Identification and genomic analysis of two novel duck-origin GPV-related parvovirus in China.

BACKGROUND: Since early 2015, mule duck and Cherry Valley duck flocks have been suffering from short beak and dwarfism syndrome. This widely spreading infectious disease is characterized by growth retardation, smaller beak and tarsus with high morbidity and low mortality rate. For better understanding, we identified and characterized virus isolates named AH and GD from diseased Cherry Valley duck and mule duck flocks and investigated the damage caused by novel parvovirus-related virus (NGPV) to tissues and organs, including kidney, brain, pancreas, liver, spleen, bursa of fabricius and myocardial tissues. RESULTS: AH and GD isolates shared high nucleotide identity with goose parvovirus (GPV). Alignment studies of AH and GD isolates showed 94.5-99.2% identity with novel parvovirus-related virus (NGPV), 98.7-91.5% identity with GPV and 79.9-83.7% with muscovy duck parvovirus (MDPV). Compared with other NGPV, classical GPV and MDPV sequences, a four 14-nucleotide-pair insertion in GD isolate was found in left open reading frame (ORF) (87-100 nt and 350-363 nt) and in right ORF (4847-4861 nt and 5122-5135 nt). However, in AH isolate, a five 14-nucleotide-pair deletions similar to other NGPV were found. The complete genome sequence comparison of eleven NGPV isolates from mule ducks and cherry valley ducks revealed no remarkable difference between them. Notably, the myocardium and bursa of fabricius of both disease and healthy animals are perfectly normal while other tissues have inflammatory cells exudation. CONCLUSIONS: The AH and GD strains are novel parvovirus-related virus that isolates from mule ducks or cherry valley ducks which DNA sequence has no remarkable difference. The histopathology of tissues and organs such as kidney, brain etc. revealed non-significant changes in experimental and control animals. Overall, this study has contributed better understanding of molecular biology of NGPV strains and will help to develop the candidate strain for vaccine preparation to get better protection against these viral infections.

Lactobacillus acidophilus and Bacillus subtilis significantly change the growth performance, serum immunity and cecal microbiota of Cherry Valley ducks during the fattening period.

This study explored the effects of a Bacillus subtilis and Lactobacillus acidophilus mixture containing the co-fermented products of the two probiotics on growth performance, serum immunity and cecal microbiota of Cherry Valley ducks. This study included 480 one-day-old Cherry Valley ducks divided into four feeding groups: basal diet (control group) and basal diet supplemented with 300, 500, or 700 mg/kg of the probiotic powder; the ducks were raised for 42 days. Compared with the control group, body weight on day 42 and the average daily gain on days 15-42 significantly increased (p < 0.05), and the feed conversion rate significantly decreased (p < 0.05) in the experimental groups. Furthermore, the serum immunoglobulin (Ig) A, IgG, IgM, and interleukin (IL)-4 levels increased significantly (p < 0.05), and IL-1ß, IL-2, and tumor necrosis factor-α decreased significantly (p < 0.05) in the experimental groups. Finally, Sellimonas, Prevotellaceae NK3B31 group, Lachnospiraceae NK4A136 group and Butyricoccus played an important role in the cecal microbiota of the experimental group. Thus, the probiotic powder has impacts on the growth performance, serum immunity and cecal microbiota of Cherry Valley Ducks.

Effects of potassium diformate on growth performance, apparent digestibility of nutrients, serum biochemical indices, and intestinal microflora in Cherry Valley ducks.

