Intestinal diseases are one of the diseases that affect the growth and immunity of deer. Currently, more lactic acid bacteria (LAB) are available as feed additives to improve the intestinal ecological balance of ruminants in production practices. In this study, Enterococcus faecalis was supplemented in the feed of fallow deer for 170 d, and body weights, blood indices and immune levels of fallow deer were counted at 35, 65 and 170 d. The effects of Enterococcus faecalis on the intestinal microbiota and the metabolism of fallow deer were analysed using 16S rDNA and UPLC-MS/MS methods. The results showed that the addition of Enterococcus faecalis to the diet improved body weight and immune function and increased the aggregation of gut microbiota in fallow deer. The addition of Enterococcus faecalis altered the community structure of intestinal microorganisms in fallow deer and increased the number of beneficial bacteria. In addition, combined with metabolomics analysis, it was found that supplementation with Enterococcus faecalis significantly altered the metabolites of fallow deer, mainly regulating lipid metabolism, carbohydrate metabolism and phospholipid metabolism. In conclusion, this study presents, for the first time, evidence that the LAB strain Enterococcus faecalis can be used as a potential probiotic for deer and points to a new direction for the treatment of intestinal disorders in the deer family.

The Chinese Milu deer (Elaphurus davidianus), an endangered species endemic to China, faces ongoing challenges, including low genetic diversity, disease threats, and declining habitat quality. Acanthamoeba spp. are common free-living amoebae widely distributed in natural environments and Entamoeba relies on a host for survival and is typically transmitted through the fecal oral route, capable of infecting numerous hosts, including humans and animals. This study presents the first investigation of Acanthamoeba spp. and Entamoeba spp. infections in the endangered Chinese Milu deer in China, aiming to assess these parasites' prevalence and epidemiological characteristics. We conducted a molecular examination on the fecal samples of Chinese Milu deer populations from five national nature reserves across different regions in China, intending to determine the presence of Acanthamoeba spp. and Entamoeba spp. infections by amplifying the SSU rRNA gene. Notably, in addition to detecting Entamoeba bovis and Entamoeba sp., the T4 and T5 genotypes of Acanthamoeba were also detected, which are associated with pathogenicity in humans and other animals. These findings highlight the potential health risks for this endangered deer and provide critical insights for future conservation and management efforts. Additionally, this study provides valuable data on the distribution and epidemiology of amoebic parasites in wildlife.

Background: Clostridium perfringens (C. perfringens) type A is a major cause of enteritis in farmed and wild deer populations, leading to significant economic losses in the deer industry. This bacterium produces toxins that damage the intestine. Methods: In this study, we performed transcriptome analysis by establishing an intestinal circulation model of the intestines of fallow deer (Dama Dama) inoculated with C. perfringens type A versus those not inoculated with C. perfringens type A. In a further step, we determined the protein content of immunoinflammation-related molecules by ELISA and the antioxidant capacity of the intestine to investigate the molecular mechanisms of C. perfringens type A-induced enteritis. Results: Transcriptome analysis revealed significant enrichment of pathways related to the haematopoietic system, oxidative stress, the immune system and intestinal tight junctions. Additionally, C. perfringens α-toxin enters the intestine and may be recognized by TLR6, activating the immune system, increasing the secretion of various cytokines and inflammasome components, inducing oxidative stress and damaging the intestine. Conclusions: This study provides a comprehensive transcriptomic basis for understanding the selective differential expression of genes in deer enteritis induced by C. perfringens type A and provides a broader guide for finding therapeutic approaches to deer enteritis.

