Irish Cattle Breeding Federation, Ballincollig, Co. Cork, Ireland.
Department of Biological Sciences, Munster Technological University, Bishopstown, Ireland.
J Anim Sci. 2024 Jan 3;102. doi: 10.1093/jas/skae034.
Genetic selection has been identified as a promising approach for reducing enteric methane (CH4) emissions; a prerequisite for genetic evaluations; however, these are estimates of the necessary genetic parameters based on a population representative of where the genetic evaluations will be used. The objective of this study was, therefore, to derive genetic parameters for a series of definitions of CH4, carbon dioxide (CO2), and dry matter intake (DMI) as well as genetic correlations between CH4, CO2, and DMI in a bid to address the paucity of studies involving methane emissions measured in beef cattle using GreenFeed systems. Lastly, estimated breeding values (EBV) were generated for nine alternative definitions of CH4 using the derived genetic parameters; the EBV were validated against both phenotypic performance (adjusted for non-genetic effects) and the Legarra and Reverter method comparing EBV generated for a subset of the dataset compared to EBV generated from the entire dataset. Individual animal CH4 and CO2 records were available from a population of 1,508 multi-breed growing beef cattle using 10 GreenFeed Emission Monitoring systems. Nine trait definitions for CH4 and CO2 were derived: individual spot measures, the average of all spot measures within a 3-h, 6-h, 12-h, 1-d, 5-d, 10-d, and 15-d period and the average of all spot measures across the full test period (20 to 114 d on test). Heritability estimates from 1,155 animals, for CH4, increased as the length of the averaging period increased and ranged from 0.09 ± 0.03 for the individual spot measures trait to 0.43 ± 0.11 for the full test average trait; a similar trend existed for CO2 with the estimated heritability ranging from 0.17 ± 0.04 to 0.50 ± 0.11. Enteric CH4 was moderately to strongly genetically correlated with DMI with a genetic correlation of 0.72 ± 0.02 between the spot measures of CH4 and a 1-d average DMI. Correlations, adjusted for heritability, between the adjusted phenotype and (parental average) EBV ranged from 0.56 to 1.14 across CH4 definitions and the slope between the adjusted phenotype and EBV ranged from 0.92 to 1.16 (expectation = 1). Validation results from the Legarra and Reverter regression method revealed a level bias of between -0.81 and -0.45, a dispersion bias of between 0.93 and 1.17, and ratio accuracy (ratio of the partial evaluation accuracies on whole evaluation accuracies) from 0.28 to 0.38. While EBV validation results yielded no consensus, CH4 is a moderately heritable trait, and selection for reduced CH4 is achievable.
遗传选择已被确定为减少肠道甲烷（CH4）排放的一种有前途的方法；这是遗传评估的前提条件；然而，这些都是根据将进行遗传评估的代表性群体估计的必要遗传参数。因此，本研究的目的是针对一系列 CH4、二氧化碳（CO2）和干物质摄入量（DMI）的定义得出遗传参数，以及 CH4、CO2 和 DMI 之间的遗传相关性，以解决涉及使用 GreenFeed 系统测量牛肉甲烷排放的研究不足的问题。最后，使用得出的遗传参数为 CH4 的九个替代定义生成了估计育种值（EBV）；根据表型表现（针对非遗传效应进行调整）和 Legarra 和 Reverter 方法对 EBV 进行了验证，该方法将数据集子集的 EBV 与整个数据集的 EBV 进行了比较。使用 10 个 GreenFeed 排放监测系统，从 1508 头多品种生长肉牛的群体中获得了单个动物的 CH4 和 CO2 记录。从 CH4 和 CO2 中得出了九个性状定义：个体点测量值、3 小时、6 小时、12 小时、1 天、5 天、10 天和 15 天内所有点测量值的平均值以及整个测试期间的所有点测量值的平均值（测试时的 20 至 114 天）。1155 头动物的 CH4 遗传力估计值随着平均时间的增加而增加，从个体点测量性状的 0.09±0.03 到整个测试平均值性状的 0.43±0.11；CO2 的估计遗传力也存在类似的趋势，范围从 0.17±0.04 到 0.50±0.11。肠道 CH4 与 DMI 中度至高度遗传相关，CH4 点测量值与 1 天平均 DMI 的遗传相关系数为 0.72±0.02。在调整了遗传力的情况下，CH4 定义之间的调整表型与（父母平均）EBV 的相关性从 0.56 到 1.14 不等，调整表型与 EBV 的斜率从 0.92 到 1.16（期望=1）不等。Legarra 和 Reverter 回归方法的验证结果显示，水平偏差在-0.81 到-0.45 之间，分散偏差在 0.93 到 1.17 之间，部分评估准确性与整体评估准确性的比率（整体评估准确性的部分评估准确性）在 0.28 到 0.38 之间。虽然 EBV 验证结果没有达成共识，但 CH4 是一个中度遗传的性状，并且可以实现减少 CH4 的选择。
