Department of Farm Animal Health, Faculty of Veterinary Medicine, Utrecht University, PO Box 80163, 3508 TD Utrecht, the Netherlands.
Department of Animal Sciences, Animal Nutrition Group, Wageningen University and Research, PO Box 338, 6700 AH, Wageningen, the Netherlands.
J Dairy Sci. 2017 Nov;100(11):8895-8905. doi: 10.3168/jds.2017-12953. Epub 2017 Aug 23.
The current study investigated the relationship between in vitro and in vivo CH production by cows fed corn silage (CS)-based rations. In vivo CH production was measured in climate respiration chambers using 8 rumen-cannulated Holstein-Friesian cows. In vitro CH production was measured using rumen fluid from the 8 cows that were fully adapted to their respective experimental rations. The animals were grouped in 2 blocks, and randomly assigned to 1 of the 4 total mixed rations (TMR) that consisted of 75% experimental CS, 20% concentrate, and 5% wheat straw [dry matter (DM) basis]. The experimental CS were prepared from whole-plant corn that was harvested at either a very early (25% DM), early (28% DM), medium (32% DM), or late (40% DM) stage of maturity. The 4 experimental TMR and the corresponding CS served as substrate in 2 separate in vitro runs (each run representing 1 block of 4 animals) using rumen fluid from cows fed the TMR in question. No relationship was found between in vivo CH production and in vitro CH production measured at various time points between 2 and 48 h. None of the in vitro gas production (GP) and CH production parameters was influenced by an interaction between substrate and origin of rumen fluid. In vitro measured 48-h GP was not affected by the maturity of whole-plant corn, irrespective whether CS alone or as part of TMR was incubated in adapted rumen inoculum. Incubation of the experimental TMR did not affect the kinetics parameters associated with gas or CH production, but when CS alone was incubated the asymptote of GP of the soluble fraction was slightly decreased with increasing maturity of CS at harvest. In vitro CH production expressed as a percent of total gas was not affected by the maturity of whole-plant corn at harvest. Several in vitro parameters were significantly affected (GP) or tended to be affected (CH) by diet fed to donor cows. It was concluded that the current in vitro technique is not suitable to predict in vivo CH production from CS-based rations.
本研究调查了以玉米青贮（CS）为基础的日粮喂养的奶牛体外和体内 CH 产量之间的关系。使用 8 头瘤胃切开的荷斯坦弗里森奶牛在气候呼吸室中测量体内 CH 产量。使用 8 头完全适应各自实验日粮的奶牛的瘤胃液测量体外 CH 产量。动物分为 2 组，随机分配到 4 种总混合日粮（TMR）中的 1 种，TMR 由 75%实验 CS、20%浓缩物和 5%小麦秸秆[干物质（DM）基础]组成。实验 CS 是由收获期为非常早期（25%DM）、早期（28%DM）、中期（32%DM）或晚期（40%DM）的全株玉米制成的。在 2 个单独的体外运行中，使用正在饲喂 TMR 的奶牛的瘤胃液作为底物，将 4 种实验 TMR 和相应的 CS 与 2 个单独的体外运行（每个运行代表饲喂 TMR 的 4 头动物的 1 个组）一起使用。在 2 至 48 小时之间的不同时间点测量的体内 CH 产量与体外 CH 产量之间未发现相关性。底物和瘤胃液来源之间的相互作用对体外气体产生（GP）和 CH 产生参数没有影响。体外测量的 48 小时 GP 不受全株玉米成熟度的影响，无论 CS 是单独还是作为 TMR 的一部分在适应的瘤胃接种物中孵育。实验 TMR 的孵育不会影响与气体或 CH 产生相关的动力学参数，但当 CS 单独孵育时，可溶性部分的 GP 渐近值随着 CS 收获时成熟度的增加而略有降低。以总气体的百分比表示的体外 CH 产量不受收获时全株玉米成熟度的影响。几个体外参数（GP）受到供体奶牛所喂食的饮食的显著影响（CH）或倾向于受到影响。结论是，目前的体外技术不适合预测基于 CS 的日粮的体内 CH 产量。
