on the aggregation propensity and solubility of Pekin duck PrP compared with wildtype Pekin duck PrP.

Conclusion

To the best of our knowledge, this study is the first report on the genetic characteristics of PRNP SNPs in Pekin ducks.

Metabolomic characterization of Liancheng white and Cherry Valley duck breast meat and their relation to meat quality

Liancheng white duck is a typical local duck breed in Fujian Province famous for its meat traits. To better understand how meat quality varies with breed, the chemical composition of breast meats of Liancheng white ducks (LD) and Cherry Valley ducks (CD) were examined using ultra-high-performance liquid chromatography quadrupole time-of-flight mass spectrometry (UHPLC-QTOF-MS).The correlation between meat quality and the differential metabolites was further analyzed. The results showed that the effects of breed on duck breast meat were significant for pH, color, cooking loss, and shear force. Liancheng white duck breast meat exhibited a higher shear force and pH, and lower cooking loss and lightness (L*24), redness (a*24), and yellowness (b*24) than CD. Metabolomic analysis revealed significant differences between the meat extracts from the 2 duck breeds. A total of 49 and 57 significantly different metabolites were identified in positive and negative ion modes, respectively. These differentially accumulated metabolites (DAMs) could be divided into 28 classes, of which the 4 main categories were carbohydrates, amino acids, fatty acids, and eicosanoids. Liancheng white duck might have better nutritional and medicinal value considering the higher content of (4Z,7Z,10Z,13Z,16Z,19Z)-4,7,10,13,16,19-docosahexaenoic acid (DHA), docosapentaenoic acid (DPA), eicosapentaenoic acid (EPA), and prostaglandinF3α (PGF3α), having anti-inflammatory orantioxidant effects. Carbohydrate concentration negatively correlated with pH24. The 4 metabolites positively correlated with the shear force. These results provide an overall perspective for bridging the gap between variation of duck meat quality and metabolites with respect to breed.

Pharmacokinetics and bioavailability of meloxicam in Pekin ducks following intravenous, intramuscular and oral administration

OBJECTIVE

To determine the pharmacokinetics and bioavailability of meloxicam following intravenous (IV), intramuscular (IM), and oral administrations at a dose of 1.0 mg kg-1 in Pekin ducks.

STUDY DESIGN

Randomized experimental trial.

ANIMALS

A total of 18 clinically healthy male Pekin ducks.

METHODS

Pekin ducks were randomly assigned to three groups of six ducks: IV, IM and oral. Meloxicam (1.0 mg kg-1) was administered to each Pekin duck. A non-compartmental analysis was used to evaluate pharmacokinetic parameters.

RESULTS

No local or systemic adverse effects were observed in any bird. Meloxicam was detected in the plasma up to 120 hours following IV, IM or oral administration. The elimination half-life of the IV route was slightly shorter than that of the IM and oral routes (p < 0.05). Following IV administration, volume of distribution at steady state and total clearance were 133.17 mL kg-1 and 6.68 mL kg-1 hour-1, respectively. The mean absorption time was 2.29 hours for IM and 1.13 hours for oral route. There were significant differences between IM and oral administration for the peak plasma concentration (Cmax), time to reach Cmax and bioavailability (p < 0.05).

CONCLUSIONS AND CLINICAL RELEVANCE

Meloxicam showed long elimination half-life and high bioavailability following IM and oral administration. Meloxicam in Pekin ducks provided the effective therapeutic concentration indicated in other species for up to 48 hours. However, there is a need to determine the clinical efficacy of meloxicam in Pekin ducks.

Argas persicus and Carios vespertilionis Ticks Infesting Ducks, Domestic Fowls and Bats in Pakistan: First Report on Molecular Survey and Phylogenetic Position of Borrelia anserina

Argasid ticks have the vectorial potential for transmitting disease-causing pathogens to avian hosts, resulting in economic losses that may not be fully estimated. Borrelia species are the responsible agents of borreliosis in poultry, animals and humans. Our previous studies have reported a high prevalence of Argas persicus infesting domestic fowls in Khyber Pakhtunkhwa (KP), Pakistan. However, molecular screening and genetic characterization of Borrelia spp. in A. persicus have been neglected in Pakistan. In this study, we focused on the molecular epidemiology and genetic characterization of Borrelia spp. associated with A. persicus ticks infesting domestic fowls and ducks, and Carios vespertilionis infesting bats in selected districts of KP. Overall, 1818 ticks, including females (415; 23%), males (345; 19%), nymphs (475; 26%) and larvae (583; 32%), were collected from 27 locations in nine districts (Peshawar, Mardan, Swabi, Charsadda, Chitral, Lakki Marwat, Bannu, Bajaur and Hangu) from domestic fowls, ducks and their shelters, and bats. A subset of 197 ticks was selected for DNA extraction and PCR to amplify fragments of the cytochrome c oxidase (cox) gene for ticks and flagellin B (flaB) for the detection and genetic characterization of associated Borrelia spp. Among these, only Borrelia anserina DNA was detected in 40 ticks (27.2%) of different life stages, where highest prevalence was found in female ticks (18; 45%), followed by nymphs (12; 30%), larvae (7; 17.5%) and males (3; 7.5%). Tick infestation in shelters (1081; 77%) was higher than on hosts (323; 23%). The resultant cox amplicons of A. persicus showed 100% identity with the same species reported from Pakistan, China, Iran, Kenya, Kazakhstan, Algeria and Egypt and C. vespertilionis show 100% identity with the species reported from Pakistan, China, Japan, Kenya, Vietnam, Spain, Netherlands, the United Kingdom and Hungry, and clustered with the aforementioned species in the phylogenetic tree. The obtained Borrelia sequences showed 100% identity with B. anserina and revealed a close resemblance to the relapsing fever group and clustered in a monophyletic clade with B. anserina from India, Iran and Brazil in a phylogenetic tree. These results establish the first molecular characterization of B. anserina in A. persicus infesting domestic fowls and ducks in the region, as well as their shelters. To effectively control zoonotic consequences, country-wide surveillance research should be encouraged to screen soft ticks infesting various birds for associated pathogens.

