Ruminal temperature may aid in the detection of subacute ruminal acidosis.

The objective of this study was to investigate the relationship between ruminal pH and ruminal temperature and to develop a predictive equation that can aid in the diagnosis of subacute ruminal acidosis (SARA). Six rumen-fistulated lactating Holstein dairy cows (639 +/- 51 kg body weight) were used in the study. Cows were randomly allocated to 1 of 2 dietary treatments: control (% of dry matter, 40% corn silage, 27% mixed haylage, 7% alfalfa hay, 18% protein supplement, 4% ground corn, and 4% wheat bran) or SARA total mixed ration (% of dry matter, 31% corn silage, 20% mixed haylage, 5% alfalfa hay, 15% protein supplement, 19% ground wheat, and 10% ground barley) and were fed daily at 0700 and 1300 h. The experiment consisted of 1 wk of adaptation followed by 1 wk of treatment. Ruminal pH and ruminal temperature were simultaneously and continuously recorded every minute for 4 d per week using the same indwelling electrode. Subacute-acidotic cows spent more time (min/d) below ruminal pH 5.6 and a greater time above 39.2 degrees C than control cows. Ruminal pH nadir had a negative relationship with its corresponding ruminal temperature (R2 = 0.77). Therefore, ruminal temperature may have potential to predict ruminal pH and thus aid in the diagnosis of SARA.