This study was performed to investigate the effects of potassium diformate (KDF) on growth performance, apparent digestibility of nutrients, serum biochemical indices, and intestinal microflora of Cherry Valley ducks. In total, 144 female healthy 1-day-old Cherry Valley ducks were divided into 3 groups with 6 replicates per group and 8 ducks per replicate according to the principle of similar body weight. The control group was fed a basic diet. In the 2 experimental groups, 0.8% and 1.2% KDF was added to the basic diet, respectively. The trial period was 6 wk and the pretrial period was 3 wk. The final weight and ADG were significantly higher in the 0.8% KDF group than in the control group (P < 0.05). The feed-to-gain ratio was significantly lower in both KDF groups than in the control group (P < 0.05). The apparent digestibility of CP was significantly higher in both KDF groups than in the control group (P < 0.05). The apparent digestibility of calcium was also significantly higher in the 0.8% KDF group (P < 0.05). The serum levels of alkaline phosphatase, cholesterol, and total protein were significantly lower in the 0.8% KDF group than in the control group (P < 0.05), the IgM content was significantly higher (P < 0.05), the low-density lipoprotein cholesterol, triglyceride, and urea levels were significantly lower (P < 0.01), and the glucose level was significantly higher (P < 0.01). The serum total protein level was significantly higher in the 1.2% KDF group than in the control group (P < 0.05). The relative abundance of Firmicutes and Patescibacteria in the gut of ducks was significantly higher in the 0.8% KDF group than in the control group (P < 0.05), the relative abundance of unclassified Erysipelotrichaceae and Lactobacillus was significantly higher (P < 0.01), and the relative abundance of Fusobacteriota was significantly lower (P < 0.05). However, the relative abundance of Firmicutes in the gut of ducks was significantly higher in the 1.2% KDF group than in the control group (P < 0.05). The relative abundance of unclassified Erysipelotrichaceae and Clostridium sensu stricto 1 was significantly higher (P < 0.01), as was the relative abundance of Fusobacteriota and Proteobacteria (P < 0.05). These findings indicate that the addition of 0.8% KDF to the diet can improve the growth performance of Cherry Valley ducks, promote the absorption of nutrients, change the structure of the microflora in the cecum, and increase the relative abundance of dominant bacteria. It was also shown that there was a significant difference between the 0.8% and 1.2% KDF levels which suggest that the safety margin for overdosing is quite low.

Effects of feeding silage of beet pulp or maize on the growth performance, meat quality, and production economics of broiler ducks.

The present study aimed to compare the growth, meat quality, and production economics of Cherry Valley broiler ducks fed with a commercial diet along with silage from beet pulp or maize. In this study, 180 male Cherry Valley ducks were reared for 49 d. The control group (group C) was fed a commercial diet ad libitum. The experimental groups were fed a restricted amount of commercial diet and ad libitum beet pulp silage (group B) or maize silage (group M). For all groups, the growth performance and meat quality were analyzed, and their production costs were estimated. The beneficial effects of feeding maize silage on the growth rate were observed on d 29 to 49 in group M; moreover, both experimental groups showed lower feed intake than group C (P < 0.05). The feed conversion ratio was lower in the first rearing stage and during the entire experimental period in groups B and M than that in group C. Group M showed a higher European Production Efficiency Factor and European Broiler Index than group C (P < 0.05). The relative weight of the liver was higher in group C than that in the experimental groups (P < 0.05). Group M showed a higher L* value of leg muscles than group C (P < 0.05). Water-holding capacity was higher in leg muscles from ducks fed with silages (P < 0.05). The experimental groups had lower costs of commercial diets. Higher costs were observed for maize silage than for beet pulp silage. Carcass sales yielded the highest profit for group M and the lowest one for group C. Compared with the control group, the silage-fed groups showed a higher estimated profit by PLN 7.94 to 10.68 per duck (P < 0.05). Based on the beneficial production results, notably lower feed conversion ratio, no negative effects on carcass characteristics, and lower production costs, especially maize or even beet pulp silage in broiler duck rearing, could be recommended.

Genome cloning and genetic evolution analysis of eight duck-sourced novel goose parvovirus strains in China in 2023.

Introduction: There are three major categories of waterfowl parvoviruses, namely goose parvovirus (GPV), Muscovy duck parvovirus, and novel goose parvovirus (NGPV). NGPV can infect both Cherry Valley ducks and mule ducks, resulting in short beaks and dwarfism syndrome, and the incidence of short beaks and dwarfism syndrome rises annually, posing a significant threat to the waterfowl breeding and the animal husbandry. Therefore, clarifying the biological characteristics and genetic evolution of NGPV is very important for the prevention and control of NGPV. Methods: Ducks with short beaks and dwarfism syndrome from Shandong and Henan Province were investigated by dissection and the tissue samples were collected for study. The NGPV genome was amplified by PCR, and the genome was analyzed for genetic evolution. Results: Eight strains of NGPV were isolated, which were designated as HZ0512, HZ0527, HZ0714, HZ0723, HZ0726, HZ0811, HZ0815, and HN0403. The nucleotide homology among these strains ranged from 99.9% to 100%. The eight strains, along with other NGPVs, belong to GPV. The eight strains showed a 92.5%-98.9% nucleotide homology with the classical GPV, while a 96.0%-99.9% homology with NGPV.Therefore, it can be deduced that there have been no major mutations of NGPV in Shandong and Henan provinces in recent years. Discussion: This study lays a theoretical foundation for further studying the genetic evolution and pathogenicity of NGPV, thereby facilitating the prevention and control of NGPV.

