Browsing by Person "Eichinger, Julia"

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Describing the metabolic status of dairy cows using exhaled breath
(2024) Eichinger, Julia; Huber, Korinna
The steadily increased milk yield in high-yielding dairy cows during early lactation results in high energy demands that exceed energy intake, leading to the mobilization of body tissue reserves and a greater susceptibility to metabolic and inflammatory diseases. Therefore, a reliable assessment of metabolic disorders and metabolic status is crucial for maintaining animal health and productivity on dairy farms and for understanding underlying metabolic processes in research. Current methods involve invasive sampling of blood and ruminal fluid, as milk characteristics lack sufficient sensitivity. Analyzing exhaled VOC of dairy cows could be a promising, non-invasive alternative, reflecting the cows` metabolic status due to variations of VOC influenced by endogenous metabolic processes. The present work, which has been published or submitted for peer-reviewed publications, discusses investigations regarding the applicability of exhaled VOC in describing the metabolic status of dairy cows. The first step forward involved detailed elaboration of the current challenges in this research field in a broad context. These challenges include the absence of an appropriate, established sampling setup due to the risk of sampling ambient or technically derived VOC, in addition to the low concentration and susceptibility to losses of cows’ endogenous exhaled VOC. This has led to significant gaps in understanding the physiological relevance of exhaled VOC, compounded by issues in VOC data analysis, the identification of discriminatory VOC, and linking them to their underlying pathways. To address and overcome these challenges, this work resulted in the development of an optimized sampling setup for exhaled VOC from dairy cows using polymer-based SPE cartridges, followed by our key strategies for sample preparation, storage, and analysis. This technical setup and strategies as a prerequisite, the physiological relevance of exhaled VOC was investigated in depth. Several key strategies were devised for this purpose. During data analysis, correction for multiple testing and consideration of performance parameters were deemed crucial. The selection of discriminatory VOC relied on criteria with appropriate thresholds that could be applied in combination. VOC identification was based on criteria aimed at minimizing misidentification while ensuring standardized procedures. Through the application of these strategies, we were able to confirm the usability of exhaled VOC for describing diet-induced metabolic status, along with a high number and concentration of identified VOC from exhaled breath compared to those from other biological matrices. Moreover, the high physiological relevance of exhaled VOC was confirmed by the identification of their underlying pathways and new potential biomarkers for describing the metabolic status of fat catabolism in the context of energy deficiency in dairy cows. Furthermore, this work sets the stage for optimizing exhaled VOC sampling for untargeted analysis and facilitating the identification of new potential biomarkers. This was achieved by using synthetic air as the inhalation source for dairy cows to minimize interferences with environmental VOC and by the selection of the appropriate SPE cartridge for exhaled VOC sampling based on our indicated selection criteria. Additionally, this work outlined how the findings can be applied as a targeted approach to the routine, non-invasive assessment of the metabolic status of dairy cows on practical farms, especially in the context of fat catabolism during energy deficiency. This could be achieved through the use of electronic noses conditioned to detect acetone and fatty aldehydes, which were identified as potential new biomarkers within this work.