An experiment was conducted to evaluate the effects of different proportions of ‘Au Grazer’ sericea lespedeza [SL, Lespedeza cuneata (Dum. Cours.) G. Don], a legume rich in condensed tannins (CT), on nutrient intake and digestibility, and to estimate methane (CH4) emissions and 13C isotopic composition (δ13CCH4) from beef steers consuming a forage-based diet. Twenty-five Angus-crossbred steers were distributed in a randomized complete block design (344 ± 48 kg initial BW), and randomly assigned to one of five treatments: 0SL, 25SL, 50SL, 75SL, and 100SL, diets containing 0%, 25%, 50%, 75%, and 100% of SL hay, respectively, mixed with ‘Tifton-85’ bermudagrass hay (Cynodon spp.). The study was carried out for two experimental periods of 21-d each. The statistical model included the fixed effect of treatment and random effects of block, experimental period, and their interaction. Apparent total tract digestibility of crude protein, neutral detergent fiber, and acid detergent fiber was linearly decreased (P < 0.001) by the inclusion of SL. No effects were observed for total CH4 emissions per day, nor for CH4 relative to organic matter intake or digestible organic matter with the inclusion of SL. However, emission of CH4 in relation to intake of CT was affected by treatment (P < 0.001). A linear (P < 0.001) decrease and a quadratic effect (P < 0.001) were observed for δ13C of diets and gas, respectively, in which diets and enteric CH4 with greater inclusion of SL were more depleted in 13C. Moreover, the difference in δ13C between diets and gas (Δδ13C) had a linear decrease (P = 0.001) with the inclusion of SL. The model developed to predict the C3 proportions in the enteric CH4 fitted to predicted values (P < 0.0001). Therefore, greater proportions of SL resulted in lesser CH4 emission when CT intake was considered and the isotopic composition from enteric CH4 was able to predict the contribution of SL in the emissions.

中文翻译：

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食用百慕大草干草日粮中越来越多的海参干草的肉牛产生的甲烷排放和 δ13C 成分

进行了一项实验以评估不同比例的'Au Grazer' sericea lespedeza [SL, Lespedeza cuneata (Dum. Cours.) G. Don]，一种富含浓缩单宁 (CT) 的豆类，对营养摄入和消化率的影响，并估算食用草料日粮的肉牛的甲烷 (CH4) 排放量和 13C 同位素组成 (δ13CCH4)。25 头安格斯杂交肉牛以随机完整区组设计（初始体重 344 ± 48 kg）分布，并随机分配到五种处理中的一种：0SL、25SL、50SL、75SL 和 100SL，日粮含 0%、25 %、50%、75% 和 100% 的 SL 干草分别与“Tifton-85”狗牙根干草（Cynodon spp.）混合。该研究进行了两个实验期，每个实验期为 21 天。统计模型包括治疗的固定效应和块的随机效应，实验期，以及它们的相互作用。加入 SL 后，粗蛋白、中性洗涤纤维和酸性洗涤纤维的表观全消化道消化率呈线性下降（P < 0.001）。没有观察到对每天总 CH4 排放量的影响，也没有观察到 CH4 相对于有机物质摄入量或包含 SL 的可消化有机物质。然而，与 CT 摄入量相关的 CH4 排放量受到治疗的影响（P < 0.001）。对于日粮和气体的 δ13C，分别观察到线性 (P < 0.001) 下降和二次效应 (P < 0.001)，其中含有更多 SL 的日粮和肠道 CH4 在 13C 中消耗得更多。此外，随着 SL 的加入，日粮和气体之间的 δ13C 差异 (Δδ13C) 呈线性下降 (P = 0.001)。该模型开发用于预测符合预测值的肠道 CH4 中的 C3 比例 (P < 0.0001)。因此，当考虑 CT 摄入量时，较大比例的 SL 导致较少的 CH4 排放，并且肠道 CH4 的同位素组成能够预测 SL 在排放中的贡献。