Abstract: Aiming at low utilization efficiency of corn and broom sorghum straw raw materials in rural Balin Left Banner， Chifeng， and beef cattle malnutrition caused by farmers' lack of dietary knowledge， this study explored changes in nutritional quality，fermentation characteristics，in vitro digestibility and microbial community of total mixed rations（TMR）with different straw ratios during room-temperature storage，to provide basis for straw feed utilization and beef cattle feeding. Five groups with corn straw：broom sorghum straw raw ratios of 9∶1，8∶2，7∶3，6∶4，5∶5 were set，mixed with concentrate to prepare TMR with 50%moisture content，sealed in ethylene plastic bags.Samples were collected at 0，2，5，7，10，15 days（3 replicates per group）for index determination and sequencing. with prolonged storage， dry matter（DM），crude protein（CP），water-soluble carbohydrates（WSC），neutral detergent fiber（NDF），and acid detergent fiber（ADF）of all groups decreased（P<0.05），and DM loss was lower in high broom sorghum straw raw groups； pH increased with trace detected propanoic acid and butyric acid （P<0.05）；after 2 days， bacteria were dominated by Pantoea（increasing pH）and Bacillus（promoting DM loss），while fungi were dominated by Alternaria and Clavispora（causing mildew，positively correlated with nutrient loss）. TMR decays within 2 days at room temperature；low broom sorghum straw raw groups are prone to deterioration due to WSC depletion，while high-ratio groups delay decay but have insufficient acidification. Proliferation of aerobic bacteria and molds is the key for the decay. It is suggested to select high broom sorghum straw raw formula for short-term feeding， and to use airtight packaging and control storage time.

Key words: Straw, Total mixed ration, Fermentation, Nutritional quality, Fermentation quality, In vitro digestibility, Microbial community dynamics

摘要： 针对赤峰巴林左旗农村玉米与笤帚糜子秸秆利用率低、养殖户因日粮知识匮乏致肉牛营养不良的问题，本研究探究不同秸秆比例全混合日粮（Total mixed ration，TMR）常温贮藏期的营养品质、发酵特性、体外消化率及微生物群落变化，为秸秆饲料化与肉牛饲喂提供依据。设玉米秸秆∶笤帚糜子秸秆=9∶1，8∶2，7∶3，6∶4，5∶5五组，与精料混合制成50%含水量TMR，密封于乙烯塑料袋，于0，2，5，7，10，15 d取样（每组3个重复），测定相关指标并测序。随着贮藏时间延长，各组干物质（Dry matter，DM）、粗蛋白（Crude protein，CP）和可溶性碳水化合物（Water-soluble carbohydrates，WSC）、中性洗涤纤维（Neutral detergent fiber，NDF）、酸洗洗涤纤维（Acid detergent fiber，ADF）均下降（P<0.05），高比例笤帚糜子秸秆组DM损失低；pH值升高，检出微量丙酸（Propanoic acid，PA）和丁酸（Butyric acid，BA）（P<0.05）；2 d后细菌以泛菌属（Pantoea）和芽孢杆菌属（Bacillus）为主，真菌以链格孢属（Alternaria）和锁掷酵母属（Clavispora）为主。TMR常温2 d内即腐败，低笤帚糜子秸秆组因WSC耗竭易劣变，高比例组延缓腐败但酸化不足，好氧菌与霉菌增殖是关键。建议短期饲喂选高笤帚糜子秸秆配方，用气密性包装并控制贮藏时间。

关键词: 秸秆, 全混合日粮, 发酵, 营养品质, 发酵品质, 体外消化率, 微生物群落动态