Research Note: Evaluation of standardized ileal amino acid digestibility in feed ingredients for Pekin ducks

The digestibility of crude protein (CP) and amino acids (AA) in feedstuffs including corn, soybean meal (SBM), and corn distillers dried grains with solubles (DDGS) was investigated in White Pekin ducks. The test ingredients were the sole source of AA and CP. A nitrogen-free diet was also formulated for determining endogenous losses of AA and nitrogen. Birds were fed a standard starter diet for the first 15 d posthatch. On d 16, 96 ducklings (860 ± 50 g BW) were selected and allocated into 1 of 4 dietary treatments containing the test ingredients with 6 replicates per treatment in a randomized complete block design. All the crumbled assay diets were offered ad-libitum for 5 d and contained chromic oxide as an indigestible marker at 0.05%. On d 21, ducks were euthanized to collect the ileal digesta for digestibility analysis. Basal endogenous losses were abundant in glutamine, aspartic acid, leucine, proline, and serine, consecutively. For apparent ileal digestibility (AID), lysine and methionine were the highest (P < 0.05) in SBM, followed by corn and DDGS. For threonine, the highest values (P < 0.05) were similarly noted for SBM, followed by DDGS and corn; the values were 80.44, 69.88, and 64.89%, consecutively. Considering standardized ileal digestibility (SID), higher values (P < 0.05) for SBM were similarly noted for all the amino acids including lysine, methionine, and threonine; the values were 89.40, 93.58, and 86.50%, respectively. Conclusively, improved AA and CP digestibility was noted with SBM. Dietary protein source affected the extent of digestibility at the distal ileum; and the utilization of digestible amino acid coefficients during ducks' feed formulation is emphasized.

Comparative transcriptome analysis reveals mechanisms of restriction feeding on lipid metabolism in ducks

Presently, excessive fat deposition is the main reason to limit the development of duck industry. In the production, the methods of restricted feeding (RF) were widely used to reduce the lipid deposition of ducks. The liver (L), abdominal adipose (AA), and subcutaneous adipose (SA) were the main tissues of lipid metabolism and deposition of ducks. However, the mechanisms of lipid metabolism and deposition of ducks under RF have not been fully clarified. In this study, in order to better understand the mechanisms of lipid metabolism and deposition in ducks under RF, a total of 120 male Nonghua ducks were randomly divided into a free feeding group (FF, n = 60) and RF group (RF, n = 60), then comparative transcriptomic analysis of L, AA, and SA between FF (n = 3) and RF (n = 3) ducks was performed at 56 d of age. Phenotypically, L, AA, and SA index of FF group was higher than that in RF group. There were 279, 390, and 557 differentially expressed genes (DEGs) in L, AA, and SA. Functional enrichment analysis revealed that ECM-receptor interaction and metabolic pathways were significantly enriched in L, AA, and SA. Lipid metabolism-related pathways including fatty acid metabolism, unsaturated fatty acid synthesis, and steroidogenesis were significantly enriched in AA and SA. Moreover, through integrated analysis weighted gene coexpression network (WGCNA) and protein-protein interaction network, 10 potential candidate genes involved in the ECM-receptor interaction and lipid metabolism pathways were identified, including 3-hydroxy-3-methylglutaryl-CoA synthase 2 (HMGCS2), aldolase B (ALDOB), formimidoyltransferase cyclodeaminase(FTCD), phosphoenolpyruvate carboxykinase 1 (PCK1), tyrosine aminotransferase (TAT), stearoyl-CoA desaturase (SCD), squalene epoxidase (SQLE), phosphodiesterase 4B (PDE4B), choline kinase A (CHKA), and elongation of very-long-chain fatty acids-like 2 (ELOVL2), which could play a key role in lipid metabolism and deposition of ducks under RF. Our study reveals that the liver might regulate the lipid metabolism of abdominal adipose and subcutaneous adipose through ECM-receptor interaction and metabolic pathways (fatty acid metabolism, unsaturated fatty acid synthesis, and steroid synthesis), thus to reduce the lipid deposition of ducks under RF. These results provide novel insights into the avian lipid metabolism and will help better understand the underlying molecular mechanisms.

