利用猪粪液为菌源体外发酵产气法评价牧草纤维品质

Studies on evaluation of fiber quality of fodder grass

利用体外产气法比较杂交狼尾草、优质矮化象草、柱花草的纤维品质,为牧草在猪饲养中的应用提供依据。提取牧草中的中性洗涤纤维作底物,以新鲜猪粪作为发酵菌源,39℃恒温摇床中培养24 h,测定24 h内不同时段的产气量、发酵液pH值和VFA。研究结果表明,中性洗涤纤维的含量为柱花草>杂交狼尾草>优质矮化象草,分别是69.02,61.27和54.38 g/100 g。发酵24 h,3种牧草的累积产气量杂交狼尾草最高,优质矮化象草次之,柱花草最低,分别为137.62,112.66和79.62 mL/g DM;发酵6 h以前,3种牧草的累积产气量仅占24 h平均累积产气量的7.58%。理论最大产气量杂交狼尾草与优质矮化象草均高于柱花草,分别为172.13,166.57和78.27 mL。3种牧草每克有机物发酵产生1 mL气体的持续时间表现为,柱花草<杂交狼尾草<优质矮化象草,分别为2.89,4.26和5.02 h。3种牧草达到最大产气速率的时间以优质矮化象草最高、杂交狼尾草次之、柱花草最低,分别为20.34,18.09和13.20 h。3种牧草的产气速度表现为,杂交狼尾草>优质矮化象草>柱花草,分别为10.11,8.31和6.74mL/h。研究表明,不同底物发酵24 h产生的挥发性脂肪酸中,3种酸的浓度比例发生了变化,并主要由丁酸的比例变化所引起;不同科以及同科中的不同属牧草具有不同的发酵动力学特征,主要因牧草中NDF的组成和单体的化学结构不同所致。研究给出了3种牧草体外发酵产气模型回归方程,系统分析了评定中性洗涤纤维品质的适宜指标。

Fiber quality of 3 fodder grasses was evaluated in vitro for gas production to enhance the application of fodder in swine production. Fodder NDF and pig manure bacterial substrates were incubated at 39℃ for 24 h. Gas production, pH and VFA of the fermented solutions were measured. NDF content of Stylosanthes guianensis, was highest, followed by Penniseturn alopecuroides and P. purpureurn （69.02, 61.27 and 54. 38 g/100 g, respectively）. Cumulative gas volume of P. alopecuroides was highest, followed by P. purpureurn and S. guianensis within 24 h fermentation （137.62, 112.66 and 79.62 mL/g DM, respectively）. Only 7.58% gas volume was generated during the first 6 h fermentation. Maximum theoretical gas production of P. alopecuroides and P. purpureurn was highest, followed by S. guianensis （172. 13, 166.57 and 78. 27 mL, respectively）. Sustained time of 1 mL gas generating from per gram organic matter of S. guianensis was least, followed by P. alopecuroides and P. purpureurn （2. 89, 4. 26 and 5. 02 h, respectively）. Duration of maximum gas production of P. purpureum was longest, followed by P. alopecuroides and S. guianensis （20.34, 18.09 and 13.20 h, respectively）. Speed of gas production of P. alopecuroides was highest, followed by P. purpureurn and S. guianensis （10.11, 8.31 and 6.74 mL/h, respectively）. In substrates fermented for 24 h the proportions of acetate, propionate and butyrate changed because of the butyrate. The difference in dynamic fermentation resulted from the NDF composition and chemical constitution of monomers of the different grass families or genera. The models of in vitro gas production for the above grasses are given and a feasibility index was developed to evaluate the NDF quality.