Zhao Jie, Wang Siran, Dong Zhihao, Li Junfeng, Jia Yushan, Shao Tao
Institute of Ensiling and Processing of Grass, College of Agro-grassland Science, Nanjing Agricultural University, Nanjing 210095, China.
Key Laboratory of Forage Cultivation, Processing and High Efficient Utilization of Ministry of Agriculture, Inner Mongolia Agricultural University, Hohhot 010018, China.
Anim Biosci. 2021 Jun;34(6):1038-1048. doi: 10.5713/ajas.20.0388. Epub 2021 Apr 22.
The study aimed to evaluate the effect of storage time and formic acid (FA) on fermentation characteristics, epiphytic microflora, carbohydrate components and in vitro digestibility of rice straw silage.
Fresh rice straw was ensiled with four levels of FA (0%, 0.2%, 0.4%, and 0.6% of fresh weight) for 3, 6, 9, 15, 30, and 60 d. At each time point, the silos were opened and sampled for chemical and microbial analyses. Meanwhile, the fresh and 60-d ensiled rice straw were further subjected to in vitro analyses.
The results showed that 0.2% and 0.6% FA both produced well-preserved silages with low pH value and undetected butyric acid, whereas it was converse for 0.4% FA. The populations of enterobacteria, yeasts, moulds and aerobic bacteria were suppressed by 0.2% and 0.6% FA, resulting in lower dry matter loss, ammonia nitrogen and ethanol content (p<0.05). The increase of FA linearly (p<0.001) decreased neutral detergent fibre and hemicellulose, linearly (p<0.001) increased residual water soluble carbohydrate, glucose, fructose and xylose. The in vitro gas production of rice straw was decreased by ensilage but the initial gas production rate was increased, and further improved by FA application (p<0.05). No obvious difference of FA application on in vitro digestibility of dry matter, neutral detergent fibre, and acid detergent fibre was observed (p>0.05).
The 0.2% FA application level promoted lactic acid fermentation while 0.6% FA restricted all microbial fermentation of rice straw silages. Rice straw ensiled with 0.2% FA or 0.6% FA improved its nutrient preservation without affecting digestion, with the 0.6% FA level best.
本研究旨在评估储存时间和甲酸（FA）对稻草青贮饲料发酵特性、附生微生物菌群、碳水化合物成分及体外消化率的影响。
将新鲜稻草与四种水平的甲酸（占鲜重的0%、0.2%、0.4%和0.6%）青贮3、6、9、15、30和60天。在每个时间点，打开青贮窖并取样进行化学和微生物分析。同时，对新鲜和青贮60天的稻草进行体外分析。
结果表明，0.2%和0.6%的甲酸均能产生保存良好的青贮饲料，pH值较低且未检测到丁酸，而0.4%的甲酸情况则相反。0.2%和0.6%的甲酸抑制了肠杆菌、酵母、霉菌和好氧细菌的数量，导致干物质损失、氨氮和乙醇含量降低（p<0.05）。甲酸用量的增加使中性洗涤纤维和半纤维素呈线性下降（p<0.001），残余水溶性碳水化合物、葡萄糖、果糖和木糖呈线性增加（p<0.001）。青贮使稻草的体外产气量降低，但初始产气速率提高，且添加甲酸进一步改善了这一情况（p<0.05）。未观察到添加甲酸对干物质、中性洗涤纤维和酸性洗涤纤维体外消化率有明显差异（p>0.05）。
添加0.2%的甲酸促进了乳酸发酵，而添加0.6%的甲酸则抑制了稻草青贮饲料的所有微生物发酵。添加0.2%或0.6%甲酸青贮的稻草改善了其营养保存，且不影响消化，其中添加0.6%甲酸的效果最佳。