Effects of linseed oil supplementation duration on fatty acid profile and fatty acid metabolism-related genes in the muscles of Chinese crested white ducks

Meat rich in polyunsaturated fatty acids is considered beneficial to health. Supplementing the diet with linseed oil promotes the deposition of polyunsaturated fatty acids (PUFAs) in poultry, a conclusion that has been confirmed multiple times in chicken meat. However, fewer studies have focused on the effects of dietary fatty acids on duck meat. Therefore, this study aims to evaluate the effects of the feeding time of a linseed oil diet on duck meat performance and gene expression, including meat quality performance, plasma biochemical indicators, fatty acid profile, and gene expression. For this study, we selected 168 Chinese crested ducks at 28 days old and divided them into three groups, with 56 birds in each group. The linseed oil content in the different treatment groups was as follows: the control group (0% flaxseed oil), the 14d group (2% linseed oil), and the 28d group (2% linseed oil). Ducks in the two experimental groups were fed a linseed oil diet for 28 and 14 days at 28 and 42 days of age, respectively. The results showed that linseed oil had no negative effect on duck performance (slaughter rate, breast muscle weight, and leg muscle weight) or meat quality performance (pH, meat color, drip loss, and shear force) (P > 0.05). The addition of linseed oil in the diet increased plasma total cholesterol and high-density lipoprotein cholesterol levels (P < 0.05), while decreasing triglyceride content (P < 0.05). Furthermore, the supplementation of linseed oil for four weeks affected the composition of muscle fatty acids. Specifically, levels of α-linolenic acid, eicosapentaenoic acid, and docosahexaenoic acid were increased (P < 0.05), while eicosatetraenoic acid content was negatively correlated with flaxseed oil intake (P < 0.05). qRT-PCR analysis further revealed that the expression of FATP1, FABP5, and ELOVL5 genes in the breast muscle, as well as FABP3 and FADS2 genes in the thigh muscle, increased after four weeks of linseed oil supplementation (P < 0.05). However, after two weeks of feeding, CPT1A gene expression inhibited fatty acid deposition, suggesting an increase in fatty acid oxidation (P < 0.05). Overall, the four-week feeding time may be a key factor in promoting the deposition of n-3 PUFAs in duck meat. However, the limitation of this study is that it remains unknown whether longer supplementation time will continue to affect the deposition of n-3 PUFAs. Further experiments are needed to explain how prolonged feeding of linseed oil will affect the meat quality traits and fatty acid profile of duck meat.

Comprehensive transcriptomic and metabolomic analysis of the effect of feed restriction on duck sternal development

Skeletal characteristics are important to the growth and development of poultry. In feeding management, constant free feeding (FF) of poultry may lead to imbalance between bone development and weight gain. Feed restriction (FR), to a certain extent, is one way to solve this problem. However, the effect of feed restriction on poultry bone development needs further elucidation at the molecular level. Therefore, in the present study, we investigated the effects of different levels of feed restriction (60% FR, 70% FR, 80% FR, and FF) on the sternum development of ducks at 7 and 8 wk old. In the seventh wk, with increasing feed restriction, the values of traits including body weight, breast muscle weight, sternal weight, keel length, and calcified keel length decreased. However, in the eighth wk, the sternum weight and keel length of ducks treated with 60% FR were unexpectedly higher than those of FF individuals, indicative of catch-up growth. Then, we conducted RNA-seq and metabolomic analysis on sterna from 7- and 8-wk-old FF and 60% FR ducks. The results identified multiple differentially expressed genes (DEGs) associated with sternum development that were influenced by feed restriction. Among them, we found that the mRNA expression levels of the chondroitin sulfate synthase 3 (CHSY3) and annexin A2 (ANXA2) which are involved in glycosaminoglycan biosynthesis and bone mineralization, had smaller changes over time under FR treatment than under FF treatment, implying that the FR treatment to a certain extent prevented the premature calcification and prolonged the development time of duck sternum. In addition, the metabolomic and integrative analyses revealed that several antiaging-related metabolites and genes were associated with sternal catch-up growth. Pyrimidine metabolism was identified as the most significant pathway in which most differential metabolites (DMs) between FF and 60% FR were enriched. The results from integrative analysis revealed that the content and expression of 4-aminobutyric acid (GABA) and its related genes showed relatively higher activity in the 60% FR group than in the FF group. The present study identifies multiple biomarkers associated with duck sternum development that are influenced by feed restriction and suggests the potential mechanism of feed restriction-associated duck sternal catch-up growth.

