Evaluation of a device for continuous measurement of rumen pH and temperature considering localization of measurement and dietary concentrate proportion

Continuous rumen pH and temperature measurement may be useful tools for diverse purposes including the detection of subacute ruminal acidosis. The objectives of the present study were to evaluate a device for continuous monitoring of rumen pH and temperature of cattle focussing on rumen pH determination and to test the effects of measurement localization as well as dietary concentrate proportion on rumen pH and temperature. Four rumen-fistulated cows were fed on two diets containing 0 and 40 % concentrate. Measurement was executed for two days per cow and diet. One probe was inserted each in the dorsal and ventral rumen sac to measure pH and temperature. Manual temperature determination and pH measurement were performed postprandial in direct proximity to the probes at preset short term intervals. PH sensors were tested for drift. The pH sensor drift was inconsistent with a considerable individual variation. A moderate correlation between manual and continuous measurement of pH (r = 0.59, p <0.001) and temperature (r = 0.46, p <0.001) was calculated. A Bland-Altman comparison of both methods indicated moderate agreement. A bias effect of probe pH determination with a pH overestimation in the range of low rumen pH below 6.0 and an underestimation of higher rumen pH was observed. Rumen pH was not affected by the localization of measurement but by diet and time after feeding. Significant effects of localization, diet and time and an interaction of localization and diet on rumen temperature were found. In conclusion, the evaluated technique was promising. Indications of inaccuracy of probe pH measurement suggested the need of further improvement.