Grant R J, Mertens D R
US Dairy Forage Research Center, USDA-Agricultural Research Service, Madison, WI 53706.
J Dairy Sci. 1992 May;75(5):1263-72. doi: 10.3168/jds.S0022-0302(92)77876-X.
Three in vitro fermentation experiments were conducted to examine the impact on kinetics of fiber digestion of microminerals and tryptone addition, media reduction, fermentation vessel, CO2 gassing regimen, and buffer type. Alfalfa and bromegrass hays were incubated for 0, 4, 8, 12, 18, 24, 30, 36, 48, 72, and 96 h and analyzed for NDF. Kinetic measures of fiber digestion were estimated using nonlinear regression with iteratively reweighted least squares. In Experiment 1, continuous CO2 gassing increased rate and decreased lag time prior to NDF digestion compared with purging a non-CO2-saturated buffer at inoculation. Vessel type (50-ml polypropylene tube, 125-ml pyrex Erlenmeyer flask), use of additives (microminerals, tryptone), and media reduction had no effect on kinetics of NDF digestion. In Experiment 2, elimination of both media reduction and nutritive additives increased the lag time prior to NDF digestion. In Experiment 3, continuous CO2 gassing of buffer in 125-ml Erlenmeyer flasks resulted in faster rates of NDF digestion than CO2-saturated buffer in 50-ml screw-cap polypropylene tubes. The method that yielded the fastest rates and shortest lag times of NDF digestion consisted of continuous CO2 gassing, reduction, and use of additives to ensure that no nutrient limited fiber digestion.
进行了三项体外发酵实验，以研究微量矿物质和添加胰蛋白胨、培养基还原、发酵容器、二氧化碳通气方案以及缓冲液类型对纤维消化动力学的影响。将苜蓿和雀麦干草分别培养0、4、8、12、18、24、30、36、48、72和96小时，并分析中性洗涤纤维（NDF）。使用迭代加权最小二乘法的非线性回归估计纤维消化的动力学指标。在实验1中，与接种时吹扫未饱和二氧化碳的缓冲液相比，持续通入二氧化碳可提高NDF消化速率并缩短滞后时间。容器类型（50毫升聚丙烯管、125毫升派热克斯锥形瓶）、添加剂（微量矿物质、胰蛋白胨）的使用以及培养基还原对NDF消化动力学没有影响。在实验2中，消除培养基还原和营养添加剂会增加NDF消化前的滞后时间。在实验3中，在125毫升锥形瓶中对缓冲液持续通入二氧化碳比在50毫升螺帽聚丙烯管中使用饱和二氧化碳缓冲液导致NDF消化速率更快。产生最快NDF消化速率和最短滞后时间的方法包括持续通入二氧化碳、还原以及使用添加剂以确保没有营养物质限制纤维消化。