Isolation and characterization of a novel goose ovaritis-associated cluster 3 Tembusu virus

Tembusu virus (TMUV) is a member of the genus Flavivirus in the family Flaviviridae. Currently, TMUV was classified into 4 distinct clusters, with cluster 2 strains widely distributed in duck and goose populations in Asia, causing significant economic losses to the producing industries. In this study, a novel TMUV strain TMUV/goose/CHN/2019/HNU-NX2 (HNU-NX2-2019) was isolated and characterized from geese with ovaritis from Hunan province, China. Phylogenetic analyses of genome and the E gene indicated the present TMUV could be grouped into the newly defined TMUV cluster 3. The genome of HNU-NX2-2019 showed the highest identities of 98.1% to 98.2% to the cluster 3 TMUVs newly identified in 2020 and 2021 from chickens with a severe egg-drop syndrome from Guangdong, Guangxi and Shandong provinces of China, which were all showing a close relation to a mosquito-origin TMUV (KT607936) identified in 2012. Further experiments confirmed HNU-NX2-2019 could grow well in chicken fibroblast cell line DF-1 and in SPF chicken embryos, with titers varied from 107.3 to 108.8 viral genomic copies per mL in the culture solutions. A pilot virus challenge study in 3-day-old chicks demonstrated that this virus could efficiently infect chicks with virus distributed in the brains, small intestines and other visceral organs, with titers varied from 105.4 to 106.7viral genomic copies per gram of the tissues. Furthermore, HNU-NX2-2019 can induce specific antibody in ducklings but with no obvious disease and virus shedding, and on necropsy no TMUV was detected in the tissues in the present study. This is the first report to identify a novel cluster 3 TUMV from goose, and further demonstrated this goose TMUV strain could infect chicken efficiently but not in ducklings under the present experimental conditions, which highlighted intensive attentions may be paid to this novel mosquito-origin cluster 3 TMUV.

Reduced Nitric Oxide Synthase Involvement in Aigamo Duck Basilar Arterial Relaxation

The basilar arterial endothelium mediates blood vessel relaxation partly through the release of nitric oxide (NO). Apoptosis of cerebrovascular endothelial cells is linked to a high mortality rate in chickens infected with the highly pathogenic avian influenza virus, but interestingly, ducks exhibit a greater resistance to this virus. In this study, we examined the responsiveness of duck basilar arteries (BAs) to various vasoactive substances, including 5-hydroxytryptamine (5-HT), histamine (His), angiotensin (Ang) II, noradrenaline (NA), acetylcholine (ACh), and avian bradykinin ornithokinin (OK), aiming to characterize the receptor subtypes involved and the role of endothelial NO in vitro. Our findings suggest that arterial contraction is mediated with 5-HT1 and H1 receptors, while relaxation is induced with β3-adrenergic and M3 receptors. Additionally, OK elicited a biphasic response in duck BAs, and Ang II had no effect. Endothelial NO appears to be crucial in relaxation mediated with M3 and OK receptors but not β3-adrenergic receptors in the duck BA. The reduced endothelial NO involvement in the receptor-mediated relaxation response in duck BAs represents a clear difference from the corresponding response reported in chicken BAs. This physiological difference may explain the differences in lethality between ducks and chickens when vascular endothelial cells are infected with the virus.

Identification of SNPs in MITF associated with beak color of duck

Introduction: Beak color-a pigment-related trait-is an important feature of duck breeds. Recently, little research has addressed genetic mechanism of the beak colors in poultry, whereas the process and the regulation factors of melanin deposition have been well described. Methods: To investigate the genetic mechanism of beak colors, we conducted an integrated analysis of genomic selection signatures to identify a candidate site associated with beak color. For this, we used black-billed (Yiyang I meat duck synthetic line H1, H2, H3&HF) and yellow-billed ducks (Cherry Valley ducks and white feather Putian black duck). Quantitative real-time PCR and genotyping approaches were used to verify the function of the candidate site. Results: We identified 3,895 windows containing 509 genes. After GO and KEGG enrichment analysis, nine genes were selected. Ultimately, MITF was selected by comparing the genomic differentiation (FST). After loci information selection, 41 extreme significantly different loci were selected, which are all located in intron regions of MITF and are in almost complete linkage disequilibrium. Subsequently, the site ASM874695v1:10:g.17814522T > A in MITF was selected as the marker site. Furthermore, we found that MITF expression is significantly higher in black-beaked ducks than in yellow-beaked ducks of the F2 generation (p < 0.01). After genotyping, most yellow-billed individuals are found with homozygous variant; at the same time, there are no birds with homozygous variant in black-billed populations, while the birds with homozygous and heterozygous variant share the same proportion. Conclusion: MITF plays a very critical role in the melanogenesis and melanin deposition of duck beaks, which can effectively affect the beak color. The MITF site, ASM874695v1:10:g.17814522T > A could be selected as a marker site for the duck beak color phenotype.

Age is a determinant factor in the susceptibility of domestic ducks to H5 clade 2.3.2.1c and 2.3.4.4e high pathogenicity avian influenza viruses

High pathogenicity avian influenza (HPAI) is a viral disease with devastating consequences for the poultry industry worldwide. Domestic ducks are a major source of HPAI viruses in many Eurasian countries. The infectivity and pathogenicity of HPAI viruses in ducks vary depending on host and viral factors. To assess the factors influencing the infectivity and pathogenicity of HPAI viruses in ducks, we compared the pathobiology of two HPAI viruses (H5N1 clade 2.3.2.1c and H5N6 clade 2.3.4.4e) in 5- and 25-week-old ducks. Both HPAI viruses caused mortality in a dose-dependent manner (104, 106, and 108 EID50) in young ducks. By contrast, adult ducks were infected but exhibited no mortality due to either virus. Viral excretion was higher in young ducks than in adults, regardless of the HPAI strain. These findings demonstrate the age-dependent mortality of clade 2.3.2.1c and clade 2.3.4.4e H5 HPAI viruses in ducks.

