The relationship between DM intake (DMI) and enteric methane emission is well established in ruminant animals but may depend on measurement technique (e.g. spot v. continuous gas sampling) and rumen environment (e.g. use of fermentation modifiers). A previous meta-analysis has shown a poor overall (i.e. 24 h) relationship of DMI with enteric methane emission in lactating dairy cows when measured using the GreenFeed system (GF; Symposium review: uncertainties in enteric methane inventories, measurement techniques, and prediction models. Journal of Dairy Science 101, 6655 to 6674). Therefore, we examined this relationship in a 15-week experiment with lactating dairy cows receiving a control diet or a diet containing the investigational product 3-nitrooxypropanol (3-NOP), an enteric methane inhibitor, applied at 60 mg/kg feed DM. Daily methane emission, measured using GF, and DMI were clustered into 12 feed-intake timeslots of 2 h each. Methane emission and DMI were the lowest 2 h before feeding and the highest within 6 h after feed provision. The overall (24 h) relationship between methane emission and DMI was poor (R2 = 0.01). The relationship for the control (but not 3-NOP) cows was improved (R2 = 0.31; P < 0.001) when DMI was allocated to timeslots and was strongest (R2 = 0.51; P < 0.001) 8 to 10 h after feed provision. Analysis of the 3-NOP emission data showed marked differences in the mitigation effect over time. There was a lack of effect in the 2-h timeslot before feeding, the mitigation effect was highest (45%) immediately after feed provision, persisted at around 32% to 39% within 10 h after feed provision, and decreased to 13%, 4 h before feeding. These trends were clearly related to DMI (i.e. 3-NOP intake) by the cows. The current analysis showed that the relationship of enteric methane emission, as measured using GF, and DMI in dairy cows depends on the time of measurement relative to time of feeding. The implication of this finding is that a sufficient number of observations, covering the entire 24-h feeding cycle, have to be collected to have representative emission estimates using the GF system. This analysis also revealed that the methane mitigation effect of 3-NOP is highest immediately after feed provision and lowest before feeding.

干物质采食量（的关系DMI）和肠溶甲烷排放是公认的在反刍动物，但可依赖于测量技术（例如点v。连续的气体取样）和瘤胃环境（例如使用的发酵改性剂）。使用绿色饲料系统中测量时先前的荟萃分析已经显示出较差的整体（即，24小时），DMI的用肠溶甲烷排放在奶牛关系（GF; 专题讨论会回顾：肠甲烷库存，测量技术和预测模型的不确定性。乳科学杂志101，6655至6674）。因此，我们在一个为期15周的实验中检查了这种关系，其中泌乳奶牛接受了对照饮食或含有试验性产品3-硝基氧丙醇（3-NOP）（一种肠甲烷抑制剂）的饮食，以DM饲料60 mg / kg施用。使用GF和DMI测得的每日甲烷排放量被分为12个各自2小时的进料时隙。饲喂前2 h甲烷排放量和DMI最低，饲喂后6 h内甲烷排放量和DMI最高。甲烷排放与DMI之间的总体（24 h）关系很差（R 2= 0.01）。当将DMI分配给时隙时，对照组（而非3-NOP）奶牛的关系得到改善（R 2 = 0.31；P <0.001），并且最强（R 2 = 0.51；P<0.001）喂食后8至10小时。对3-NOP排放数据的分析表明，随着时间的推移，缓解效果存在明显差异。喂食前2小时的时间里没有效果，喂食后的缓解效果最高（45％），喂食后10小时内的缓解效果持续在32％至39％左右，而降低到13％，喂食前4小时。这些趋势显然与奶牛的DMI（即3-NOP摄入量）有关。目前的分析表明，奶牛使用GF和DMI测得的肠内甲烷排放量的关系取决于相对于喂养时间的测量时间。该发现的含义是，必须收集足够的观测值，覆盖整个24小时的饲喂周期，才能使用GF系统获得具有代表性的排放估算值。