Kazunori Ito

Technical note: development and testing of a radio transmission pH measurement system for continuous monitoring of ruminal pH in cows.

An indwelling ruminal pH system has been used for the continuous recording of ruminal pH to evaluate subacute ruminal acidosis (SARA) in dairy cows. However this system does not allow the field application. The objective of this study was to develop a new radio transmission pH measurement system, and to assess its performance and usefulness in a continuous evaluation of ruminal pH for use on commercial dairy farms. The radio transmission pH measurement system consists of a wireless pH sensor, a data measurement receiver, a relay unit, and a personal computer installed special software. The pH sensor is housed in a bullet shaped bolus, which also encloses a pH amplifier circuit, a central processing unit (CPU) circuit, a radio frequency (RF) circuit, and a battery. The mean variations of the measurements by the glass pH electrode were +0.20 (n=10) after 2 months of continuous recording, compared to the values confirmed by standard pH solutions for pH 4 and pH 7 at the start of the recording. The mean lifetime of the internal battery was 2.5 months (n=10) when measurements were continuously transmitted every 10 min. Ruminal pH recorded by our new system was compared to that of the spot sampling of ruminal fluid. The mean pH for spot sampling was 6.36 ± 0.55 (n=96), and the mean pH of continuous recording was 6.22 ± 0.54 (n=96). There was a good correlation between continuous recording and spot sampling (r=0.986, P<0.01). We also examined whether our new pH system was able to detect experimentally induced ruminal acidosis in cows and to record long-term changes in ruminal pH. In the cows fed acidosis-inducing diets, the ruminal pH dropped markedly during the first 2h following the morning feeding, and decreased moreover following the evening feeding, with many pulse-like pH changes. The pH of the cows showed the lowest values of 5.3-5.2 in the midnight time period and it recovered to the normal value by the next morning feeding. In one healthy periparturient cow, the circadian changes in ruminal pH were observed as a constant pattern in the pre-parturient period, however that pattern became variable in the post-partum period. The frequency of the ruminal pH lower than 5.5 increased markedly 3 and 4 days after parturition. We demonstrated the possible application of a radio transmission pH measurement system for the assessment and monitoring of the ruminal pH of cows. Our new system might contribute to accurate assessment and prevention of SARA.

A radio transmission pH measurement system for continuous evaluation of fluid pH in the rumen of cows

We developed a novel wireless radio transmission pH measurement system to continuously monitor ruminal bottom pH in cows, and compared these measurements to pH values determined by a spot-sample method. The wireless system consists of a pH sensor, data measurement receiver, relay unit, and personal computer with special software. The bullet-shaped sensor can be easily administered orally via a catheter into the rumen, without surgery. The glass electrode, using a temperature compensation system, can detect the rumen fluid pH with high accuracy. The ruminal bottom pH in healthy rumen-fistulated cows was measured as 6.52 ± 0.18 by the wireless system and as 6.62 ± 0.20 by the spot-sample method; with a correlation between pH measurements using these different methods (n = 8, 24 samples, r = 0.952, P < 0.01). When measured serially in a cow fed a diet evoking rumen acidosis, the ruminal bottom pH decreased markedly following the morning feeding and then increased gradually by the next morning feeding. This wireless system is a ready-to-use tool for estimating circadian changes in ruminal bottom pH.