Effects of sensor location during in situ measurements on pH in caecal digesta of the horse,and post-observational treatment of sensor data

Measurements of caecal pH are useful when studying the effect of a ration on the hindgut environment in horses. Frequent in situ measurements of caecal pH have been used to measure short-term changes in pH. However, this method also results in a large and complex data set. Transient random influxes of alkaline content from the small intestine might result in short-time elevations in caecal pH that complicates data processing. We used two caecal-cannulated horses fed two different rations in a cross-over design experiment. We compared frequent in situ measurements of caecal pH measured with an unweighted and a weighted pH electrode. Based on our results, we recommend to use a weighted pH electrode situated in the deeper layers of the caecum compared to an unweighted. If an unweighted electrode is used, we present a peak-detecting algorithm to eliminate short-time elevation peaks caused by the ileal influx.