Despite the multiple definitions currently used to express enteric methane emissions from ruminants, no consensus has been reached on the most appropriate definition. The objective of the present study was to explore alternative trait definitions reflecting animal level differences in enteric methane emissions in growing cattle. It is likely that no single methane trait definition will be best suited to all intended use cases, but at least, knowing the relationships between the different traits may help inform the selection process. The research aimed to understand the complex interrelationships between traditional and novel methane traits and their association with performance traits across multiple breeds and sexes of cattle; also of interest was the extent of variability in daily enteric methane emissions independent of performance traits like feed intake, growth and live-weight. Methane and carbon dioxide data were collected using the Greenfeed system on 939 growing crossbred cattle from a commercial feedlot. Performance traits including feed intake, feeding behavior, liveweight, live animal ultrasound, subjectively scored skeletal and muscular traits, and slaughter data were also available. A total of 13 different methane traits were generated, including (average) daily methane production, five ratio traits and seven residual methane (RMP) traits. The RMP traits were defined as methane production adjusted statistically for different combinations of the performance traits of energy intake, liveweight, average daily gain and carcass weight; terms reflecting systematic effects were also included in the fixed effects linear models. Of the performance traits investigated, liveweight and energy intake individually explained more of the variability in methane production than growth rate or fat. All definitions of RMP were strongly phenotypically correlated with each other (>0.90) as well as with methane production itself (>0.86); the RMP traits were also moderately correlated with the methane ratio traits (>0.57). The dataset included heifers, steers and bulls; bulls were either fed a total mixed ration or ad lib concentrates. When all sexes fed total mixed ration were compared, bulls, on average, emitted the most enteric methane per day of 269.53g, while heifers and steers produced 237.54g and 253.26g, respectively. Breed differences in the methane traits existed, with Limousins, on average, producing the least amount of methane of the breeds investigated. Herefords and Montbéliardes produced 124.50g and 130.77g more methane per day, respectively, than Limousins. The most efficient 10% of test-day records, as defined by daily methane independent of both energy intake and liveweight emitted, on average, 54.60 g/d less methane than animals that were average for daily methane independent of both energy intake and liveweight. This equates to 6.5kg less methane production per animal over a 120-day finishing period for the same feed intake and liveweight.

中文翻译：

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室内饲养生长牛的一系列肠道甲烷排放性状与性能性状之间的关联


尽管目前有多种定义用于表示反刍动物肠道甲烷排放，但尚未就最合适的定义达成共识。本研究的目的是探索反映生长牛肠道甲烷排放动物水平差异的替代性状定义。很可能没有一个单一的甲烷性状定义最适合所有预期用例，但至少，了解不同性状之间的关系可能有助于为选择过程提供信息。该研究旨在了解传统和新型甲烷性状之间的复杂相互关系，以及它们与多种品种和性别牛的性能性状的关联;同样有趣的是每日肠道甲烷排放的可变程度，与采食量、生长和活重等性能特征无关。使用 Greenfeed 系统收集了来自商业饲养场的 939 头生长中的杂交牛的甲烷和二氧化碳数据。性能特征包括采食量、摄食行为、活重、活体动物超声、主观评分的骨骼和肌肉特征以及屠宰数据。共生成了 13 种不同的甲烷性状，包括（平均）每日甲烷产量、5 个比率性状和 7 个残余甲烷 （RMP） 性状。RMP 性状定义为根据能量摄入、活重、平均日增重和胴体重量的性能性状的不同组合对甲烷产生进行统计调整;反映系统效应的术语也包含在固定效应线性模型中。 在研究的性能特征中，活重和能量摄入单独解释了甲烷产生的可变性，而不是生长速率或脂肪。RMP 的所有定义在表型上彼此之间 （>0.90） 以及与甲烷产生本身 （>0.86） 具有很强的表型相关性;RMP 性状也与甲烷比性状呈中度相关 （>0.57）。数据集包括小母牛、公牛和公牛;公牛要么喂食全混合日粮，要么喂食即兴浓缩物。当比较所有性别饲喂全混合日粮时，公牛平均每天排放最多的肠道甲烷为 269.53 克，而小母牛和阉牛分别产生 237.54 克和 253.26 克。甲烷性状存在品种差异，平均而言，利穆赞在所研究的品种中产生的甲烷量最少。Herefords 和 Montbéliardes 每天产生的甲烷分别比 Limousins 多 124.50 克和 130.77 克。最有效的 10% 测试日记录，定义为与能量摄入和活重无关的每日甲烷排放量，比每日甲烷平均排放量（与能量摄入和活重无关）的动物平均减少 54.60 g/d。这相当于在相同的采食量和活重下，在 120 天的育肥期内，每头动物的甲烷产量减少了 6.5 公斤。