Research Note: Complete genome cloning and genetic evolution analysis of four Cherry Valley duck circovirus strains in China in 2022.

In recent years, with the expansion of duck breeding industry in China, the infection rate of duck circovirus (DuCV) in duck and the mixed infection rate of DuCV with other diseases increased significantly, which seriously endanger the development of duck breeding industry. To study the epidemic status of duck circovirus in China, analyze the virus's genetics and evolution, and establish a foundation for scientific prevention and control of duck circovirus, our laboratory collected 4 disease materials preliminarily diagnosed as duck circovirus infections. Conventional PCR was used to amplify 4 strains of duck circovirus with a full length of 1993bp, and their sequences were compared and analyzed. The analysis showed that the 4 DuCVs had typical circovirus characteristics, including 3 major ORFs: ORFV1 (Rep protein), ORFC1 (Cap protein), ORFC2 (apoptosis-related protein), and a stem ring structure. The 4 strains were compared with 22 other reference strains, and the results revealed that all 4 strains belonged to the DuCV-I type represented by the German strain AY228555. Furthermore, the homology between the 4 DuCVs and the reference strains was up to 98.6%, which help us to understand the genotype and genetic variation of DuCV in these regions and provide a reference for the prevention and control of DuCV.

Dietary supplementation of ferrous glycinate improves intestinal barrier function by modulating microbiota composition in Cherry Valley ducks.

Ferrous glycinate (Fe-Gly) has been increasingly used as iron fortification in the diets of weaned piglets and broilers, but the effect of Fe-Gly on intestinal barrier function in meat ducks has not been well defined. This study therefore investigated the effect of Fe-Gly on apparent nutrient utilization, hematological indices, intestinal morphological parameters, intestinal barrier function and microbial composition in meat ducks. A total of 672 one-day-old Cherry Valley ducks were randomly divided into 6 treatments (8 replicates for each treatment and 14 ducks for each replicate) and fed diets with 0 (control), 30, 60, 90 and 120 mg/kg Fe-Gly or 120 mg/kg FeSO4 for 35 d. The results showed that diets supplemented with Fe-Gly significantly increased average daily gain (ADG), average daily feed intake (ADFI), hematocrit (HCT), mean cell volume (MCV), the apparent utilization of dry matter (DM) and metabolizable energy (ME), villus height (VH) and villus height-to-crypt depth ratio (V:C) (P < 0.05). Fe-Gly also significantly up-regulated barrier-related genes including zonula occludens-1 (ZO-1), zonula occludens-2 (ZO-2), mucin 2 (MUC2) and lysozyme (LYZ) (P < 0.05), and down-regulated the mRNA expression of claudin-2 (CLDN2) and occludin (OCLN) in the jejunum (P < 0.05). The 16S rRNA sequence analysis indicated that the diet with Fe-Gly had a higher relative abundance of Intestinimonas and Romboutsia (P < 0.05), which have an ability to produce short chain fatty acids (SCFAs), especially butyric acid. It also decreased the relative abundance of pathobiont, including Megamonas, Eubacterium_coprostanoligenes_group and Plebeius (P < 0.05). Additionally, diets supplemented with 120 mg/kg Fe-Gly significantly increased the apparent utilization of DM and ME (P < 0.05) and decreased the relative abundance of Megamonas_unclassified and Bacteroides_unclassified compared with those fed 120 mg/kg FeSO4 (P < 0.05). These results revealed that diets supplemented with Fe-Gly exerted a potent beneficial effect on physical, chemical, immune and microbial barriers, thereby improving the integrity of the intestinal structure, promoting the digestion and absorption of nutrients to a certain extent, and ultimately elevating the growth performance of ducks.

Identification and antiviral effect of Cherry Valley duck IRF4.

