Agricultural traits, silage quality and bacterial community structure changes of different sorghum varieties in cold regions of Hulunbuir

Selecting high-quality forage varieties is essential for stabilizing regional forage supply and enhancing feed conversion efficiency. This study evaluated agronomic traits, nutritive value, and fermentation characteristics of five forage sorghum varieties (FS3501, QCDS, F10, 3701, and DJ) from the cold Hulunbuir region of China. All cultivars were harvested at the milk-ripe stage to measure plant height and dry matter (DM) yield. Forage was chopped, vacuum-sealed, and ensiled at 25 °C for 60 days. Post-fermentation, nutritional composition and fermentation parameters were analyzed. Additionally, 16 S rRNA gene sequencing with KEGG pathway analysis assessed bacterial community structure and metabolic function dynamics.Results showed that the 3701 (SB4) variety had superior production performance, with the highest ( p < 0.05) plant height (2.54 m vs. 1.54–1.93 m) and DM yield (1567.65 kg/hm² vs. 800.40–1067.20 kg/hm²). SB4 also exhibited optimal silage fermentation, featuring the lowest pH (3.58 vs. 3.63–3.74), highest crude protein (6.79 vs. 3.44–6.43 g/kg DM), and lactic acid content (33.00 vs. 16.80–25.52 g/kg DM). Furthermore, SB4 significantly reduced neutral detergent fiber (NDF) and acid detergent fiber (ADF) levels. Microbial analysis revealed decreased α-diversity and a shift from Proteobacteria to Firmicutes, with SB4 silage dominated by Lactobacillus . KEGG functional prediction indicated that carbohydrate metabolism was the predominant metabolic pathway. These findings highlight SB4 as a superior forage variety suitable for cultivation and silage production in high-latitude cold regions like Hulunbuir.