Herd R M, Velazco J I, Arthur P F, Hegarty R F
J Anim Sci. 2016 Nov;94(11):4882-4891. doi: 10.2527/jas.2016-0613.
The objective of the study was to evaluate associations among animal performance and methane emission traits under feedlot conditions and in respiration chambers in Angus cattle bred to vary in residual feed intake (RFI), which is a measure of feed efficiency. Fifty-nine cattle were tested for feedlot RFI, of which 41 had methane production recorded on an ad libitum grain-based ration in the feedlot, 59 on a restricted grain-based ration in respiration chambers, and 57 on a restricted roughage ration in respiration chambers. The cattle became older and heavier as they went through the different phases of the experiment, but their feed intake (expressed as DMI) and daily emission of enteric methane (methane production rate; MPR) did not increase proportionally, as feed offered was restricted in the respiration chamber tests. Methane emissions by individual animals relative to their DMI were calculated as methane yield (MY; MPR/DMI) and as 2 measures of residual methane production (RMP and RMP), which were calculated as the difference between measured MPR and that predicted from feed intake by 2 different equations. Within each test regime, MPR was positively correlated ( = 0.28 to 0.61) with DMI. Phenotypic correlations for MY, RMP, and RMP between the feedlot test and the restricted grain test ( = 0.40 to 0.43) and between the restricted grain test and the restricted roughage test were moderate ( = 0.36 to 0.41) and moderate to strong between the feedlot test and the restricted roughage test ( = 0.54 to 0.58). These results indicate that the rankings of animals for methane production relative to feed consumed are relatively stable over the 3 test phases. Feedlot feed conversion ratio and RFI were not correlated with MPR in the feedlot test and grain-based chamber test but were negatively correlated with MPR in the chamber roughage test ( = -0.31 and -0.37). Both were negatively correlated with MY and RMP in the feedlot test ( = -0.42 to -0.54) and subsequent chamber roughage test ( = -0.27 to -0.49). Midparent estimated breeding values for RFI tended to be negatively correlated with MY and RMP in the feedlot test ( = -0.27 and -0.27) and were negatively correlated with MY, RMP, and RMP in the chamber roughage test ( = -0.33 to -0.36). These results showed that in young growing cattle, lower RFI was associated with higher MY, RMP, and RMP but had no significant association with MPR.
本研究的目的是评估在饲养场条件下以及在呼吸室内，安格斯牛的动物生产性能与甲烷排放性状之间的关联。这些安格斯牛因剩余采食量（RFI）不同而进行选育，RFI是饲料效率的一种衡量指标。对59头牛进行了饲养场RFI测试，其中41头在饲养场以随意采食的谷物型日粮记录了甲烷产量，59头在呼吸室内以限量的谷物型日粮进行测试，57头在呼吸室内以限量的粗饲料日粮进行测试。随着牛经历实验的不同阶段，它们变得更老、体重更重，但由于呼吸室测试中提供的饲料受到限制，它们的采食量（以干物质采食量表示）和肠道甲烷的日排放量（甲烷产生率；MPR）并未成比例增加。将个体动物的甲烷排放量相对于其干物质采食量计算为甲烷产量（MY；MPR/DMI）以及作为剩余甲烷产生量的两种度量（RMP和RMP），RMP和RMP是通过两种不同方程计算的实测MPR与根据采食量预测的MPR之间的差值。在每个测试方案中，MPR与干物质采食量呈正相关（= 0.28至0.61）。饲养场测试与限量谷物测试之间（= 0.40至0.43）以及限量谷物测试与限量粗饲料测试之间，MY、RMP和RMP的表型相关性为中等（= 0.36至0.41），饲养场测试与限量粗饲料测试之间为中等至强相关（= 0.54至0.58）。这些结果表明，相对于采食饲料的甲烷产量而言，动物的排名在3个测试阶段相对稳定。饲养场饲料转化率和RFI在饲养场测试和谷物型呼吸室测试中与MPR不相关，但在呼吸室粗饲料测试中与MPR呈负相关（= -0.31和-0.37）。在饲养场测试（= -0.42至-0.54）及随后的呼吸室粗饲料测试（= -0.27至-0.49）中，二者均与MY和RMP呈负相关。饲养场测试中RFI的中亲估计育种值与MY和RMP呈负相关（= -0.27和-0.27），在呼吸室粗饲料测试中与MY、RMP和RMP呈负相关（= -0.33至-0.36）。这些结果表明，在生长中的幼龄牛中，较低的RFI与较高的MY、RMP和RMP相关，但与MPR无显著关联。