Interferon regulatory factor 4 (IRF4) is a multifunctional transcription factor that plays an important regulatory role in the interferon (IFN) signaling. IRF4 participates in the process of antivirus, Th cell differentiation and B cell maturation by regulating the expression of IFN and some lymphokines. In this study, Cherry Valley duck IRF4 (duIRF4) was cloned and its cDNA was analyzed. Expression of duIRF4 in a wide variety of tissues and changes in duIRF4 expression due to viral infection also was detected by quantitative real-time PCR. The results show that duIRF4 contains 1,341 bp of ORF encoding a protein with 446 amino acids and contains 3 domains: DNA-binding domain (DBD), IRF-association domain (IAD) and nuclear localization signal (NLS). Quantitative real-time PCR analysis showed that duIRF4 was evenly expressed in all tissues examined, with the highest expression in the spleen, followed by the bursa of Fabricius, and lower in the skin and brain. In addition, expression of duIRF4 in the brain and spleen was significantly upregulated after being infected by duck plague virus, duck Tembusu virus, and novel duck reovirus. These data suggest that duIRF4 may be involved in innate immune response.

Structure and expression identification of Cherry Valley duck IRF8.

Interferon regulatory factor 8 (IRF8) is also known as interferon (IFN) consensus sequence binding protein (ICSBP), which plays an important role in IFN signal transduction. In this study, we cloned the full-length coding sequence of Cherry Valley duck IRF8 (duIRF8) and analyzed its structure. In addition, we tested the distribution of IRF8 in the tissues of healthy Cherry Valley ducks, and the changes in IRF8 expression levels in the tissues after virus infection. The results show that the open reading frame (ORF) of IRF8 is 1293 bp, encodes 430 amino acids, and have 3 conserved domains: the N-terminal DBD domain, the C-terminal IAD domain, and the NLS domain. Besides, from the analysis of the phylogenetic tree, it can be known that the duIRF8 has the highest homology with the anser cygnoides, and has less homology with the fish. Analyzing the distribution level of IRF8 in the tissues, it is found that the expression level of IRF8 in the liver of Cherry Valley duck is the highest. However, after infection with duck Tambusu virus, novel duck reovirus, and duck plague virus, the expression of IRF8 in the spleen and brain all showed up-regulation. These data indicate that IRF8 is involved in the host's innate immune response against virus in Cherry Valley duck.

The replacement of bacitracin methylene disalicylate with Bacillus subtilis PB6 in the diet of male Cherry Valley Ducks reduces the feed conversion ratio by improving intestinal health and modulating gut microbiota.

In this study, we compared the impacts of Bacillus subtilis PB6 (BS) and bacitracin methylene disalicylate (BMD) on the growth performance, intestinal morphology, expression of tight connection protein, and cecal microbiota community of male ducks through a 42-d trial. Three-hundred and sixty male Cherry Valley meat-type ducklings (1-day-old) were distributed into 3 groups of 6 replicates: CON group (control, basal diet), BMD group (basal diet + 45 mg/kg BMD, active ingredient dose in the feed), and BS group (basal diet + 2 × 107 CFU/kg BS in the feed). Results showed that supplementing the diet with BS reduced the average daily feed intake (ADFI) during d 15 to 42 and d 1 to 42 compared with the CON group (P = 0.032). It also reduced feed conversion ratio (FCR) during d 15 to 42 and d 1 to 42 (P < 0.05) relative to the other groups. The ileal villus height (VH) and villus height /crypt depth ratio (V/C) were increased (P < 0.05) in both the BS and BMD groups, and the jejunal VH and V/C ratio were increased in the BS group (P < 0.05). Relative to the CON, BS supplementation was associated with numerical augmentation of goblet cells in the jejunal mucosa and upregulation of jejunal zonula occludens (ZO-1) and ileal mucin2 (P < 0.05) mRNA levels. Analysis showed a negative correlation between FCR (d 0-42) and VH, V/C, and the number of goblet cells in the jejunum (P < 0.05). Additionally, BMD or BS supplementation altered the alpha diversity of colonic microbiota (P < 0.05). Correlation analysis revealed that Butyricimonas, Enterobacteriaceae, Clostridiaceae, and Tannerellaceae were positively associated with the acetic acid and butyrate concentrations (P < 0.05). Taken together, the supplementation of BS in the diet of male ducks was conducive to reducing FCR by meliorating intestinal morphology, upregulating ZO-1 and mucin2 mRNA levels, regulating the abundance of microbiota, and metabolites, and having a greater effect than BMD supplementation.

Mineral Element Deposition and Gene Expression across Different Tissues of Cherry Valley Ducks.

