A standard protocol for fecal pH measurement in the horse

Fecal pH is a commonly used response variable in equine nutrition studies focused on evaluating gastrointestinal health. Although a relatively simple measurement, there is a lack of standardization in fecal-pH measurement protocols and a potential to improve precision of detection of differences between treatment groups. The objectives of this study were to measure fecal pH in collected feces using a range of different ratios with distilled water and allowing for different periods of time for equilibration, and to describe a simple fecal-pH measurement protocol to improve the knowledge gained from measuring fecal pH by decreasing measurement variation and standardizing the protocol across studies. Results indicate that addition of distilled water and the amount of time allowed for equilibration influence both measured pH and variation around the mean (P < 0.05). A protocol is described using fecal liquid without the addition of distilled water to measure fecal pH. Use of this approach results in less variation and a decrease in the number of animals needed per treatment group to detect small significant differences in fecal pH.