Sex-Specific Differences in Gut Microbial Composition and Metabolism of Jiangshan Black Pigs

The gut microbiota plays a vital role in regulating the host's physiological functions, including metabolism and immunity. The microbial composition and metabolism are modulated by multiple factors; host sex is an important yet under-explored determinant. To investigate the sex-dependent differences in the gut microbiota within the small and large intestine, sixteen somatic mature Jiangshan black pigs (eight males and eight females) were analyzed. The ileal and colonic microbial community and metabolites were profiled using 16S rRNA gene high-throughput sequencing and gas chromatography. Distinct sex-related discrepancies were observed in both the microbial composition and metabolism of the ileum and colon. In the ileum, compared with the male group, the female group exhibited higher abundances of Unclassified <i>Chloroplast</i> and <i>Pseudomonas</i> but a lower abundance of <i>Romboutsia</i> (adjusted <i>p</i> < 0.05). Functional prediction indicated enrichment in amino acid metabolism pathway in females, with more copy numbers of genes encoding key enzymes for propionate (<i>mmdA</i>) generation and elevated valerate levels (<i>p</i> < 0.05). In the colon, compared with the male group, the female group showed higher abundances of <i>Streptococcus</i>, <i>Phascolarctobacterium,</i> and <i>Prevotella</i> spp. and lower abundances of <i>Eubacterium coprostano-ligenes group</i>, <i>Blautia</i>, <i>Christensenellaceae R-7 group</i>, and <i>Ruminococcus</i> (adjusted <i>p</i> < 0.05). Additionally, the female group had more copies of genes <i>mmdA</i> and <i>LcdA</i> (associated with lactate production), along with higher concentrations of propionate and lactate (<i>p</i> < 0.05). Correlation analysis between microbial metabolites and sex-biased bacteria further revealed that the SCFA concentration positively correlated with <i>Prevotella</i> spp. and negatively correlated with <i>Romboutsia</i>, <i>Christensenellaceae R-7 group</i>, and <i>Blautia</i>. Collectively, these findings highlight the pronounced sex-dependent discrepancies in the microbial composition and metabolism within the small and large intestines of Jiangshan black pigs, providing new insights for precisely modulating the microbiota community and metabolism in pigs according to sex.