Measuring rumen pH and temperature by an indewelling and wireless data transmitting unit and application under different feeding conditions

Subacute rumen acidosis is a common and economically important herd health problem of dairy cattle and there is a crucial need for monitoring systems. Therefore an indwelling wireless data transfer system for monitoring rumen ph and temperature was assembled. Measurement times were user selectable, in our trials measurements were taken every 30 minutes. Stored data were transmitted to an external receiver using ISM-Band (433 mHz). The system was controlled by a microprocessor. Data (pH, temperature) were sampled with an Analog to Digital converter (A/D converter) and stored in an external memory chip. The external receiver was connected with a PC (USB) and results were analysed by software and displayed. The indwelling system could be administered orally, but to service the measuring units, described experiments were conducted using 5 ruminally cannulated steers. After calibrating by using standardized pH-dilutions and check for proper operation, rumen-pH und temperature measures were carried out under different feeding conditions. In feeding experiment 1, 100 % roughage (hay) ad. lib. was given to the animals for 1 week, measurements with the pH-monitoring unit were taken for 3 days. In feeding experiment 2, animals had daily pasture (from 4.30 a.m. to 16:30 p.m.) and forage ad lib. (from 17:00 p.m. to 4:00 a.m.) for 3 weeks. Measurements of rumen pH and temperature were carried out for the last 7 days. In feeding experiment 3, animals received a diet containing roughage: concentrate 50:50 for 7 days, measurements of rumen pH and temperature were taken for a period of 3 days. Statistical analysis was conducted using GLM (Statgraphic Plus 5.1) and Bonferroni-Holm-Test. In feeding experiment 1, rumen temperature (mean 38.40 70° C) was influenced significantly by drinking water but it is not connected with feeding time. Mean pH was 6.49 39 and nadir was pH 6.14. In feeding experiment 2, mean rumen temperature was 38.12 80° C and mean pH was 6.36 22. Nadir during pasture was pH 5.34, nadir during feeding roughage was 6.16. Pasture had a significant influence on rumen pH. In feeding experiment 3, mean rumen temperature was 38.55+/-0.83 deg C and mean pH was 6.37+/-0.24. Nadir was pH 5.29. Decline of rumen pH was significantly related to the feeding of concentrate. When comparing results of measuring standardized dilutions (pH 4, pH 7) prior and after in vivo measurements, coefficient of correlation was 0.9987 (mean for all probes). Drift pH 4 was 0,197 +/- 0,070 and drift pH 7 was 0,107 +/- 0,088. Time (%) below pH 5.5 was 0 in feeding trial 1, 12.1% in feeding trial 2 and 3% in feeding trial 3. Time (%) below ph 5.8 was 0 in feeding trial 1, 18.9% in feeding trial 2 and 16.6% in feeding trial 3. Time (%) below pH 6.2 was 55.6% in feeding trial 1, 44.2% in feeding trial 2 and 53.5% in feeding trial 3. Maximum duration of measurement is up to 40 days, then a service (energy) of probes is necessary, transmission of data was trouble free. Results indicate that the present method is a useful and proper tool for scientific applications, especially for a better understanding and defining of rumen acidosis. As the measuring system can also be administered to uninjured cattle, an adapted rumen pH measuring system will also be assembled for practical purposes in future.