Comparative Investigation of Coincident Single Nucleotide Polymorphisms Underlying Avian Influenza Viruses in Chickens and Ducks

Avian influenza is a severe viral infection that has the potential to cause human pandemics. In particular, chickens are susceptible to many highly pathogenic strains of the virus, resulting in significant losses. In contrast, ducks have been reported to exhibit rapid and effective innate immune responses to most avian influenza virus (AIV) infections. To explore the distinct genetic programs that potentially distinguish the susceptibility/resistance of both species to AIV, the investigation of coincident SNPs (coSNPs) and their differing causal effects on gene functions in both species is important to gain novel insight into the varying immune-related responses of chickens and ducks. By conducting a pairwise genome alignment between these species, we identified coSNPs and their respective effect on AIV-related differentially expressed genes (DEGs) in this study. The examination of these genes (e.g., CD74, RUBCN, and SHTN1 for chickens and ABCA3, MAP2K6, and VIPR2 for ducks) reveals their high relevance to AIV. Further analysis of these genes provides promising effector molecules (such as IκBα, STAT1/STAT3, GSK-3β, or p53) and related key signaling pathways (such as NF-κB, JAK/STAT, or Wnt) to elucidate the complex mechanisms of immune responses to AIV infections in both chickens and ducks.

Generation of a monoclonal antibody against duck circovirus capsid protein and its potential application for native viral antigen detection

Introduction

Duck circovirus (DuCV) infection is currently recognized as an important immunosuppressive disease in commercial duck flocks in China. Specific antibodies against DuCV viral proteins are required to improve diagnostic assays and understand the pathogenesis of DuCV infection.

Methods and results

To generate DuCV-specific monoclonal antibodies (mAbs), a recombinant DuCV capsid protein without the first 36 N-terminal amino acids was produced in Escherichia coli. Using the recombinant protein as an immunogen, a mAb was developed that reacted specifically with the DuCV capsid protein, expressed in E. coli and baculovirus systems. Using homology modeling and recombinant truncated capsid proteins, the antibody-binding epitope was mapped within the region of ¹⁴⁴IDKDGQIV¹⁵¹, which is exposed to solvent in the virion capsid model structure. To assess the applicability of the mAb to probe the native virus antigen, the murine macrophage cell line RAW267.4 was tested for DuCV replicative permissiveness. Immunofluorescence and Western blot analysis revealed that the mAb recognized the virus in infected cells and the viral antigen in tissue samples collected from clinically infected ducks.

Discussion

This mAb, combined with the in vitro culturing method, would have widespread applications in diagnosing and investigating DuCV pathogenesis.

Fatty Acid Profile, Health Lipid Indices, and Sensory Properties of Meat from Pekin Ducks of Different Origins

Conservation duck flocks are of significant importance to science. Over a number of years, many experiments have been carried out to gain a better understanding of individual duck populations. However, the knowledge obtained is still incomplete. The aim of the present study was to compare three duck strains maintained in Poland and included in the Genetic Resources Protection Programme in terms of the fatty acid profile, health lipid indices, and sensory traits of breast and leg meat. The experimental material consisted of 180 sexed Pekin ducks, 60 ducks each (including 30 males and 30 females) from strain P33 (Pekin of Polish origin), P8 (Pekin of Danish origin), and P9 (Pekin of French origin). During 49 days of rearing, the ducks were kept in an enclosed building with six pens on straw. The duck genotype had a significant effect on the myristic (C14:0), palmitic (C16:0), oleic (C18:1n9), linolenic (C18:2n6), arachidonic (C20:4n6), monounsaturated fatty acid (MUFA), PUFAn6 content, and Peroxidisability Index (PI) values of breast muscle. Ducks from the compared strains differed significantly in C16:0 content and the proportion of unsaturated fatty acids (UFAs), including MUFAs, Nutritive Value Index, and Health-Promoting Index in leg muscles. Ducks from the compared strains also differed significantly in the aroma and juiciness of the heat-treated breast muscles and the tenderness of the leg muscles. The sex of the birds had a significant effect on the C18:1, C22:6n3, MUFA, PUFAn6, PUFAn3, PI, and aroma and taste desirability of the breast muscles, as well as the aroma intensity of the leg muscles.

Genetic characteristics of waterfowl-origin H5N6 highly pathogenic avian influenza viruses and their pathogenesis in ducks and chickens

