Eun J S, Fellner V, Gumpertz M L
Department of Animal Science, North Carolina State University, Raleigh 27695, USA.
J Dairy Sci. 2004 Jan;87(1):112-21. doi: 10.3168/jds.S0022-0302(04)73148-3.
This study evaluated the effects of dilution rate and forage-to-concentrate ratio on gas production by rumen microbes. Continuous cultures were used to monitor methane production at three liquid dilution rates (3.2, 6.3, or 12.5%/h) and three forage-to-concentrate ratios (70:30, 50:50, or 30:70). Filtered ruminal contents were allowed 6 d of adaptation to diets followed by 7 d of data collection. Forage consisted of pelleted alfalfa and the concentrate mix included ground corn, soybean meal, and a mineral and vitamin premix. The experiment was replicated in a split-plot design. Total volatile fatty acid production averaged 58.0 mmol/d and was not affected by treatment. Molar proportion of acetate increased with increasing forage-to-concentrate ratio. Molar proportion of propionate tended to decrease at dilution rate of 12.5%/h and increased with the medium and low forage-to-concentrate ratio. Culture pH tended to be greater at a dilution rate of 12.5%/h. Methane production that was calculated from stoichiometric equations was not affected by treatments. However, methane production based on methane concentration in fermentor headspace resulted in an interaction effect of treatments. Stoichiometric equations underestimated methane output at higher dilution rates and with high forage diets. Total diet fermentability was lowest at dilution rate of 3.2%/h. Increasing dilution rates increased microbial yield; increasing the proportion of concentrate improved microbial efficiency. Dilution rate and forage-to-concentrate ratio altered the partition of substrate by microbes. Methane production based on actual concentrations differed from values estimated using stoichiometry of end-product appearance.
本研究评估了稀释率和饲草与精料比例对瘤胃微生物产气的影响。采用连续培养法，在三种液体稀释率（3.2%/小时、6.3%/小时或12.5%/小时）和三种饲草与精料比例（70:30、50:50或30:70）下监测甲烷产生情况。过滤后的瘤胃液内容物先让其适应日粮6天，然后进行7天的数据收集。饲草由苜蓿颗粒组成，精料混合物包括玉米粉、豆粕以及矿物质和维生素预混料。实验采用裂区设计进行重复。总挥发性脂肪酸产量平均为58.0 mmol/天，不受处理影响。乙酸的摩尔比例随饲草与精料比例的增加而增加。丙酸的摩尔比例在稀释率为12.5%/小时时趋于下降，在中等和低饲草与精料比例时增加。培养物pH值在稀释率为12.5%/小时时往往更高。根据化学计量方程计算的甲烷产量不受处理影响。然而，基于发酵罐顶空甲烷浓度的甲烷产量产生了处理的交互作用。化学计量方程在较高稀释率和高饲草日粮条件下低估了甲烷产量。日粮总发酵性在稀释率为3.2%/小时时最低。增加稀释率可提高微生物产量；增加精料比例可提高微生物效率。稀释率和饲草与精料比例改变了微生物对底物的分配。基于实际浓度的甲烷产量与使用终产物出现的化学计量法估计的值不同。
