瘤胃液对全株甜高粱青贮质量的影响

甜高粱是一种重要的能源作物,为实现长时间贮存并提升糖化效率,该研究分析了瘤胃液不同添加量对全株甜高粱青贮品质和酶解糖化效果的影响。设置R1、R3、R5和R7共4个瘤胃液处理组(添加量依序分别为1、3、5和7 mL/100 g原料)和1个对照组(CK,等量蒸馏水),考察了瘤胃液不同添加量对全株甜高粱青贮过程中有机组分、发酵品质和酶解性能等质量指标的动态影响,并跟踪解析青贮期间微生物菌群的动态演绎。结果表明,添加瘤胃液能明显减少青贮甜高粱中的干物质、水溶性碳水化合物、粗蛋白以及木质纤维组分含量,使青贮pH和氨氮含量显著下降(P0.05),并与瘤胃液添加量呈负相关。青贮中的乳酸、乙酸含量随瘤胃液添加量和青贮发酵时间延长而明显增加(P0.05),瘤胃液强化了青贮发酵并有助于减少干物质损失,尤其在较高添加量时,青贮60d时的甜高粱综纤维素含量反而有所增加。4种瘤胃液处理组的门水平优势细菌主要为厚壁菌和变形菌,厚壁菌相对丰度随时间延长和瘤胃液添加量的增加而逐渐增加,变形菌门丰度则逐渐下降;属水平主要以乳酸杆菌、泛菌和醋酸杆菌为主,乳酸杆菌丰度与时间、瘤胃液添加量呈正相关,而泛菌则呈减少趋势。瘤胃液强化青贮后的甜高粱还原糖得率显著提升,尤其瘤胃液添加量为7 mL/100 g的R7处理组的糖得率较原料分别提高了11.06%(30 d)和19.28%(60 d)。添加瘤胃液能有效改善青贮甜高粱的发酵质量和生物降解性能,起到生物强化的预处理作用,为甜高粱的乙醇化利用奠定了基础。

Effects of rumen fluid addition on the ensiling quality of whole-plant sweet sorghum

Sweet sorghum is a variety of promising energy crops with high sugar content, rapid growth rate, and strong resistance to saline-alkaline soils. Appropriate storage is highly required to utilize this feedstock for continuous bioenergy production, particularly harvested in a seasonal manner in China. In this study, the addition of rumen fluid was introduced to sweet sorghum for better ensiling quality during long-term (30 to 60 days) storage. A systematic investigation was made on the ensiling profile, including the organic components, fermentation quality, and enzymatic hydrolysis of sweet sorghum silage. Furthermore, an experimental analysis was performed on the dynamic process of microbial community during ensiling. The sweet sorghum was ensiled at 5 different dosages of rumen fluid: CK, silage without the addition of additive; R1, silage with rumen fluid at 1 mL/100 g fresh substrate; R3 at 3 mL/100 g; R5, 5 mL/100 g; R7 at 7 mL/100 g. The results showed that the contents of dry matter (DM), water-soluble carbohydrates (WSC), crude protein (CP), and ammonia nitrogen (AN) decreased significantly, as both ensiling time and dosage increased in four treatments with the addition of rumen fluid, compared with the CK silages without rumen fluid. The increased rumen fluid and prolonged ensiling contributed to reducing the content of acid detergent fiber (ADF), neutral detergent fiber (NDF), cellulose, and hemicellulose, while elevating the abundance of beneficial Lactobacillus in silages. Lignin in silages at ensiled for 60 days was effectively removed when the maximum dosage of rumen fluid was up to 7 g/100 g. There was a significant decrease in the contents of lactic acid and acetic acid, as well as the pH values in five treatments (CK, R1, R3, R5, R7), with the extension of the ensiling period (P<0.05). The contents of lactic acid and acetic acid in R7 and R5 were higher than those of treatments after 60 days, which were 9.42 g/kg (R7) and 29.08 g/kg (R5), respectively. The dominant phylum in CK silages was still Proteobacteria after ensiling, where the relative abundance was up to 96.1% and 81.2% after 30 and 60 days, respectively. However, the bacterial communities changed significantly, due to the fact the bioaugmentation of rumen fluid resulted in the coexistence of Proteobacteria and Firmicutes in bioaugmented silages. After bioaugmented ensiling for 30 days, Lactobacillus and Acetobacter became enriched in the range of 18.2-46.2% and 3.61-18.0%, respectively, as the dosage of rumen fluid increased. After 60 days of ensiling, the relative abundance of Lactobacillus increased from 45.2 (R1) to 81.1% (R7) with the increase of rumen fluid dosage. The addition of rumen fluid also enhanced the reducing sugar yield during enzymatic saccharification for 72 h. Specifically, the yields of reducing sugars in all treatments at 30 days significantly increased by 26% (CK), 30% (R1), 34% (R3), 40% (R5), and 44% (R7), respectively, compared with the raw sweet sorghum. The bioaugmented ensiling improved substantially the yield of reducing sugars, compared with the CK silages, indicating a positive correlation to the dosage of rumen fluid. It was also found that the 72 h reducing sugars yields of all silages at 60 days were significantly higher than those at 30 days. The R7 silage achieved the highest reducing sugars yield of 795.4 mg/g after 60 days of silage, indicating a linear correlation to the high biodegradation potential. The addition of rumen fluid can effectively improve the ensiling quality and biodegradability of ensiled sweet sorghum, thereby serving as biological pretreatment via bioaugmentation. This finding can provide the promising ethanol utilization of sweet sorghum.