Abstract
BACKGROUND: The forest musk deer (FMD, Moschus berezovskii), an endangered small ruminant, is listed as a class I protected wild animals in China. However, compared to their wild counterparts, captive FMD are more prone to gastrointestinal diseases caused by gut microbial dysbiosis, which severely limits population growth and increases the risk of mortality. Active dry yeast (ADY), as a commonly used feed additive, has been widely applied in domestic livestock to improve gut microbiota and enhance immune function. Whether dietary supplementation with ADY in captive FMD contributes to gut microbial homeostasis and physical health is still unclear. Thus, the study aimed to evaluate the effects of dietary supplementation with ADY on the immunity, gut microbial composition, and serum metabolites in FMD. METHODS: Fourteen male FMD from the Chongqing Institute of Medicinal Plant Cultivation (Chongqing, China), with similar initial bodyweights (7.0±0.3kg) and an average age of 4.5 years, were selected and randomly divided into two groups. The control group was fed a standard diet, while the ADY group received the standard diet supplemented with ADY at a dosage of 10 g/kg DM. RESULTS: ADY supplementation significantly increased the concentrations of immunoglobulin A (IgA), immunoglobulin G (IgG) and immunoglobulin M (IgM) in the serum. ADY improved the richness and diversity of the gut microbiota, increased the relative abundance of the Firmicutes and Bacteroidota, but decreased the relative abundance of the Proteobacteria. A widely targeted metabolomics analysis identified a total of 25 differential metabolites, with 10 being upregulated and 15 downregulated. Many differential metabolites, for example phosphatidylcholine, Glu-His, L-cysteine and other differential metabolites contributed to strengthening the immunity of the FMD by affecting arachidonic acid metabolism, linoleic acid metabolism, alpha-linolenic acid metabolism, and so on. CONCLUSION: Dietary supplementation with ADY positively impacts the immunity of FMD by modulating the composition of the gut microbial communities and serum metabolites.