Waterfowl, such as ducks, are natural hosts for avian influenza viruses (AIVs) and act as a bridge for transmitting the virus to humans or susceptible chickens. Since 2013, chickens and ducks have been threatened by waterfowl-origin H5N6 subtype AIVs in China. Therefore, it is necessary to investigate the genetic evolution, transmission, and pathogenicity of these viruses. In this study, we determined the genetic characteristics, transmission, and pathogenicity of waterfowl-origin H5N6 viruses in southern China. The hemagglutinin (HA) genes of H5N6 viruses were classified into the MIX-like branch of clade 2.3.4.4h. The neuraminidase (NA) genes belonged to the Eurasian lineage. The PB1 genes were classified into MIX-like and VN 2014-like branches. The remaining five genes were clustered into the MIX-like branch. Therefore, these viruses belonged to different genotypes. The cleavage site of the HA proteins of these viruses was RERRRKR/G, a molecular characteristic of the H5 highly pathogenic AIV. The NA stalk of all H5N6 viruses contained 11 amino acid deletions at residues 58-68. All viruses contained 627E and 701D in the PB2 proteins, which were molecular characteristics of typical bird AIVs. Furthermore, this study showed that Q135 and S23 viruses could replicate systematically in chickens and ducks. They did not cause death in ducks but induced mild clinical signs in them. All the infected chickens showed severe clinical signs and died. These viruses were shed from the digestive and respiratory tracts and transmitted horizontally in chickens and ducks. Our results provide valuable information for preventing H5N6 avian influenza outbreaks.

Chimeric H5 influenza virus-like particle vaccine elicits broader cross-clade antibody responses in chickens than in ducks

Eurasian-lineage highly pathogenic avian influenza (HPAI) H5 viruses have spread throughout Asia, the Middle East, Europe, Africa, and most recently, North and South America. These viruses are independently evolving into genetically and antigenically divergent clades, and broad-spectrum vaccines protecting against these divergent clades are needed. In this study, we developed a chimeric virus-like particle (VLP) vaccine co-expressing hemagglutinins from two clades (clades 1 and 2.3.2.1) of HPAI H5 viruses and performed comparative cross-clade hemagglutination inhibition (HI) analysis in chickens and ducks. The chimeric VLP immunization induced a significantly broader spectrum of antibodies against various clades of HPAI H5 viruses than monovalent VLPs both in chickens and ducks. While the chimeric VLP led to broadened antibody responses in both species, significantly lower levels of HI antibodies were elicited in ducks than in chickens. Moreover, boost immunization failed to increase antibody responses in ducks regardless of the VLPs used, in contrast to chickens that showed significantly enhanced antibody responses upon boost immunization. These results suggest (1) the potential application of the chimeric VLP technology in poultry to help control HPAI H5 viruses by offering broader antibody responses against antigenically different strains and (2) possible obstacles in generating high levels of antibody responses against HPAI H5 viruses in ducks via vaccination, implying the need for advanced vaccination strategies for ducks.

Developmental Changes of Duckling Liver and Isolation of Primary Hepatocytes

The liver is the main site of fat synthesis and plays an important role in the study of fat deposition in poultry. In this study, we investigated the developmental changes of duckling livers and isolated primary duck hepatocytes. Firstly, we observed morphological changes in duckling livers from the embryonic period to the first week after hatching. Liver weight increased with age. Hematoxylin-eosin and Oil Red O staining analyses showed that hepatic lipids increased gradually during the embryonic period and declined post-hatching. Liver samples were collected from 21-day-old duck embryos for hepatocyte isolation. The hepatocytes showed limited self-renewal and proliferative ability and were maintained in culture for up to 7 days. Typical parenchymal morphology, with a characteristic polygonal shape, appeared after two days of culture. Periodic acid-Schiff (PAS) staining analysis confirmed the characteristics of duck embryo hepatocytes. PCR analysis showed that these cells from duck embryos expressed the liver cell markers ALB and CD36. Immunohistochemical staining and immunofluorescence analysis also confirmed ALB and CK18 expression. Our findings provide a novel insight regarding in vitro cell culture and the characteristics of hepatocytes from avian species, which could enable further studies concerning specific research on duck lipid metabolism.

Optimization of embryonic thermal programming confirms increased liver fattening in mule ducks and changes in lipid metabolism

Introduction: The embryonic thermal programming (TM) in birds has been shown to impact several physiological parameters such as resistance to thermal stress, muscle growth or immunity. In mule ducks, it has recently been shown that TM can induce metabolic programming resulting in increased liver weight and fat storage after overfeeding. However, a decrease in hatchability and foie gras quality was also observed, suggesting that this technique needs to be optimized. Here, we tested a new thermal manipulation condition determined with the objective of avoiding negative impacts while maintaining or improving liver properties. Methods: The eggs of the control group were incubated at 37.6°C during the whole incubation period while those of the experimental group (TM group) were incubated at 39.3°C 16 h/24 h from the 11^th day of incubation to the 21^st. After hatching, all the animals were fed and raised under the same conditions until the age of 12 weeks. At this stage, one part of the animals was overfed and then slaughtered 2 h (to measure rapid changes in metabolism) or 10 h after the last meal (to obtain the best technological yields), while the other part was ration-fed and slaughtered 2 h after the last meal, at the same age. Results: An 8% increase in foie gras production was measured in the TM group compared to the control group without altering the quality of the final product (nor hatchability), confirming the successful optimization of the metabolic programming. Interestingly, these results allowed us not to reject the previously suggested hypothesis of a potential delay in metabolic processes involved in liver fattening in programmed animals, in particular by measuring a trend reversal regarding the amount of total hepatic lipids in both groups at 2 h and then 10 h after the last meal. Discussion: This study therefore validates the optimization of metabolic programming by embryonic thermal manipulation for duck liver fattening. The understanding of the mechanisms of embryonic thermal programming in birds remains today very incomplete and the search for epigenetic marks (main hypothesis of the concept of programming) at the origin of the observed phenotypes could be the next step of this work.

