Significant association of mutations close to LCORL gene with growth performance in Zhedong white geese (Anser cygnoides).

This study aimed to investigate the role of the LCORL gene in regulating the growth performance of Zhedong white (ZDW) geese, belonging to the swan geese (Anser cygnoides), and identify possible selective signatures in diverse goose breeds. Single nucleotide polymorphisms around LCORL were genotyped, and their associations with body-size-related (BSR) traits were estimated. The results showed that the genotyped loci upstream of LCORL were significantly related to the body weight and breast width of ZDW geese aged 10 weeks (p < 0.05). A genome scan comparing expected heterozygosity among different breeds identified a ~150 kb long genomic region with extremely low heterozygosity downstream of LCORL among swan geese. Further, significant associations of variants within the low heterozygosity region among ZDW geese with BSR traits, including body weight, body length and breast width (p < 0.05) were also detected. Overall, mutations adjacent to LCORL were related to the growth performance of swan geese, and the significant effects of variants in a low-heterozygosity region on BSR traits provided valuable insights into the molecular mechanism of artificial selection reshaping body stature in swan geese.

De novo assembly of a wild swan goose (Anser cygnoides) genome.

The swan goose (Anser cygnoides) is the ancestor of the Chinese domestic goose. A previous study reported a scaffold-level genome version for a Chinese indigenous goose breed, and this assembly was used as the swan goose's reference genome. To date, there is still a lack of a chromosome-level genome for the swan goose. Here, we reported a de novo assembly of the genome of a wild swan goose using an integrated strategy that combines Illumina Hiseq, Oxford Nanopore and chromosome conformation capture (Hi-C) sequencing. A total of 134.6 Gb Nanopore data with sequencing coverage of 110.33 and 69.45 Gb Illumina data with coverage of 56.93 were obtained. The genome assembly size was 1153.41 Mb, with a contig N50 of 22.75 Mb. The total size and N50 length of our assembly were larger than the previously reported scaffold-level genome version. In addition, whole-genome sequencing data of 10 geese were mapped to the previous and the current assemblies. On average, 97.88 and 93.18% of the reads were properly mapped and paired into our and the previous assemblies. This high-quality chromosome-level swan goose genome could provide a valuable resource for the utilisation of goose studies and breeding.

Using comparative genomics to detect mutations regulating plumage variations in graylag (A. anser) and swan geese (A. cygnoides).

Although graylag geese (A. anser) showed similar plumages of white, grey, and white with grey patches compared to those in swan geese (A. cygnoides), it was believed the substantial molecular mechanism for plumage variations were different. To date, studies on genes responsible for diverse plumages among graylag geese were limited and causal mutations remain unknown. In this study, genomes from 57 individuals belonging to six breeds showing different plumages were sequenced at ∼10X depth. Firstly, the allele frequency differences (AFD) of variants on the scaffold394 (NW_013185915.1) between grey and white goose breeds (A. anser) was calculated and a genomic region between 768,290-779,889 bp was detected to carry candidate variants associated with plumages, including one SNP (g. 775,151G > T, ∼18.6 kb upstream of EDNRB2) found to be fixed in white geese. This region was overlapped with the one detected by the haplotype-based sweep analysis, in which significant signals defined a candidate region of 736,610-820,622 bp on the same scaffold. Results from the transcriptomic data showed that expression levels of EDNRB2 and many other melanogenesis-related genes were significantly decreased among white geese compared to that in grey geese, especially at late embryonic stages (>E15). Modifications at transcriptional levels might result in abnormal melanocyte developments and thus the white plumages when they grow up. In addition, a frameshift mutation (C > -) in exon4 of MLANA gene on scaffold176 (NW_013185876.1) was suggested as the causal mutation for sex-linked dilution phenotype in graylag geese although this requires more demonstration experiments. Together with observed white plumages caused by EDNRB2 mutations in coding regions among swan geese and chicken, our study provided new examples to study the parallel evolution.

Isolation and Identification of a Highly Pathogenic Avian Influenza H5N6 Virus from Migratory Waterfowl in Western Mongolia.

