Stability of rumen pH measurements obtained postmortem

Seventeen 350 lb (159 kg) Holstein steers were utilized to determine stability of rumen pH postmortem. Cattle were randomly assigned to two whole-corn ration treatment groups: (1) limit-fed (7.5 lb; 3.4 kg) or (2) fed ad libitum (9.5 lb; 4.3 kg). Calves were humanely euthanized, rumen fluid was collected, and pH measurements were taken at 0, 1, 2, 3, 6, 12, and 24 hours postmortem. A subset of five rumen samples per treatment at each sampling time was collected for later analysis of volatile fatty acid (VFA) content. No significant time by feeding regimen interactions were noted. The average postmortem rumen pH of calves fed ad libitum (5.7) was significantly lower than cattle limit-fed (6.2; P=0.03). The pH of rumen content increased for the first six hours postmortem, then gradually decreased over the next 18 hours back to initial pH readings (P<0.01). Rumen fluid total VFA concentrations tended to increase over time (P=0.06). Rumen fluid acetate concentration significantly increased (P<0.05), and proprionate concentrations tended to increase over time postmortem (P<0.08). These data indicate that postmortem ruminal pH could be a helpful diagnostic tool when used in conjunction with a complete necropsy.