Barrientos-Blanco M A, Arshad U, Giannoukos S, Islam M Z, Kunz C, Peng R, Räisänen S E, Zenobi R, Niu M
Animal Nutrition, Institute of Agricultural Sciences, Department of Environmental Systems Science, ETH Zürich, 8092 Zürich, Switzerland.
Analytical Chemistry, Department of Chemistry and Applied Biosciences, ETH Zürich, 8093 Zürich, Switzerland.
JDS Commun. 2025 Mar 18;6(3):438-443. doi: 10.3168/jdsc.2024-0732. eCollection 2025 May.
Frequent eructation in ruminant animals results in an exhaled blend of ruminal eructed and breath volatile organic compounds (VOC). The physiological distinction between the gas sources can limit the applicability of breath metabolomics (or breathomics) in describing the metabolic phenotype of cows. The objective of this study was to establish a benchmark sampling method for collecting breath samples in dairy cows while they were not eructating. Twelve multiparous mid-lactation Holstein cows were enrolled to collect (1) breath (BR; bloodborne VOC exchanged at the lungs) and (2) ruminal exhaled (RE; a mixture of VOC from ruminal eructation and breaths during eructations) samples. Gas samples were collected using a head chamber (GreenFeed system) with real-time CH readings. By monitoring eructation events, a threshold of <150 mV CH was set to sample breath, and >250 mV was used to collect BR and RE. Both samples were analyzed using secondary electrospray ionization-high resolution MS (SESI-MS) and GC. Implementing CH as a marker resulted in 80% lower CH concentrations in BR compared with RE. Analysis using SESI-MS revealed a total of 324 and 242 features consistently identified across all periods of the study in [M-H] and [M+H] MS ion mode, respectively, for BR and RE. In BR, 18 features exhibited greater concentrations, whereas 8 had a tendency to have greater concentrations compared with RE. In contrast, RE revealed 51 features with greater concentrations, and 13 with a tendency for greater concentrations compared with BR. Ruminal VFA acetate, propionate, and butyrate were 20.9%, 27.4%, and 32.7% greater in RE compared with BR, respectively. Lower CH levels in BR and the greater VFA concentrations in the RE validated the ability of the method to differentiate breath from ruminal eructed VOC. Our study established a method to distinguish and separately collect BR and RE samples in dairy cows. This advance shows the potential to use breathomics as a reliable and noninvasive tool for metabolic assessments in ruminant research.
反刍动物频繁嗳气会呼出瘤胃嗳气和呼吸挥发性有机化合物（VOC）的混合气体。气体来源之间的生理差异可能会限制呼吸代谢组学（或呼吸组学）在描述奶牛代谢表型方面的适用性。本研究的目的是建立一种在奶牛不嗳气时采集呼吸样本的基准采样方法。选取12头经产中期泌乳的荷斯坦奶牛，采集（1）呼吸气（BR；在肺部交换的血源性VOC）和（2）瘤胃呼出气（RE；瘤胃嗳气和嗳气期间呼出的VOC混合物）样本。使用带有实时CH读数的头部腔室（GreenFeed系统）采集气体样本。通过监测嗳气事件，将<150 mV CH的阈值设定为采集呼吸气样本，>250 mV用于采集BR和RE。两种样本均使用二次电喷雾电离高分辨率质谱（SESI-MS）和气相色谱（GC）进行分析。以CH作为标志物，BR中的CH浓度比RE低80%。使用SESI-MS分析发现在[M-H]和[M+H]质谱离子模式下，整个研究期间BR和RE分别共鉴定出324个和242个特征峰。在BR中，18个特征峰浓度更高，而与RE相比，有8个特征峰有浓度更高的趋势。相比之下，RE显示出51个浓度更高的特征峰，13个与BR相比有浓度更高趋势的特征峰。瘤胃挥发性脂肪酸乙酸、丙酸和丁酸在RE中的含量分别比BR高20.9%、27.4%和32.7%。BR中较低的CH水平和RE中较高的挥发性脂肪酸浓度验证了该方法区分呼吸气和瘤胃嗳气VOCs的能力。我们的研究建立了一种区分并分别采集奶牛BR和RE样本的方法。这一进展表明呼吸组学有潜力作为反刍动物研究中可靠且无创的代谢评估工具。
