Abstract Specific nutrition and management interventions at farm level that aim at reducing enteric methane (CH4) production from sheep may not reduce excretion of dry matter and N, the main source of excreta CH4 production and nitrous oxide. The objectives were a) to determine the relationship of dietary variables and animal characteristics to both enteric CH4 emissions and N excretion from sheep fed ryegrass or forage brassica diets, and b) to jointly predict enteric CH4 emissions, and dry matter and N excretion from sheep based on feed intake, dietary nutrient contents and animal characteristics. A database containing 270 indirect respiration calorimetry and total excreta collection records of eight sheep studies from New Zealand was used. To explain variation in CH4 production and N excretion, all records were assigned to four categories based on CH4 emissions and N excretion being lesser or greater than the means of the entire database, viz. high CH4-high N, high CH4-low N, low CH4-high N and low CH4-low N. A redundancy analysis indicated the two low N categories were positively related to dry matter digestibility. Subsequently, dry matter digestibility was positively related to brassica forages and negatively related to ryegrass forages. Univariate modelling indicated that CH4 (g d−1) was best predicted by dry matter intake (DMI), faecal dry matter excretion (g d−1) by DMI and dietary neutral detergent fibre content, and N excretion (g d−1) by DMI and dietary crude protein content, with dry matter digestibility also contributing to the best prediction of faecal and total N. A bivariate multiple regression model for jointly predicting CH4 emission and total N excretion, and a trivariate model for also predicting faecal dry matter were developed. Key covariates included DMI, dietary neutral detergent fibre and crude protein contents, whereas DMI was replaced by body weight in the bivariate yield model (g [kg DMI]-1), and not selected for the trivariate yield model. Regression coefficients of dietary crude protein content obtained through multivariate modelling had opposite signs for CH4 emission and N excretion, indicating a trade-off. However, this trade-off was not supported by univariate modelling. Therefore, evidence for a trade-off between enteric CH4 and N excretion from sheep is limited.

中文翻译：

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绵羊肠道甲烷排放量与粪便干物质和氮排泄量的定量联合评价

摘要 农场层面旨在减少绵羊肠道甲烷 (CH4) 产量的特定营养和管理干预措施可能不会减少干物质和 N 的排泄，而 N 是排泄 CH4 和一氧化二氮的主要来源。目标是 a) 确定饮食变量和动物特征与饲喂黑麦草或牧草芸苔的绵羊肠道 CH4 排放和 N 排泄的关系，以及 b) 共同预测肠道 CH4 排放以及绵羊的干物质和 N 排泄基于饲料摄入量、日粮营养成分和动物特性。使用了一个包含 270 个间接呼吸量热法和来自新西兰的八项绵羊研究的总排泄物收集记录的数据库。为了解释 CH4 产生和 N 排泄的变化，根据 CH4 排放量和 N 排放量小于或大于整个数据库的平均值，所有记录被分配到四个类别，即。高 CH4-高 N、高 CH4-低 N、低 CH4-高 N 和低 CH4-低 N。冗余分析表明两个低 N 类别与干物质消化率呈正相关。随后，干物质消化率与芸苔草料呈正相关，与黑麦草料呈负相关。单变量模型表明 CH4 (gd-1) 最好通过干物质摄入量 (DMI)、粪便干物质排泄量 (gd-1) 和膳食中性洗涤纤维含量以及 N 排泄量 (gd-1) 和 DMI 和日粮粗蛋白含量，干物质消化率也有助于对粪便和总氮的最佳预测。开发了用于联合预测 CH4 排放和总氮排放的双变量多元回归模型，以及用于预测粪便干物质的三变量模型。关键协变量包括 DMI、膳食中性洗涤纤维和粗蛋白含量，而 DMI 在双变量产量模型中被体重替代 (g [kg DMI]-1)，而未选择用于三变量产量模型。通过多变量建模获得的日粮粗蛋白含量的回归系数对于 CH4 排放和 N 排泄具有相反的符号，表明存在权衡。但是，单变量建模不支持这种权衡。因此，关于肠道 CH4 和绵羊 N 排泄之间权衡的证据是有限的。关键协变量包括 DMI、膳食中性洗涤纤维和粗蛋白含量，而 DMI 在双变量产量模型中被体重替代 (g [kg DMI]-1)，而未选择用于三变量产量模型。通过多变量建模获得的日粮粗蛋白含量的回归系数对于 CH4 排放和 N 排泄具有相反的符号，表明存在权衡。但是，单变量建模不支持这种权衡。因此，关于肠道 CH4 和绵羊 N 排泄之间权衡的证据是有限的。关键协变量包括 DMI、膳食中性洗涤纤维和粗蛋白含量，而 DMI 在双变量产量模型中被体重替代 (g [kg DMI]-1)，而未选择用于三变量产量模型。通过多变量建模获得的日粮粗蛋白含量的回归系数对于 CH4 排放和 N 排泄具有相反的符号，表明存在权衡。但是，单变量建模不支持这种权衡。因此，关于肠道 CH4 和绵羊 N 排泄之间权衡的证据是有限的。通过多变量建模获得的日粮粗蛋白含量的回归系数对于 CH4 排放和 N 排泄具有相反的符号，表明存在权衡。但是，单变量建模不支持这种权衡。因此，关于肠道 CH4 和绵羊 N 排泄之间权衡的证据是有限的。通过多变量建模获得的日粮粗蛋白含量的回归系数对于 CH4 排放和 N 排泄具有相反的符号，表明存在权衡。但是，单变量建模不支持这种权衡。因此，关于肠道 CH4 和绵羊 N 排泄之间权衡的证据是有限的。