Dwan C, Hennessy D, Irish H, Shalloo L, Buckley F, Delaby L, Galvin N, Lahart B
Teagasc, Animal and Grassland Research and Innovation Centre, Moorepark, Fermoy, Co. Cork, P61 P302, Ireland; School of Biological, Earth and Environmental Sciences, University College Cork, Cork, T23 N73K, Ireland.
School of Biological, Earth and Environmental Sciences, University College Cork, Cork, T23 N73K, Ireland.
J Dairy Sci. 2025 Sep;108(9):9844-9860. doi: 10.3168/jds.2024-26106. Epub 2025 Jul 18.
This study aimed to quantify and compare the enteric methane emissions from dairy cows grazing either perennial ryegrass (Lolium perenne L.; PRG) or PRG with white clover (Trifolium repens L.; clover) in a farm systems experiment. A study was established with 2 sward treatments consisting of PRG receiving 225 kg of nitrogen (N) per hectare per year (grass-only) and PRG and clover receiving 150 kg N/ha per year (grass-clover). Two dairy cow genetic groups, high and low Economic Breeding Index (EBI), were randomly assigned across the 2 sward treatments, which were managed as self-contained farmlets. Enteric methane emissions were measured throughout the study (late March to late October) using GreenFeed units (C-Lock Inc.). Both swards had similar total herbage production (11.8 t DM/ha) during the study, and the average clover content of grass-clover was 23.0% (SD = 16.51). Cows in the grass-clover treatment had greater DMI and consequentially had greater daily methane emissions (341 g/d) compared with the cows in the grass-only treatment (308 g/d). However, there was no difference in methane yield (methane per kg DMI) between the 2 treatments. There was also no treatment effect when methane emissions were expressed per kilogram of milk solids (milk fat + protein; MSo), but methane per kilogram of fat- and protein-corrected milk tended to be greater from cows grazing grass-clover. There was no effect of EBI group on daily MSo production, methane emissions, methane yield, or methane per kilogram of MSo. Cows in the high EBI group had lower milk yield and greater milk fat and protein content compared with the cows in the low EBI group. The ability to reduce artificial N fertilizer inputs in a grass-clover system benefits nitrous oxide emissions and farm-gate N use efficiency. However, the greater enteric methane emissions from cows grazing grass-clover highlight the need for balanced consideration when implementing environmental measures on farms to avoid pollution swapping.
在一项农场系统试验中，本研究旨在量化和比较放牧于多年生黑麦草（Lolium perenne L.；PRG）或多年生黑麦草与白三叶草（Trifolium repens L.；三叶草）混播草地的奶牛的肠道甲烷排放量。建立了一项研究，有2种草地处理方式，一种是每年每公顷施225千克氮（N）的多年生黑麦草（仅草），另一种是每年每公顷施150千克氮的多年生黑麦草与三叶草混播草地（草 - 三叶草）。两个奶牛遗传组，即高经济育种指数（EBI）组和低经济育种指数组，被随机分配到这2种草地处理方式中，这些处理方式被作为独立的小农场进行管理。在整个研究期间（3月下旬至10月下旬），使用GreenFeed装置（C - Lock公司）测量肠道甲烷排放量。在研究期间，两种草地的总牧草产量相似（11.8吨干物质/公顷），草 - 三叶草混播草地中三叶草的平均含量为23.0%（标准差 = 16.51）。与仅吃草的奶牛（308克/天）相比，吃草 -三叶草的奶牛干物质采食量更大，因此每日甲烷排放量也更大（341克/天）。然而，两种处理方式的甲烷产量（每千克干物质采食量的甲烷量）没有差异。当按每千克乳固体（乳脂肪 + 蛋白质；MSo）表示甲烷排放量时，也没有处理效应，但吃草 - 三叶草的奶牛每千克脂肪和蛋白质校正乳的甲烷排放量往往更高。EBI组对每日MSo产量、甲烷排放量、甲烷产量或每千克MSo的甲烷量没有影响。与低EBI组的奶牛相比，高EBI组的奶牛产奶量较低，但乳脂肪和蛋白质含量较高。在草 - 三叶草系统中减少人工氮肥投入的能力有利于一氧化二氮排放和农场大门氮利用效率。然而，吃草 - 三叶草的奶牛肠道甲烷排放量更高，这突出表明在农场实施环境措施时需要进行平衡考虑，以避免污染转移。
