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A main problem in dairy herds is a unsatisfying heat detection and a subsequent decline of insemination rates and fertility. The aim of the present study is to evaluate if a change in the CO2-levels in breath of healthy dairy cows can be used as an indicator of their sexual stage. As shown previously for women, CO2-levels could be used to determine
the stage of the sexual cycle. In dairy cows reliable studies utilizing CO2-levels in breath correlated with the cycle stage are not available so far. Normal cycling or late pregnant cows were introduced into our study to investigate CO2-levels together with blood estradiol as well as progesterone concentrations. Two different handheld CO2-detectors
with different technologies were used and their suitability evaluated in practise.
Our first experiments clearly showed that the simple detector (CapnoWatch) developed for use in women does not meet scientific accuracy. Furthermore, a cumbersomely practice made it unsuitable to routinely measure CO2-contents in cows breath. Under such circumstance
a validation and reproducibility of generated data was only possible using another high sophisticated instrument. Preliminary data sets elaborated in late pregnant cows did not account for an obvious correlation between changing CO2-levels and the blood progesterone
concentrations. Finally our study will provide reliable data to assess the applicability of CO2-detection in breath of dairy cows on the way to predict the stage of their sexual cycle. If that techniques proves positive a rapid non-invasive cycle detection method would probably support an increased insemination success in dairy herds. Supported by