This study was conducted to investigate the deposition of several mineral elements and the mRNA levels of mineral-related genes across different tissues of cherry valley ducks. The contents of magnesium (Mg), potassium (K), zinc (Zn), and selenium (Se) in ducks' breast muscle, thigh muscle, liver, skin, and tibia at the age of 0, 21, 35, 49, and 63 days, respectively, were measured using an atomic fluorescence spectrophotometer, while the mRNA levels of mineral-related genes were detected by qRT-PCR. The results revealed that the dynamics of Mg and K were generally similar in each tissue, with a significant positive correlation (p < 0.05). In the breast muscle, thigh muscle, and liver, the contents of almost all mineral elements reached their peak values (p < 0.05) at the age of 49 to 63 days. Interestingly, the expression of most mineral-related genes was the highest at birth (p < 0.05). In addition, there was a significant negative correlation between the expression of ATP1A1 and the deposition of K (r = -0.957, p < 0.05), and a similar result was found for the expression of ATP8 and the deposition of Zn (r = -0.905, p < 0.05). Taken together, Mg and K could be used as joint indicators for the precise breeding of the high-quality strain of cherry valley ducks, while the age of 49 to 63 days could be used as the reference for the best marketing age. In addition, ATP1A1 and ATP8 could be used as the key genes to detect K and Zn, respectively. Hence, the findings of this study can be used to improve the production and breeding efficiency of high-quality meat ducks.

Identification, cloning, and characterization of Cherry Valley duck CD4 and its antiviral immune responses.

CD4 protein is a single chain transmembrane glycoprotein and has a broad functionality beyond cell-mediated immunity. In this study, we cloned the full-length coding sequence (CDS) of duck CD4 (duCD4) and analyzed its sequence and structure, and expression levels in several tissues. It consists of 1,449 nucleotides and encodes a 482 amino acid protein. The putative protein of duCD4 consisted of an N-terminal signal peptide, three immunoglobulins and one immunoglobulins-like domain in its central, one terminal transmembrane region, and a C-terminal domain of the CD4 T cell receptor. The duCD4 also has the typical signature "CXC" of CD4s. The multiple sequence alignment suggests duCD4 has four potential N-glycosylation sites and the phylogenetic analysis suggests duCD4 shares greater similarity with avian than other vertebrates. Quantitative real-time PCR analysis showed that duCD4 mRNA transcripts are widely distributed in the healthy Cherry Valley duck, and the highest level in the thymus. During the virus infection, the obvious change of duCD4 expression was observed in the spleen, lung and brain, which suggesting that duCD4 could be involved in the host's immune response to multiple types of viruses. Our research studied the characterization, tissue distribution, and antiviral immune responses of duCD4.

Cloning, analysis, and anti-duck Tembusu virus innate immune response of Cherry Valley duck tripartite motif-containing 32.

Tripartite motif-containing 32 (TRIM32) is an E3 ubiquitin ligase with multiple functions. In this study, we amplified TRIM32 gene from the Cherry Valley duck, and its cDNA sequence contained an open reading frame of 1,950 bp that encodes 649 amino acids. Duck TRIM32 (duTRIM32) mRNA was expressed in all tissues tested. A series of immune-related genes that were induced by viral infection, including interferon alfa, IL-1ß, retinoic acid-inducible gene-I, Mx, and OAS, were regulated by duTRIM32 expression. DuTRIM32 overexpression inhibits duck Tembusu virus (DTMUV) replication in the early stages of viral infection. Knockdown of duTRIM32 expression by siRNA reduced the ability of duck embryo fibroblast cells to mount a type Ⅰ interferon response to DTMUV. Therefore, our results suggest that the duTRIM32-mediated signal pathway plays an essential role in DTMUV infection-induced innate immune response.

Cherry Valley Duck Galectin-2 Plays an Essential Role in Avian Pathogenic Escherichia coli Infection-Induced Innate Immune Response.

Galectins play important roles in the host's innate immunity as pattern recognition receptors. In this study, the coding sequences of galectin-2 were identified from Cherry Valley ducks. Tissue distribution of duck galectin-2 (duGal-2) in healthy ducks and ducks infected with avian pathogenic Escherichia coli (APEC) was studied, respectively. The results showed that duGal-2 expression was higher in the gut, kidney, and liver tissue, and weakly expressed in the lung and brain, in healthy ducks; however, the expression level of duGal-2 was detected as being up-regulated after infection with APEC. In addition, knockdown or overexpression of duGal-2 in DEFs was achieved by small interference RNA (siRNA) transfection and plasmid transduction, respectively. The knockdown of duGal-2 led to a decrease in the expression of some inflammatory cytokines such as IL-1ß, IL-6, and IL-8, while the expression levels of anti-inflammatory factor IL-10 were up-regulated. At the same time, the bacterial load of APEC was increased after knockdown of duGal-2 in vitro. However, the opposite results were obtained in the duGal-2 overexpression group. Taken together, duGal-2 plays an important role in the host against APEC infection.

