Animal science meets agricultural practice: Preliminary results of an innovative technical approach for exhaled breath analysis in cattle under field conditions

In human and veterinary medicine, the search for exhaled volatiles as potential markers for disease detection has gained increasing attention because exhaled breath analysis bears the advantages of being continuous, non-invasive and reveals instantly available results. The aim of this study was to introduce a technical set-up for breath analysis in bovines. The technical set-up allows (i) CO2-controlled sampling and preconcentration of alveolar gas and (ii) direct breath gas analysis via proton transfer reaction time-of-flight mass spectrometry (PTR-ToF-MS) in parallel. While alveolar gas sampling enables the analysis by gas chromatography-mass spectrometry for unequivocal substance identification, PTR-ToF-MS ensures real-time identification of confounding signals within one measurement. Applicability of the system to conscious cattle and reliability of the signals obtained under field conditions were tested at eight dairy farms. This first testing phase in veterinary practice confirmed that the set-up was well tolerated by each of the cows and that reliable measured values (i.e., raw data) were gained at different respiratory rates. Inspiration could be clearly distinguished from expiration, thus providing the basis for excluding ambient air contamination. Consecutive measurements under standardised conditions in two bovines aged 5–6 months revealed effects of time of day, food intake and handling that need to be evaluated in-depth in future studies with larger groups of animals. As result of these proof-of-concept trials, the introduced technical set-up can be recommended for future studies evaluating exhaled markers in cattle. Breath gas analysis offers a new research area in veterinary medicine and is one step forward towards refining large animal studies, even under field conditions.