Utilizing fecal pH to predict cecal pH in the equine

Abstract Text: Cecal cannulation is commonly used for direct assessment of dietary manipulation on cecal pH in equines. However, analysis of fecal material is considered one of few viable methods for monitoring digestive health in intact horses. In this retrospective study, we assessed the association between fecal pH and cecal pH in an attempt to develop a predictive equation for cecal pH. Nine cecally cannulated Quarter horses were utilized. The group was comprised of 5 geldings and 4 mares, between the ages of 8 to 10 yrs and body weight ranging from 455 and 590 kg. Horses were housed in heated individual stalls with ad libitum access to water and white salt blocks. Horses were fed 1.5% BW prairie grass hay split into twice daily feedings (0700 and 1830) and 0.5% BW concentrate (Omolene 200, Purina Animal Nutrition, LLC, Gray Summit, MO) which was fed in the mornings only (0700). Horses were maintained on this diet for 3 separate 21-d periods. Cecal and fecal pH were measured on d 19 to 21 of each period at -1, +1, +4, +8, +12, +16, +20, and +24 h relative to feeding the concentrate meal. Given inherent animal-to-animal variability in the pH dynamics of the cecum and rectum over time, the minimum cecal pH after feeding was collected for each animal-day combination and modeled as a function of the corresponding minimum fecal pH using a general linear mixed model. Analysis revealed evidence for an association (P= 0.03) between minimal cecal pH and minimal fecal pH. The estimated rate of change for minimum cecal pH per unit increase in minimum fecal pH was 0.131 with 95% confidence interval [0.011, 0.251]. The prediction equation for estimated cecal pH was Y = 0.131*X + 5.8969, where X is the observed fecal pH. However, the amount of predictive variability was considerable, likely due to multiple factors contributing to cecal pH, including feed composition, animal weight, and physiological state, which can alter the transit time of digesta from cecum to rectum. Our data indicates that fecal pH appears to have limited usefulness in predicting cecal pH.

Keywords: cecal pH; equine; fecal pH