Sampling a cows breath
One of the most effective ways of diagnosing illness in cows is to use your nose. Ancient and modern stockmen and veterinarians routinely although sometimes unknowingly use their nose to detect ill health. I first became interested in the subject of diagnosing cow health conditions by breath analysis in the mid 1990s when reports of electronic noses first began to appear.
I wrote up the results in an Electronic nose to detect oestrus, but the main disadvantage to the polymer electronic nose arrays was their extreme sensitivity to water which of course saturates exhaled breath. With some clever engineering we were able to extract a signal from the water noise but this was never going to be a lightweight portable system.
We started using Infra-Red and FTIR machines for gas analysis from breath and calibrated this against absorption tube capture and GCMS analysis. Our main target was the Ketosis Risk Analysis 1999 which from time immemorial has been described as causing cows to exhale the smell of acetone. We would capture the breath into impermeable flexible bags by evacuating a rigid chamber around them and using one way valves so that clear samples could be taken.
We created both a portable and a static system. In the static system built into a feeder we got the cows to volunteer and donate a nasal sample by blowing into a tube with a reward of feed.
The main result we established was that the acetone concentration rose from about 4 ppm in a healthy cow to 8 ppm in a sub-clinically ketotic animal, although in practice it proved quite difficult to induce ketosis by feed manipulation alone. We also reported in Dimethyl sulfide emissions from livestock 2000 the hypothesis that breathing is a method for the cow to vent surplus sulphur with some interesting results.
The best device we found for measuring small concentrations of volatiles in exhaled breath was the T-SIFT machine which has an amazing range but was quite a static heavy device. Claire Turner has written up the results of using the system to measure precursors of tuberculosis in cow’s breath as we attempted to come up with a simple easy to use method that could replace the current TB test on farms.
However, the concept of using static samplers to collect breath was great fun and useful to make progress in the science. In practice there are easier ways of managing this condition and this led me to using wireless sensors to measure rumen pH directly, which is why eCow was established.