Proteomic responses to oxidative damage in meat from ducks exposed to heat stress.

Heat stress causes oxidative damage and quality reduction in poultry. Here, a tandem mass tag proteomic approach was applied to investigate the proteomic differences in duck meat from birds exposed to heat stress. Altogether 212 differential proteins were identified, including 178 down-regulated and 34 up-regulated proteins, compared to the control. Malondialdehyde and carbonyl content and cooking loss of the chest muscle significantly increased under heat stress. The proteomic analysis indicated that heat stress suppressed mitochondrial functions and respiratory chains, which might be responsible for the higher oxidation level. The results also revealed potential protective proteins involved in the defensive mechanisms against heat stress in duck muscles, such as sarcoplasmic/endoplasmic reticulum calcium ATPases, Mn-superoxide dismutase, heat shock protein family B member 7, methyltransferase like 21C, myosin-binding protein C, and carbonic anhydrase 3. These results provide potential targets for the research and identification of oxidative meat products due to heat stress.

Investigation of the relationships between different enzymes and postmortem duck muscle tenderization.

Postmortem tenderization is induced by the cooperation of various related enzymes. In this study, CaCl2 and MDL-28170 (Cbz-Val-Phe-H, a calpain inhibitor) were used to regulate the postmortem tenderization process of duck breast muscle. Then the relationship between muscle tenderness change and different enzymes was investigated. At day 0, day 1, and day 4 of the postmortem ageing, the shear force, myofibril fragmentation index (MFI), enzymatic activities of calpains, cathepsin-B, caspase-3, Na+/K+-ATPase, and Ca2+-ATPase were respectively determined. The results showed that duck muscle tenderness could be significantly raised by CaCl2 and reduced by MDL-28170, respectively (P < 0.05). The CaCl2 treatment did not promote the calpains activity as predicted (P > 0.05), but significantly up-regulated the activity of cathepsin-B (P < 0.05). The MDL-28170 significantly inhibited the activity of the calpain system at day 1 (P < 0.05) and raised the activities of the selected 3 apoptosis-related enzymes, including caspase-3, Na+/K+-ATPase, and Ca2+-ATPase, at both day 1 and day 4 (P < 0.05). These data indicated that in duck, the calpain system could be well activated after death, and cathepsin-B might also play an important role in postmortem muscle tenderization. The caspase-3, Na+/K+-ATPase, and Ca2+-ATPase probably have no significant effects on duck muscle tenderness. It might provide useful information for duck production and further research on postmortem muscle tenderization.

Detection and Molecular Characterization of Two Genotypes of Goose Parvoviruses Isolated from Growing Period Geese and Cherry Valley Ducks in China.

Goose parvovirus (GPV) is the etiologic pathogen of Derzsy's disease, causing great economic losses in the waterfowl industry. A novel GPV-related virus (NGPV), which caused short beak and dwarfism syndrome, has occurred in China since 2015. In this study, two GPV strains (RC45 and RC70) were isolated from diseased growing period geese (45 days old and 70 days old), and one NGPV strain GXN45 was isolated from a 45-day-old Cherry Valley duck in China. To better understand the genetic diversity between GPVs isolated from growing period waterfowls and other classical waterfowl parvoviruses, the complete genomes and main genes were sequenced and analyzed. Full-length genomic sequence alignments demonstrated that both RC45 and RC70 showed the highest identity with classical GPVs YZ99-6 and SHFX1201, whereas GXN45 shared the highest identity with NGPV SDLC01. Sequence alignment of the inverted terminal repeat region showed that GXN45, RC45, and RC70 had two 14-nucleotide (nt) deletions compared with the classical GPV virulent B strain and one 14-nt deletion compared with mule duck-origin NGPV M15 strain. Phylogenetic tree analysis of nonstructural and VP1 genes showed that GXN45 was clustered into a branch with NGPV QH15 strain except for the VP1 amino acid tree. Although both RC45 and RC70 formed one separate branch distinct from classic GPV isolates, they were in one large phylogenetic tree branch. This study will contribute to a better understanding of the genetic diversity and molecular characterization of three isolated parvoviruses and lay the foundation to further study the relationship between mutations of virus genome and viral pathogenicity.

