Two aspects regarding the ruminant's contribution to global methane (CH₄) emissions were investigated: (i) testing the accuracy of the Intergovernmental Panel on Climate Change default values for dairy cows fed different diet types and differing slurry storage temperatures; and (ii) providing carbon-isotope (C-isotope) signature data to contribute information on the characteristics of ruminant-derived CH₄ as global source. The experimental diets, fed to 18 dairy cows, were separated into forage-only (hay, C₃ plant) and forage-concentrate diets (barley, C₃ plant; maize, C₄ plant). Accumulated slurry was stored at either 14 or 27°C. The hay diet had the highest CH₄ conversion rate (Y_m 7.9%). Negligible amounts of CH₄ were emitted from slurries stored at low temperature. No diet effect was found at 27°C (~33 L/kg volatile solids). The isotope ratios of enteric CH₄ averaged -67.7‰ (C₃ plants) and -57.4‰ (C₄; maize). High temperature slurry storage resulted in different enrichment factors εCO₂-CH₄ for maize (33.2‰) and hay (35.9‰). Compared with the Intergovernmental Panel on Climate Change default values for Y_m and slurry CH₄ emission the results gained in the present experiment were higher and lower, respectively. Slurry-derived CH₄ was less depleted in ¹³C than enteric CH₄, which decreases the usefulness of this signature for global ruminant-derived CH₄.

中文翻译：

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更正：政府间气候变化专门委员会反刍动物衍生甲烷及其碳同位素特征默认值的实验验证

对反刍动物对全球甲烷（CH ₄）排放的贡献进行了两个方面的研究：（i）测试政府间气候变化专门委员会针对饲喂不同日粮类型和不同浆液储存温度的奶牛默认值的准确性；（ii）提供碳同位素（C同位素）签名数据，以提供有关反刍动物来源的CH _4特性作为全球来源的信息。将饲喂18头奶牛的实验饲料分为纯饲料（干草，C ₃植物）和浓缩饲料（大麦，C ₃植物；玉米，C ₄植物）。累积的浆液储存在14或27°C下。干草饮食中CH ₄转化率最高（Y_m 7.9％）。从低温存储的浆料中排放出可忽略不计的CH ₄。在27°C（〜33 L / kg挥发性固体）下未发现饮食影响。肠道CH ₄的同位素比平均为-67.7‰（C ₃植物）和-57.4‰（C ₄玉米）。高温储浆导致不同富集因子εCO ₂ -CH ₄玉米（33.2‰）和干草（35.9‰）。与政府间气候变化专门委员会的Y _m和泥浆CH ₄排放默认值相比，本实验获得的结果分别更高和更低。浆液来源的CH ₄在^13中的消耗较少C比肠溶性CH _4少，这降低了该签名对于反刍动物衍生的CH ₄的有用性。