Technical note: Evaluation of a continuous ruminal pH measurement system for use in noncannulated small ruminants

The objective of this study was to evaluate the precision and accuracy of an indwelling ruminal pH measurement system that could be used in small ruminants (small ruminant ruminal pH measurement system; SRS) without requiring ruminal cannulation. The outer diameter, length, and weight of the SRS were 20.6 mm, 138 mm, and 245 g, respectively. This device was capable of logging pH, temperature, and battery voltage. In Exp. 1, a ruminally cannulated sheep (94 kg) was infused with a 40% (wt/vol) glucose solution to supply 5 g of glucose/kg of BW into the rumen. Ruminal pH was recorded every 30 s simultaneously using a portable pH meter and the SRS. In Exp. 2, 30 noncannulated sheep (72 +/- 10 kg of BW) were orally administered with a 40% glucose solution as described above (5 g of glucose/kg of BW; n = 22) or an equivalent volume of water (12.5 mL/kg of BW; n = 8). Sheep were slaughtered 3 h after the oral drench, and immediately after slaughter ruminal pH readings were measured manually using a portable pH meter and were compared with measurements recorded by the SRS. In Exp. 1, the relationship between manual pH measurement using a portable pH meter and the SRS (226 data pairs) had a Pearson correlation coefficient and concordance correlation coefficient of 0.97 and 0.96, respectively. Furthermore, the scale shift and location shift observed in Exp. 1 were 1.28 and 0.00, respectively. The relationship between measurements conducted manually using a portable pH meter and the SRS in Exp. 2 had Pearson and concordance correlation coefficients of 0.96 and 0.95, respectively. The respective scale and location shifts for Exp. 2 were 1.16 and 0.04. These results indicate that the measurements obtained from SRS were in agreement with simultaneous measurements manually conducted using a portable pH meter, suggesting that the SRS can be used to measure ruminal pH in noncannulated small ruminants.