Context Research into improving feed efficiency by ruminant animals grazing pastures has historically been restrained by an inability to measure feed intake by large numbers of individual animals. Recent advances in portable breath measurement technology could be useful for this purpose but methodologies need to be developed. Aims To evaluate predictive models for metabolisable energy intake (MEI) by free-ranging cattle using multiple short-term breath samples and then apply these to predict MEI by free-ranging cattle in a historic grazing experiment with cattle genetically divergent for residual feed intake (feed efficiency). Methods Predictive models for MEI were developed using bodyweight (BW) data, and carbon dioxide production rate (CPR) and methane production rate (MPR) from multiple short-term breath measurements, from an experiment with long-fed Angus steers on a grain-based diet, and an experiment with short-fed Angus heifers on a roughage diet. Heat production was calculated using CPR and MPR. Energy retained (ER) in body tissue gain by steers was calculated from BW, ADG, initial and final subcutaneous fat depths, and for both groups using feeding-standards equations. Key results Metabolic mid-test BW (MBW) explained 49 and 47% of the variation in MEI in the steer and heifer experiment, respectively, and for the steers adding ADG and then subcutaneous fat gain resulted in the models accounting for 60 and then 65% of the variation in MEI. In the steer experiment, MBW with CPR explained 57% of the variation in MEI, and including MPR did not account for any additional variation. In the heifer experiment, MBW with CPR explained 50%, and with MPR accounted for 52% of the variation in MEI. Heat production plus ER explained 60, 35 and 85% of the variation in MEI in the steer and the heifer experiments, and in the pooled data from both experiments, respectively. Conclusions Multiple short-term breath measurements, together simple BW data, can be used to predict MEI by free-ranging cattle in studies in which animals do not have feed-intake or ADG recorded. Implications This methodology can be used for research into improving feed efficiency by farm animals grazing pastures.

中文翻译：

---

使用多个短期呼吸样本预测自由放养牛的代谢能量摄入并应用于牧场案例研究

背景 通过反刍动物放牧来提高饲料效率的研究历来受到无法测量大量个体动物的饲料摄入量的限制。便携式呼吸测量技术的最新进展可用于此目的，但需要开发方法。目的 使用多个短期呼吸样本评估自由放养牛的代谢能摄入量 (MEI) 预测模型，然后将这些模型应用于历史性放牧实验中自由放养牛的代谢能摄入量 (MEI) 预测模型，其中牛在剩余饲料摄入方面存在遗传差异。饲料效率）。方法 MEI 的预测模型是使用体重 (BW) 数据以及来自多次短期呼吸测量的二氧化碳产生率 (CPR) 和甲烷产生率 (MPR) 开发的，来自以谷物为基础的饮食的长期喂养安格斯公牛的实验，以及以粗饲料为基础的短期喂养的安格斯小母牛的实验。使用 CPR 和 MPR 计算热量产生。由体重、ADG、初始和最终皮下脂肪深度以及两组使用喂养标准方程计算出的身体组织增益中的能量保留 (ER)。主要结果 代谢中期测试 BW (MBW) 分别解释了公牛和小母牛实验中 MEI 变化的 49% 和 47%，对于公牛添加 ADG 然后皮下脂肪增加导致模型分别解释了 60 和 65 MEI 变化的百分比。在转向实验中，带有 CPR 的 MBW 解释了 MEI 中 57% 的变化，并且包括 MPR 并没有解释任何额外的变化。在小母牛实验中，带有 CPR 的 MBW 解释了 50%，并且 MPR 占 MEI 变异的 52%。产热加 ER 分别解释了公牛和小母牛实验以及两个实验的汇总数据中 MEI 变化的 60%、35% 和 85%。结论 在没有记录动物采食量或 ADG 的研究中，多个短期呼吸测量值和简单的 BW 数据可用于预测自由放养牛的 MEI。影响 该方法可用于研究通过放牧牧场的农场动物提高饲料效率。可用于在没有记录动物采食量或 ADG 的研究中通过自由放养的牛来预测 MEI。影响 该方法可用于研究通过放牧牧场的农场动物提高饲料效率。可用于在没有记录动物采食量或 ADG 的研究中通过自由放养的牛来预测 MEI。影响 该方法可用于研究通过放牧牧场的农场动物提高饲料效率。