Detección y caracterización molecular de dos genotipos del parvovirus del ganso aislados de gansos en período de crecimiento y de patos Cherry Valley en China. El parvovirus del ganso (GPV) es el patógeno etiológico de la enfermedad de Derzsy, que causa grandes pérdidas económicas en la industria de las aves acuáticas. Un nuevo virus relacionado con el parvovirus del ganso (NGPV), que causó el síndrome de pico corto y enanismo, se ha presentado en China desde el año 2015. En este estudio, se aislaron dos cepas de parvovirus del ganso (RC45 y RC70) a partir de gansos enfermos en período de crecimiento (45 días de edad y 70 días) y se aisló una cepa del nuevo virus relacionado con el parvovirus del ganso, cepa GXN45 a partir de un pato Cherry Valley de 45 días de edad en China. Para comprender mejor la diversidad genética entre los aislamientos del parvovirus del ganso de aves acuáticas en período de crecimiento y de otros parvovirus clásicos de aves acuáticas, se secuenciaron y analizaron los genomas completos y los genes principales. Las alineaciones de secuencias genómicas completas demostraron que tanto RC45 como RC70 mostraron la identidad más alta con los parvovirus de ganso clásicos cepas YZ99-6 y SHFX1201, mientras que la cepa GXN45 compartió la identidad más alta con nuevo virus relacionado con el parvovirus del ganso cepa SDLC01. La alineación de la secuencia de la región repetida invertida terminal mostró que las cepas GXN45, RC45 y RC70 tenían dos deleciones de 14 nucleótidos (nt) en comparación con la cepa B clásica virulenta del parvovirus del ganso y una deleción de 14 nucleótidos en comparación con la cepa M15 de un virus nuevo relacionado con el parvovirus del ganso originado en patos mula. El análisis del árbol filogenético de los genes no estructurales y VP1 mostró que la cepa GXN45 se agrupó en una rama con la cepa QH15 del nuevo virus relacionado con el parvovirus del ganso, excepto en el árbol de aminoácidos de VP1. Aunque tanto RC45 como RC70 formaron una rama separada distinta de los aislados de parvovirus de ganso clásicos, estaban en una rama de árbol filogenética grande. Este estudio contribuirá a una mejor comprensión de la diversidad genética y en la caracterización molecular de tres aislamientos de parvovirus aislados y contribuirá con las bases para seguir estudiando la relación entre las mutaciones del genoma del virus y la patogenicidad viral.

Associations of Gut Microbiota With Heat Stress-Induced Changes of Growth, Fat Deposition, Intestinal Morphology, and Antioxidant Capacity in Ducks.

Accumulating evidence has revealed the dysbiosis of gut/fecal microbiota induced by heat stress (HS) in mammals and poultry. However, the effects of HS on microbiota communities in different intestinal segments of Cherry-Valley ducks (a widely used meat-type breed) and their potential associations with growth performances, fat deposition, intestinal morphology, and antioxidant capacity have not been well evaluated yet. In this study, room temperature (RT) of 25°C was considered as control, and RT at 32°C for 8 h per day was set as the HS treatment. After 3 weeks, the intestinal contents of jejunum, ileum, and cecum were harvested to investigate the microbiota composition variations by 16S ribosomal RNA amplicon sequencing. And the weight gain, adipose indices, intestinal morphology, and a certain number of serum biochemical parameters were also measured and analyzed. The results showed the microbial species at different levels differentially enriched in duck jejunum and cecum under HS, while no significant data were observed in ileum. HS also caused the intestinal morphological changes (villus height and the ratio of villus height to crypt depth) and the reductions of growth speed (daily gain), levels of serum triglyceride (TG) and total cholesterol, and antioxidant activity (higher malondialdehyde (MDA) content and lower total antioxidant). The higher abdominal fat content and serum glucose level were also observed in HS ducks. The Spearman correlation analysis indicated that in jejunum the phyla Firmicutes and Proteobacteria were associated with average daily gain, feed/gain, serum TG and MDA levels, and villus height/crypt depth (P < 0.05). The phylum Firmicutes and genus Acinetobacter were significantly associated with fat deposition and serum glucose level (P < 0.05). The genus Lactobacillus was positively associated with serum total antioxidant (P < 0.05), while some other microbial species were found negatively associated, including order Pseudomonadales, genera Acinetobacter, and unidentified_Mitochondria. However, no significant correlations were observed in cecum. These findings imply the potential roles of duck gut microbiota in the intestinal injuries, fat deposition, and reductions of growth speed and antioxidant capacity caused by HS, although the molecular mechanisms requires further investigation.