The Milu deer ( Elaphurus davidianus ), also known as Père David's deer, has experienced severe population bottlenecks. While infectious diseases are closely monitored, baseline data on sporadic non-communicable diseases, such as neoplasia, remain scarce for wildlife disease surveillance. To date, the molecular mechanisms driving spontaneous tumorigenesis in this species remain uncharacterized. This study provides the first integrated characterization of a single facial tumor in the Milu deer, combining histopathological analysis, whole-genome sequencing (WGS), and RNA sequencing (RNA-seq). Histopathological analysis confirmed that the tumor is an epithelial neoplasm exhibiting significant mesenchymal features, indicative of epithelial-mesenchymal transition (EMT). RNA-seq differential expression analysis identified 6,537 differentially expressed genes (DEGs), while WGS revealed 114 high-confidence, tumor-specific non-synonymous somatic mutations. Functional enrichment analysis demonstrated that oncogenesis in this specific specimen is potentially driven by dysregulated cell cycle, cytoskeletal reorganization, and metabolic reprogramming mediated by PI3K-Akt and mTOR signaling. Notably, the human papillomavirus (HPV) infection pathway emerged as significantly enriched among the DEGs. We emphasize that this enrichment does not provide evidence of viral involvement, as no direct viral detection was performed; rather, it exclusively reflects the severe dysregulation of highly conserved host cellular networks implicatedin cell cycle, apoptosis, and immune regulation. By integrating mutational and transcriptomic data, we prioritized ten putative tumor-associated genes, including LGALS3, DMBT1, CHAF1A, GON4L , and SIRPA , which are linked to metastasis, immunosuppression, and proliferation. This case study provides the first integrated molecular profile of a facial tumor in the Milu deer, offering critical insights for health management of this endangered species and establishing a novel framework for comparative oncology that will inform future clinical diagnoses of neoplasms in this population.

Species rewilding, as a key strategy for rescuing endangered species and rebuilding wild populations, fundamentally relies on the behavioral plasticity of specific wildlife species. Although most current rewilding initiatives select optimal habitats, research on behavioral adaptation mechanisms in more challenging, extreme environments remains lacking. The Milu (Elaphurus davidianus), a typical wetland and plain species, naturally inhabits the warm marshlands of the Yangtze and Yellow River basins. In this study, using GPS tracking data, we focused on a population of rewilding Milu on the Inner Mongolia Plateau to investigate behavioral plasticity in terms of home range area, activity rhythm, and movement distance, aimed to elucidate their survival adaptation strategies within mid-elevation and cold environments. The results indicated significant seasonal and sex-based differences in both home range and movement distance: home ranges contract and movement distances are minimized during winter, while spatial activity expands markedly in summer—and continues to increase year by year following rewilding. During the study period, the number of daily activity peaks per individual ranged from zero to four. Furthermore, peak timing exhibited clear seasonal variation, with crepuscular patterns—morning and evening activity peaks—predominant across most months. Approximately three months after release, the activity rhythms of both males and females stabilized. These findings reveal key behavioral adjustments of Milu translocated to a mountainous, cold-temperate environment outside its original distribution range, and provide a scientific basis for long-term management and for assessing the ecological adaptability of this introduced population.

Somatic cell preservation is an effective strategy for conserving the genetic potential of endangered species. To contribute to the conservation of the Milu deer (Elaphurus davidianus), this study aimed to establish and characterize an immortalized skin fibroblast cell line (ML-iSFC). The cell line is based on fibroblasts from the skin tissue of a male fawn of Milu deer. Optimal culture conditions were determined by supplementing the culture medium with different growth factors, and immortalization was achieved through simian virus 40 large T antigen (SV40T) transduction. Optimal culturing conditions for the cells were determined by adding a range of growth factors. The cellular morphology, growth characteristics, and marker expression of the cells were further evaluated. Cell cycle and proliferation were assessed by flow cytometry and CCK-8 assays, respectively. Chromosomes were determined by karyotype analysis. The highest cell growth rate was observed when the culture medium was supplemented with 3 ng/mL of FGF2. The fibroblast-specific marker vimentin (VIM) was expressed in both ML-SFC and ML-iSFC, while the epithelial marker keratin 18 (KRT18) was weakly expressed in ML-SFC cells. Cell proliferation and cell-cycle analysis revealed that ML-iSFC exhibited a higher growth rate and greater vitality compared to ML-SFC. Karyotype analysis showed that ML-iSFC maintained the same chromosome number and morphology as ML-SFC. In summary, this study reports the successful construction of an immortalized fibroblast cell line from Milu deer, which will serve as a valuable tool for Milu deer conservation.