Fecal steroids, short-chain fatty acids, and microbiota in high- versus low-yielding forest musk deer

Adult male forest musk deer (Moschus berezovskii; FMD) possess high medicinal and economic value due to their musk secretion capacity. However, under farming conditions, a subset of individuals exhibit abnormal musk secretion or complete secretory failure, resulting in economic losses. This phenomenon is associated with lipid metabolism and gut microbiota alterations. We compared fecal steroid hormones, short-chain fatty acids (SCFAs), and bacterial communities between high-yielding and low-yielding FMD under identical captive conditions. Seven male FMD (2 ~ 6 years old) secreting normal musk comprised the high-yielding group (HFMD), while seven age-matched males secreting abnormal musk formed the low-yielding group (LFMD). Results showed significantly higher concentrations of testosterone (T), estradiol (E2), cortisol, and corticosterone (CORT) in HFMD versus LFMD group (p < 0.05). Conversely, SCFA levels showed an inverse pattern: butyrate and hexanoate concentrations were significantly higher in LFMD group (p < 0.05). Following multiple testing correction, the relative abundances of Fibrobacteres (p = 0.013; FDR = 0.170), Tenericutes (p = 0.013; FDR = 0.107), and Verrucomicrobia (p = 0.037; FDR = 0.223) were observed to be significantly higher in the HFMD group compared to the LFMD group. Furthermore, distinct microbial biomarkers were identified between the two groups. Certainly, ASV_849 (taxonomically classified as Ruminococcaceae UCG-014) exhibited significant correlations with multiple steroid hormones and SCFAs (p < 0.05; FDR = 0.246). Moreover, correlation analysis demonstrated positive associations between musk secretion and E2, T, cortisol, and CORT (p < 0.05), but negative correlations with hexanoate (p < 0.05). Butyrate and hexanoate were inversely correlated with T (p < 0.05). These findings reveal that the gut microbiota may regulate musk secretion through their metabolites (SCFAs), which not only play a key mediating role in microbe-host interactions but may also indirectly influence the process of musk secretion via their interplay with steroid metabolism. This study provides valuable insights into the captive care management of adult male FMD and strategies for enhancing musk secretion.