Integrated microbial and metabolic coordination orchestrates antler growth induced by guar gum and xylo-oligosaccharides.

Antlers are a unique mammalian bone organ characterized by rapid growth, a process critically dependent on nutrient availability and the gastrointestinal tract microbiome. Polysaccharides and oligosaccharides shape microbiome output, but their roles in antler development remain unclear. Here, the strongest short-chain fatty acid effect was found with guar gum (GG) and xylo-oligosaccharides, which altered the rumen microbiome in vitro incubations with six polysaccharides and oligosaccharides. GG enriched Lachnospiraceae and Oscillospiraceae, and glycoside hydrolase families, enhancing butyrate biosynthesis and amino acid catabolism, while xylo-oligosaccharides selectively enriched Selenomonadaceae, supporting vitamin and fatty acid biosynthesis in vivo in the rumen. GG increased the fecal microbiome involved in bile acid deconjugation and dihydroxylation. Targeted metabolomics demonstrated that GG elevated the circulating levels of bile acids (chenodeoxycholic acid, deoxycholic acid, taurohyodeoxycholic acid) and osteogenic factors (IGF-1, BMP2, FGF2), and resulted in free fatty acid changes in the serum. Transcriptomics and RT-PCR revealed activation of angiogenic pathways in reserve mesenchyme and osteogenic signaling in mineralized cartilage of antlers. In vitro assays demonstrated that taurohyodeoxycholic acid significantly promoted osteogenic differentiation of mesenchymal cells. Our results revealed the distinct microbial adaptations of specific carbohydrates and elucidated a "GIT-antler" axis intervention for enhancing bone growth in mammals.