In April 2020, two Whooper Swans (Cygnus cygnus) and one Swan Goose (Anser cygnoides) were found dead at three different locations in western Mongolia. Virus isolation from organs taken from the carcasses and full genome sequencing revealed that all three birds were positive for highly pathogenic H5N6 avian influenza virus (HPAIV) belonging to subclade 2.3.4.4h. Confirming similar reports from central Mongolia and western China, these findings have important implications for the monitoring, control, and management of HPAIVs in wild bird and commercial poultry populations in Mongolia.

Lack of conspicuous sex-biased dispersal patterns at different spatial scales in an Asian endemic goose species breeding in unpredictable steppe wetlands.

Dispersal affects the spatial distribution and population structure of species. Dispersal is often male-biased in mammals while female-biased in birds, with the notable exception of the Anatidae. In this study, we tested genetic evidence for sex-biased dispersal (SBD) in the Swan Goose Anser cygnoides, an Asian endemic and IUCN vulnerable species, which has been increasingly restricted to breeding on Mongolian steppe wetlands. We analyzed the genotypes of 278 Swan Geese samples from 14 locations at 14 microsatellite loci. Results from assignment indices, analysis of molecular variance, and five other population descriptors all failed to support significant SBD signals for the Swan Goose at the landscape level. Although overall results showed significantly high relatedness within colonies (suggesting high levels of philopatry in both sexes), local male genetic structure at the 1,050 km distance indicated greater dispersal distance for females from the eastern sector of the breeding range. Hence, local dispersal is likely scale-dependent and female-biased within the eastern breeding range. These findings are intriguing considering the prevailing expectation for there to be female fidelity in most goose species. We suggest that while behavior-related traits may have facilitated the local genetic structure for the Swan Goose, several extrinsic factors, including the decreasing availability of the nesting sites and the severe fragmentation of breeding habitats, could have contributed to the absence of SBD at the landscape level. The long-distance molt migration that is typical of goose species such as the Swan Goose may also have hampered our ability to detect SBD. Hence, we urge further genetic sampling from other areas in summer to extend our results, complemented by field observations to confirm our DNA analysis conclusions about sex-specific dispersal patterns at different spatial scales in this species.

Isolation of Mycoplasma anserisalpingitidis from swan goose (Anser cygnoides) in China.

BACKGROUND: Mycoplasma anserisalpingitidis causes significant economic losses in the domestic goose (Anser anser) industry in Europe. As 95% of the global goose production is in China where the primary species is the swan goose (Anser cygnoides), it is crucial to know whether the agent is present in this region of the world. RESULTS: Purulent cloaca and purulent or necrotic phallus inflammation were observed in affected animals which represented 1-2% of a swan goose breeding flock (75,000 animals) near Guanghzou, China, in September 2019. From twelve sampled animals the cloaca swabs of five birds (three male, two female) were demonstrated to be M. anserisalpingitidis positive by PCR and the agent was successfully isolated from the samples of three female geese. Based on whole genome sequence analysis, the examined isolate showed high genetic similarity (84.67%) with the European isolates. The antibiotic susceptibility profiles of two swan goose isolates, determined by microbroth dilution method against 12 antibiotics and an antibiotic combination were also similar to the European domestic goose ones with tylvalosin and tiamulin being the most effective drugs. CONCLUSIONS: To the best of our knowledge this is the first description of M. anserisalpingitidis infection in swan goose, thus the study highlights the importance of mycoplasmosis in the goose industry on a global scale.

Comparative analyses of the gut microbiota among three different wild geese species in the genus Anser.

In this study, we characterized for the first time the gut microbiota of Greylag geese (Anser anser) using high-throughput 16S rRNA gene sequencing technology. The results showed that the phyla Firmicutes (78.55%), Fusobacteria (9.38%), Proteobacteria (7.55%), Bacteroidetes (1.82%), Cyanobacteria (1.44%), and Actinobacteria (0.61%) dominated the gut microbial communities in the Greylag geese. Then, the variations of gut microbial community structures and functions among the three geese species, Greylag geese, Bar-headed geese (Anser indicus), and Swan geese (Anser cygnoides), were explored. The greatest gut microbial diversity was found in Bar-headed geese group, while other two groups had the least. The dominant bacterial phyla across all samples were Firmicutes and Proteobacteria, but several characteristic bacterial phyla and genera associated with each group were also detected. At all taxonomic levels, the microbial community structure of Swan geese was different from those of Greylag geese and Bar-headed geese, whereas the latter two groups were less different. Functional KEGG categories and pathways associated with carbohydrate metabolism, energy metabolism, and amino acid metabolism were differentially expressed among different geese species. Taken together, this study could provide valuable information to the vast, and yet little explored, research field of wild birds gut microbiome.

