Coordinated endocrine, metabolomic, feeding, behavioral, and gut microbiome changes and exploratory within-individual associations during musk secretion in forest musk deer (Moschus berezovskii)

Background: Male forest musk deer secrete musk during the breeding season, a period accompanied by marked physiological and behavioral changes. To examine whether musk secretion is associated with coordinated host and gut microbiome remodeling, we conducted a paired within-individual study in captive adult males sampled before secretion and during secretion over a 3-week interval. We integrated serum hormone profiles, untargeted serum metabolomics, fecal 16S rRNA gene sequencing, and routine husbandry-based behavioral records. Results: Compared with the pre-secretion stage, the secretion stage was characterized by higher progesterone and cortisol, lower thyroxine, and metabolomic shifts consistent with enhanced steroid conjugation and altered glucocorticoid metabolism. Behavioral records indicated marked reductions in feed intake and activity, together with increased resting time during secretion. In parallel, the gut microbiome showed reduced alpha diversity and significant beta-diversity separation between stages. Taxa enriched during secretion included Escherichia-Shigella and Salmonella . Together, these multi-layer data indicate that musk secretion is associated with endocrine remodeling, reduced intake and activity, and concurrent shifts in gut microbial structure. Conclusions: Our findings support a link between seasonal endocrine remodeling and gut microbiome alteration in captive forest musk deer during musk secretion. These results highlight the importance of management practices that mitigate feed reduction and physiological stress during the secretion period, and suggest that simple monitoring of intake, rest, and gut microbiome-related indicators may help support microbial homeostasis in this endangered species.