Manipulation of the intestinal microbiome is an emerging area of research, especially in hind-gut fermenters such as the horse. The aim of this study was to determine whether fecal pH can provide a simple and cost-effective tool to document changes in the intestinal metabolome and microbiome following supplementation of feed with an enzyme rich malt extract (ERME). Fecal pH was determined weekly in triplicate using a commercial soil pH meter in 72 Thoroughbred racehorses in training before and during supplementation with ERME (300mls per day divided into two feeds) alongside their regular feeding schedule. No control group was included. Fecal pH increased over the 4 weeks of treatment from 6.20 (6.15-6.24) to 6.40 (6.38-6.44; P<0.0001). Changes were not observed at one-week intervals but were apparent after 2 weeks There was a significant increase in the proportion of horses with a ‘normal’ pH at the end of the study (55%) compared to the start of the study (11%; p<0.001). These data support the further validation of the use of fecal pH in large scale microbiome/metabolome studies in the horse, although comparisons with these outcomes are now warranted.