The hand-held laser methane detector (LMD) technique has been suggested as an alternative method for measuring methane (CH4) emissions from enteric fermentation of ruminants in the field. This study aimed to establish a standard procedure for using LMD to assess CH4 production in cattle and evaluate the efficacy of the protocol to detect differences in CH4 emissions from cattle fed with diets of different forage-to-concentrate (FC) ratios. Experiment 1 was conducted with four Hanwoo steers (584 ± 57.4 kg body weight (BW)) individually housed in metabolic cages. The LMD was installed on a tripod aimed at the animal's nostril, and the CH4 concentration in the exhaled gas was measured for 6 min every hour for two consecutive days. For the data processing, the CH4 concentration peaks were identified by the automatic multi-scale peak detection algorithm. The peaks were then separated into those from respiration and eructation by fitting combinations of two of the four distribution functions (normal, log-normal, gamma, and Weibull) using the mixdist R package. In addition, the most appropriate time and number of consecutive measurements to represent the daily average CH4 concentration were determined. In Experiment 2, 30 Hanwoo growing steers (343 ± 24.6 kg BW), blocked by body weight, were randomly divided into three groups. Three different diets were provided to each group: high FC ratio (35:65) with low energy concentrate (HFC-LEC), high FC ratio with high energy concentrate (HFC-HEC), and low FC ratio (25:75) with high energy concentrate (LFC-HEC). After ten days of feeding the diets, the CH4 concentrations for all steers were measured and analyzed in duplicate according to the protocol established in Experiment 1. In Experiment 1, the mean correlation coefficient between the CH4 concentration from respiration and eructation was highest when a combination of two normal distributions was assumed (r = 0.79). The most appropriate measurement times were four times, two hours and one hour before, and one hour and two hours after morning feeding. Compared with LFC-HEC, HFC-LEC showed 49% and 57% higher CH4 concentrations in exhaled gas from respiration and eructation, respectively (P < 0.01). In conclusion, the LMD method can be applied to evaluate differences in CH4 emissions in cattle using the protocol established in this study.

中文翻译：

---

手持式激光甲烷检测仪在集约化养殖牛肠道甲烷排放测量中的应用

手持式激光甲烷检测器 (LMD) 技术已被建议作为测量田间反刍动物肠道发酵产生的甲烷 (CH4) 排放的替代方法。本研究旨在建立使用 LMD 评估牛 CH4 产生的标准程序，并评估该协议的有效性，以检测饲喂不同草料与浓缩物 (FC) 比例的牛的 CH4 排放差异。实验 1 是用四头 Hanwoo 阉牛（584 ± 57.4 公斤体重 (BW)）单独饲养在代谢笼中进行的。将 LMD 安装在瞄准动物鼻孔的三脚架上，连续两天每小时测量 6 分钟呼出气体中的 CH4 浓度。对于数据处理，CH4 浓度峰由自动多尺度峰检测算法识别。然后通过使用 mixdist R 包拟合四个分布函数中的两个（正态、对数正态、伽马和 Weibull）的组合，将峰分离为呼吸和发出的峰。此外，还确定了代表每日平均 CH4 浓度的最合适的时间和连续测量次数。在实验 2 中，30 头 Hanwoo 生长阉牛 (343 ± 24.6 kg BW)，按体重划分，随机分为三组。向每组提供三种不同的饮食：高 FC 比例 (35:65) 和低能量浓缩物 (HFC-LEC)、高 FC 比例和高能量浓缩物 (HFC-HEC) 以及低 FC 比例 (25:75) 和高能浓缩物（LFC-HEC）。经过十天的饮食喂养，根据实验 1 中建立的方案，一式两份测量和分析所有牛的 CH4 浓度。在实验 1 中，当假定两个正态分布的组合时，呼吸和打嗝产生的 CH4 浓度之间的平均相关系数最高 (r = 0.79）。最合适的测量时间是早上喂奶前两小时和一小时，以及早上喂奶后一小时和两小时四次。与 LFC-HEC 相比，HFC-LEC 的呼吸和呕出气体中的 CH4 浓度分别高出 49% 和 57% (P < 0.01)。总之，LMD 方法可用于使用本研究中建立的协议评估牛 CH4 排放量的差异。