Enteric methane from the ruminant livestock is a significant source in global greenhouse gas emissions, which is mainly generated by the methanogens inhabiting the rumen and cecum. Sika deer (Cervus nippon) not only produces less methane than bovine, but they also harbor a distinct methanogen community. Whereas, knowledge of methanogens colonization in the rumen and cecum of sika deer is relatively still unknown, which could provide more insights to the manipulation of gut microbiota during early life. Here, we examined the development of bacteria and methanogens in the rumen and cecum of juvenile sika deer from birth to post-weaning (1 day, 42 days and 70 days, respectively) based on next generation sequencing. The results showed that the facultative anaerobic bacteria were decreased and the cellulolytic bacteria were increased. However, methanogens established soon after birth thrived through the whole developmental period, indicating a different succession process than bacteria in the GIT, and the limited role of age and dietary change on GIT methanogens. We also found Methanobrevibacter spp. (Mean relative abundance = 44.2%) and Methanocorpusculum spp. (Mean relative abundance = 57.5%) were dominated in the rumen and cecum, respectively. The methanogens also formed specific correlations with bacteria under different niches, suggesting a role of ecology niche on methanogen community. This study contributes to our knowledge about the microbial succession in GIT of sika deer, that may facilitate the development of targeted strategies to improve GIT function of sika deer.

Inflammatory bowel disease (IBD) is a chronic immune-inflammatory disease. Gut microbes, intestinal immunity, and gut barrier function play a critical role in IBD. Growing evidence suggests that synbiotics may offer therapeutic benefits for individuals with colitis, suggesting an alternative therapy against colitis. With this in mind, we creatively prepared a new synbiotic combination consisting of a probiotic strain (Lactobacillus reuteri) along with one prebiotic Chitooligosaccharides (COS). The protective effect of the synbiotics on DSS-induced colitis and the underlying mechanisms were investigated. We demonstrated that the synbiotics ameliorated colitis in mice, which was evidenced by a significant reduction in body weight, shortening of the colon, and an increase in the DAI index. Notably, synbiotics reduced the intestinal inflammation and injury by synergistically decreasing inflammatory factors, inhibiting TLR4/Myd88/NF-κB/NLRP3 signaling, preventing macrophages infiltration, and enhancing the integrity of the intestinal barrier. Moreover, synbiotics selectively promoted the growth of beneficial bacteria (e.g., Akkermansia, Lactobacilus) but decreased the pathogenic bacteria (e.g. Helicobacter). BugBase's analysis supported its ameliorated role in reducing pathogenic bacteria. Collectively, our findings revealed the novel synbiotic had a potential to treat colitis, which was associated with its anti-inflammatory and microbiota-balancing properties. This study will contribute to the development of functional synbiotic products for the treatment of IBD and will provide valuable insights into their mechanisms.