Effects of Dietary Synbiotic Supplementation as an Alternative to Antibiotic on the Growth Performance, Carcass Characteristics, Meat Quality, Immunity, and Oxidative Status of Cherry Valley Ducks.

The aim of this study was to investigate the effects of synbiotic supplementation, a potential alternative to antibiotic, on growth performance, carcass characteristics, meat quality, immunity, and oxidative status of Cherry Valley ducks. In total, 540 1-day-old male Cherry Valley ducks were randomly subjected to 3 treatments, and each treatment consisted of 6 replicates with 30 birds each. Birds in the 3 treatments were fed a basal diet devoid of antibiotics (control group) or a basal diet supplemented with either 40 mg/kg zinc bacitracin or 1.5 g/kg synbiotic composed of xylooligosaccharide, Clostridium butyricum, and Bacillus subtilis for 42 days. Compared with the control group, dietary synbiotic and antibiotic supplementation decreased the feed/gain ratio of ducks (P=0.025) to a similar extent (P>0.05). Birds in the antibiotic group exhibited a lower average daily feed intake (P=0.024) whereas such an effect was not observed in the birds of the synbiotic group (P>0.05). Synbiotic and antibiotic supplementation reduced abdominal fat yield (P=0.032) and drip loss of the breast muscle (P<0.001) to similar extents (P>0.05). Additionally, synbiotic and antibiotic supplementation increased the relative weight of the bursa (P=0.005) and total superoxide dismutase activity in the ileal mucosa (P=0.025) to similar extents (P>0.05). Moreover, ileal malondialdehyde accumulation was reduced with the supplementation of synbiotic (P=0.028), but not antibiotic. The results indicated that dietary synbiotic supplementation was beneficial for growth performance, carcass compositions, meat quality, immune function, and antioxidant capacity of Cherry Valley ducks, and it could be used as an alternative to antibiotics in Cherry Valley ducks.

Characterization and Roles of Cherry Valley Duck NLRP3 in Innate Immunity During Avian Pathogenic Escherichia coli Infection.

The nucleotide-binding oligomerization domain-like receptor (NLR) pyrin domain containing 3 (NLRP3) is a pattern recognition receptor that is involved in host innate immunity and located in the cytoplasm. In the present study, the full-length cDNA of Cherry Valley duck NLRP3 (duNLRP3) (2,805 bp encode 935 amino acids) was firstly cloned from the spleen of healthy Cherry Valley ducks, and the phylogenetic tree indicated that the duNLRP3 has the closest relationship with Anas platyrhynchos in the bird branch. According to quantitative real-time PCR analysis, the duNLRP3 mRNA has a broad expression spectrum in healthy Cherry Valley duck tissues, and the highest expression is in the pancreas. There was significant up-regulation of duNLRP3 mRNA expression in the liver and down-regulation in the spleen after infection with avian pathogenic Escherichia coli (APEC) O1K1, especially at 3 days after the infection. Ducks hatched from NLRP3-lentiviral vector-injected eggs had significantly higher duNLRP3 mRNA expression in the liver, spleen, brain, and cecum, which are tissues usually with lower background expression. The mRNA expression levels of inflammatory cytokines IL-1ß, IL-18, and TNF-α significantly increased after the APEC infection in those tissues. The bacterial content in the liver and spleen decreased significantly compared with the NC-lentiviral vector-injected ducks. In addition, in the duck embryo fibroblasts, both of the overexpression and knockdown of duNLRP3 can trigger the innate immune response during the E. coli infection. Specifically, overexpression induced antibacterial activation, and knockdown reduced the antibacterial activity of the host cells. The IL-1ß, IL-18, and TNF-α mRNA expressions showed up-regulation or down-regulation. The results demonstrate that duNLRP3 has a certain antibacterial activity during E. coli infection. These findings also contribute to better understanding the importance of duNLRP3 in regulating the inflammatory response and the innate immune system of ducks.