Sequencing and analyzing complete mitochondrial genome of Anser cygnoides (Anserini: Anserinae).

The complete mitogenome sequence of Anser cygnoides was determined and compared with those previously released. The whole mitogenome was 16,740 bp, with 13 protein-coding genes, 22 transfer RNA genes, 2 ribosomal RNA genes, and 1 putative non-coding region (1178 bp). The overall nucleotide composition was 30.2%, 32.0%, 15.1%, and 22.7% for A, C, G, and T, respectively. Phylogenetic analyses strongly supported two clades in Anserini and demonstrated that A. cygnoides is not monophylogenetic. This division of A. cygnoides indicates that more research is necessary to clarify phylogenetic relationships for A. cygnoides and determine how they relate to morphological traits.

Chewing Lice of Swan Geese (Anser cygnoides): New Host-Parasite Associations.

Chewing lice (Phthiraptera) that parasitize the globally threatened swan goose Anser cygnoides have been long recognized since the early 19th century, but those records were probably biased towards sampling of captive or domestic geese due to the small population size and limited distribution of its wild hosts. To better understand the lice species parasitizing swan geese that are endemic to East Asia, we collected chewing lice from 14 wild geese caught at 3 lakes in northeastern Mongolia. The lice were morphologically identified as 16 Trinoton anserinum (Fabricius, 1805), 11 Ornithobius domesticus Arnold, 2005, and 1 Anaticola anseris (Linnaeus, 1758). These species are known from other geese and swans, but all of them were new to the swan goose. This result also indicates no overlap in lice species between older records and our findings from wild birds. Thus, ectoparasites collected from domestic or captive animals may provide biased information on the occurrence, prevalence, host selection, and host-ectoparasite interactions from those on wild hosts.

Distinctive gut microbial community structure in both the wild and farmed Swan goose (Anser cygnoides).

Swan goose (Anser cygnoides) is currently one of the most popular economic wildfowl for rare birds breeding industries in several provinces of China. However, the farmed Swan geese, reared in artificial environment and fed on both natural and artificial diets, display a reduced reproductive rate compared to wild species. Little is known about the gut microbiota of this species, which could play a role in nutrient and energy metabolism, immune homeostasis and reproduction. The present comparative study was designed to provide a first characterization of gut microbial communities related to both wild and farmed Swan geese by 16 S rRNA sequences using the Illumina HiSeq platform. The results showed that dominant microbial components in both groups consisted of Firmicutes, Proteobacteria, Bacteroidetes and Actinobacteria. The abundances of these four phyla were not statistically different between the groups. At the genus level, significantly decreased abundance of Clostridium and increased abundance of SMB53, Enterococcus and Paenibacillus were observed in farmed group compared to wild group. The marked differences of genus level group-specific microbes create a baseline for future Swan goose microbiology research and make a valuable contribution to forming relationships between gut microbiota and domestic bird reproduction.

Complete mitochondrial genome of Swan goose Anser cygnoides (Anseriformes: Anatidae).

The Swan goose Anser cygnoides is a large threatened goose species in the IUCN Red List, with a natural breeding range in East Asia, migratory and wintering mainly in central and eastern China. In this study, we used PCR-based method to determine the complete mitochondrial genome (mtDNA) of this Anatidae species. The complete mtDNA is a 16,740 bp circular molecule containing 37 typical genes. The gene order is identical with that of the standard avian gene order. All protein-coding genes start with a typical ATG codon except ND5, COI and COII. The termination codon is usually the standard TAA. The non-coding region contains some inter-genic spacers and a control region.