Effect of Baijiu bottom pot water on the chemical composition, microbial community and in vitro ruminal fermentation of king grass silage

Bottom pot water (BPW), a distillation by-product from the Baijiu industry, is rich in organic compounds but poses a disposal challenge. This study investigated the effects of BPW and Lentilactobacillus buchneri , on fermentation quality, chemical profiles, and bacterial community dynamics during king grass ensiling, as well as the subsequent in vitro ruminal fermentation performance of the resulting silage. Fresh king grass ( Pennisetum × sinese ) was ensiled without additives (CK) or supplemented with Lentilactobacillus buchneri (L) and BPW at 1% (B2) or 2% (B4) of fresh matter (FM), followed by anaerobic storage for 60 days. Then they were subjected to in vitro ruminal fermentation and gas production analyses. The results showed that the overall fermentation quality was poor across all treatments; however, BPW inhibited spoilage products and optimized microbiota. Compared with CK, the B4 treatment reduced propionic acid, butyric acid, and ammonia-N concentrations by 71%, 39%, and 11%, respectively. 16S rRNA gene sequencing revealed that B4 increased the relative abundance of Lactobacillus by 8%-18% compared with CK. During subsequent in vitro ruminal fermentation, BPW supplementation reduced estimated methane (CH 4 ) production by 15–35%. The estimated CH 4 production per unit of degraded dry matter decreased by 13.2% in the B4 treatment without affecting its yield relative to total volatile fatty acid production. Collectively, these findings suggest that BPW may serve as a potential additive for valorizing distillery by‑products while mitigating estimated CH₄ production in ruminant feed systems.