Domestication affects sex-biased gene expression evolution in the duck

Genes with sex-biased expression are thought to underlie sexually dimorphic phenotypes and are therefore subject to different selection pressures in males and females. Many authors have proposed that sexual conflict leads to the evolution of sex-biased expression, which allows males and females to reach separate phenotypic and fitness optima. The selection pressures associated with domestication may cause changes in population architectures and mating systems, which in turn can alter their direction and strength. We compared sex-biased expression and genetic signatures in wild and domestic ducks (Anas platyrhynchos), and observed changes of sexual selection and identified the genomic divergence affected by selection forces. The extent of sex-biased expression in both sexes is positively correlated with the level of both d _N /d _S and nucleotide diversity. This observed changing pattern may mainly be owing to relaxed genetic constraints. We also demonstrate a clear link between domestication and sex-biased evolutionary rate in a comparative framework. Decreased polymorphism and evolutionary rate in domesticated populations generally matched life-history phenotypes known to experience artificial selection. Taken together, our work suggests the important implications of domestication in sex-biased evolution and the roles of artificial selection and sexual selection for shaping the diversity and evolutionary rate of the genome.

Migratory connectivity of North American waterfowl across administrative flyways

Management of waterfowl that migrate seasonally across North America occurs within four flyways that were delineated in the early 1900s to include the annual movements of populations. Movements may have changed over the past century since the administrative flyways were established, and may do so while management plans are in use, so information about transitions among flyways through time can illustrate how management assumptions may change. Today there are more than 12 million records from 60 years of migratory waterfowl band recoveries to assess adaptive management approaches that will be most effective when they account for movements within and between flyways. We examined how much the movement of North American waterfowl occurs between flyways, whether those movements have changed through time, and whether movements of mallards are representative of multiple species, as suggested by current harvest management strategies. We estimated the probability a duck would transition from one flyway to another and the strength of migratory connectivity (MC) for each species within and among flyways. We used capture-mark-recovery models to estimate population-specific movement within and among flyways (transition probabilities) for 15 migratory waterfowl species that were banded during breeding and recovered during winter. We developed new functionality in the R package MigConnectivity to estimate the species-specific strength of MC using transition probability samples from the capture-mark-recovery models. We found the regular movement of duck populations among flyways, overall weak MC, and no consistent change in migratory movements through time. Mallard movements were median among all duck species, but significantly different from many species, particularly diving ducks. Despite the significant movement between flyways, our work suggests flyway management of waterfowl matches many of the seasonal movements of these species when considering mid-continent flyway management. We recommend models accounting for all transition probabilities between populations and regularly estimating harvest derivations, transition probabilities, and MC metrics to verify that the current movements match model assumptions.

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.

Prediction of the Net Energy of Wheat from Chemical Analysis for Growing Ducks

The goal of this study was to determine the net energy (NE) value of wheat for growing ducks and establish a NE prediction equation based on the grain's chemical composition. Forty wheat samples were selected based on bulk weight from major wheat-producing regions in China. A total of 460 1-week-old ducks (initial body weight (BW): 134.86 ± 3.32 g) were randomly assigned to 46 diets, including a basal diet, 5 restricted feeding diets and 40 test diets. Each diet contained five replicates, each with two ducks. The basic diet was a corn-soybean meal, and 40 kinds of experimental diets were prepared by mixing the basic diet with 20% wheat. A prediction equation for the NE concentration was created using the chemical make-up of wheat samples. The results indicated that the NE and apparent metabolism energy (AME) content of 40 wheat samples ranged from 6.81 to 9.12 MJ/kg and from 11.03 to 14.34 MJ/kg, respectively. The ether extract (EE), neutral detergent fiber (NDF), acid detergent fiber (ADF) and AME were highly correlated with NE value (p < 0.01), with the AME and NE showing the strongest correlation (r = 0.884). Chemical features could be used to predict the NE values with accuracy, and the prediction equation was strengthened by the inclusion of the AME. The best-fit equation was as follows: NE = 0.380 AME - 0.147 NDF - 0.274 ADF + 5.262 (R² = 0.874, RSD = 0.19, p < 0.001). In summary, the NE value of wheat is 8.49 ± 0.30 MJ/kg for growing ducks, and the chemical composition can be used to accurately predict NE in wheat.

