Fermentation characteristics of elephant grass silages with macaúba cake

ABSTRACT. The elephant grass presents problems during the fermentation of the ensiled material, being necessary use of additives. This study aimed to evaluate the population of yeast and filamentous fungi, enterobacterias, contents of acetic and butyric acids and ethanol production, in elephant grass silages added with different levels of macaúba cake at opening times. This was a 3 x 6 factorial completely randomized experimental design, with three inclusion levels of the macaúba cake (0, 10 and 20%) and six opening times (1, 5, 10, 20, 40 and 60 days after ensiling), with four replications. For all the studied variables, there was a difference in the interaction among levels and times, and an increasing linear behavior only for the contents of acetic acid, for the other variables, the behavior was quadratic. The elephant grass silages produced acetic acid, which in turn inhibited the production of yeast and filamentous fungi. There was a small development of enterobacterias only in the first opening times, and low production of butyric acid and ethanol, which indicated a material with good fermentative characteristics. The macaúba cake contributed to improve the anaerobic fermentation process, but it was not as expressive for the parameters evaluated in this work.

摘要
象草在青贮物料发酵过程中存在工艺难题，需借助添加剂优化发酵效果。本研究旨在评估添加不同水平马卡乌巴饼（Macaúba cake）的象草青贮料，在不同开封时间下的酵母菌（yeast）与丝状真菌（filamentous fungi）种群数量、肠杆菌（enterobacterias）含量，以及乙酸（acetic acid）、丁酸（butyric acid）含量与乙醇（ethanol）生成量。
本试验采用3×6析因完全随机试验设计，马卡乌巴饼添加水平设为0、10%、20%共3个梯度，开封时间设为青贮后1、5、10、20、40、60天共6个时间点，每组设置4次重复。
所有受试指标均呈现添加水平与开封时间的交互效应，其中仅乙酸含量呈线性递增趋势，其余指标均呈现二次变化趋势。
象草青贮料可合成乙酸，而乙酸可抑制酵母菌与丝状真菌的增殖。仅在初始开封时间点检测到少量肠杆菌增殖，丁酸与乙醇生成量均处于较低水平，表明该青贮物料具备优良的发酵特性。
马卡乌巴饼有助于优化厌氧发酵过程，但对本研究评估的各项指标的提升效果并不显著。