Characteristics of the gastrointestinal tract and volatile fatty acids in plateau ruminants

High-altitude ruminants face environmental stressors such as low temperature, hypoxia, and short grazing seasons, which challenge energy acquisition and nutrient absorption. The gastrointestinal tract (GIT) plays a central role in metabolic adaptation. In this study, we collected contents from the rumen, reticulum, omasum, abomasum, duodenum, jejunum, cecum, and rectum of Pamir yaks. Microbial composition and metabolic functions across GIT regions were investigated through volatile fatty acid (VFA) determination and 16S rRNA gene sequencing. The results showed that the total VFA concentrations were highest in the forestomach and lowest in the small intestine, with the hindgut showing intermediate levels. Microbial diversity was highest in the reticulum and lowest in the jejunum. At the phylum level, Firmicutes, Bacteroidota, and Proteobacteria were the dominant bacterial taxa. At the genus level, <i>Prevotella, Rikenellaceae_RC9_gut_group</i>, <i>UCG-005</i>, <i>Muribaculaceae</i>, and <i>Christensenellaceae_R-7_group</i> were the predominant genera. Functional predictions revealed that the forestomach exhibited a notable enrichment in metabolic pathways associated with carbohydrate, amino acid, and nucleotide metabolism. In contrast, the abomasum and small intestine showed significant enrichment in pathways related to nucleotide and nucleotide-sugar metabolism, protein synthesis, and DNA repair. The hindgut demonstrated enrichment in butyrate metabolism and immune-related pathways. This study highlights the spatial heterogeneity of VFAs, microbial communities, and functional potentials in the GIT, providing theoretical insights into the adaptive mechanisms of energy metabolism in high-altitude ruminants.IMPORTANCEThis study systematically characterized microbial community composition and volatile fatty acid (VFA) metabolic profiles across different segments of the gastrointestinal tract in plateau ruminants. The results revealed potential metabolic adaptation strategies to extreme conditions such as hypoxia, low temperature, and limited forage availability. The forestomach was identified as the primary site of energy acquisition and showed a marked enrichment of VFA-producing bacteria. Microbial diversity in the small intestine was relatively low, but metabolic pathways associated with nutrient absorption remained highly active. The hindgut exhibited distinct microbial colonization patterns and signs of potential metabolic compensation. Collectively, these findings provided important theoretical insights into nutritional regulation, ecological adaptation, and microecological intervention strategies in plateau ruminants. They also filled a critical gap in high-altitude animal microbiome research and offer significant scientific and practical implications.