Conserved Expression and Functionality of Furin between Chickens and Ducks as an Activating Protease of Highly Pathogenic Avian Influenza Virus Hemagglutinins

Highly pathogenic avian influenza viruses (HPAIVs) typically emerge from low-pathogenic avian influenza viruses (LPAIVs) of the H5 and H7 subtypes upon spillover from wild aquatic birds into poultry. The conversion from LPAIV to HPAIV is characterized by the acquisition of a multibasic cleavage site (MBCS) at the proteolytic cleavage site in the viral binding and fusion protein, hemagglutinin (HA), resulting in cleavage and activation of HA by ubiquitously expressed furin-like proteases. The ensuing HPAIVs disseminate systemically in gallinaceous poultry, are endotheliotropic, and cause hemorrhagic disease with high mortality. HPAIV infections in wild aquatic birds are generally milder, often asymptomatic, and generally not associated with systemic dissemination nor endotheliotropic. As MBCS cleavage by host proteases is the main virulence determinant of HPAIVs in poultry, we set out to determine whether cleavage of HPAIV HA by host proteases might influence the observed species-specific pathogenesis and tropism. Here, we sequenced, cloned, and characterized the expression and functionality of duck furin. The furin sequence was strongly conserved between chickens and ducks, and duck furin cleaved HPAIV and tetrabasic HA in an overexpression system, confirming its functionality. Furin was expressed ubiquitously and to similar extents in duck and chicken tissues, including in primary duck endothelial cells, which sustained multicycle replication of H5N1 HPAIV but not LPAIVs. In conclusion, differences in furin-like protease biology between wild aquatic birds and gallinaceous poultry are unlikely to largely determine the stark differences observed in species-specific pathogenesis of HPAIVs. IMPORTANCE HPAIV outbreaks are a global concern due to the health risks for poultry, wildlife, and humans and their major economic impact. The number of LPAIV-to-HPAIV conversions, which is associated with spillover from wild birds to poultry, has been increasing over recent decades. Furthermore, H5 HPAIVs from the A/goose/Guangdong/1/96 lineage have been circulating in migratory birds, causing increasingly frequent epizootics in poultry and wild birds. Milder symptoms in migratory birds allow for dispersion of HPAIVs over long distances, justifying the importance of understanding the pathogenesis of HPAIVs in wild birds. Here, we examined whether host proteases are a likely candidate to explain some differences in the degree of HPAIV systemic dissemination between avian species. This is the first report to show that furin function and expression is comparable between chickens and ducks, which renders the hypothesis unlikely that furin-like protease differences influence the HPAIV species-specific pathogenesis and tropism.

Effects of testis testosterone deficiency on gene expression in the adrenal gland and skeletal muscle of ducks

1. Testosterone has an anabolic effect on skeletal muscle. The testes produce most of the testosterone in vivo, while the adrenal glands contribute smaller amounts. When testis testosterone is deficient the adrenal gland increases steroid hormone synthesis, which is referred to as compensatory testicular adaptation (CTA).2. To reveal the effects of testis testosterone deficiency on adrenal steroid hormones synthesis and skeletal muscle development, gene expression related to adrenal steroid hormones synthesis and skeletal muscle development were determined by RNA-seq.3. The results showed that castrating male ducks had significant effects on their body weight but no significant impact on cross-sectional area (CSA) or density of pectoral muscle fibres. In skeletal muscle protein metabolism, expression levels of the catabolic gene atrogin1/MAFbx and the anabolic gene eEF2 were significantly higher, with concomitant increases after castration. The adrenal glands' alteration of the steroid hormone 11β-hydroxylase (CYP11B1) was significantly lower following castration.4. Expression pattern analysis showed that the adrenal glands' glucocorticoid receptor (NR3C1/GR) had a potential regulatory relationship with the skeletal muscle-related genes (Pax7, mTOR, FBXO32, FOXO3, and FOXO4).5. The data showed that castration affected muscle protein metabolism, adrenal steroid and testosterone synthesis. In addition, it was speculated that, after castration, steroid hormones produced by the adrenal gland could have a compensatory effect, which might mediate the changes in skeletal muscle protein metabolism and development.

Treatment of Septic Tenosynovitis and Osteoarthritis in an American White Pekin (Anas platyrhynchos domesticus) with Repeated Intravenous Regional Limb Perfusion and Antibiotic-Impregnated Calcium Sulfate Beads

A 2-year-old female American white pekin (Anas platyrhynchos domesticus) was assessed for a 2-month history of chronic lameness and swelling involving the left leg. Radiographic images of the left leg showed soft tissue swelling of the digits and tarsometatarsus with osteolysis of the tarsometatarsal-phalangeal joint. A complete blood count revealed marked leukocytosis and hyperproteinemia. A Streptococcus species was isolated from a bacterial culture of fluid obtained from the left tarsometatarsal-phalangeal joint. Biweekly intravenous regional limb perfusions of the left leg with ampicillin-sulbactam and amikacin were performed on the patient. Despite initial improvement in left leg lameness and swelling, follow-up radiographic images showed progressive osteolysis of the tarsometatarsal-phalangeal joint and associated digits. Surgical placement of antibiotic-impregnated calcium sulfate beads into the left tarsometatarsal-phalangeal joint was next performed with concurrent, repeated intravenous regional limb perfusion using the same antibiotic. Following the placement of antibiotic-impregnated beads and continued intravenous regional limb perfusion, the duck had decreased lameness and swelling of the left leg. Repeated antibiotic treatment through intravenous regional limb perfusion and concurrent placement of antibiotic-impregnated calcium sulfate beads is a practical treatment option for complicated distal limb infections in avian species. This therapeutic protocol has great potential in treating aggressive distal leg infections in many avian species because regional limb perfusion alone may not penetrate the joint adequately to achieve complete resolution of infection.