The lower the pH of the water, the less the horses will consume.
Preferred flavors added to food, water, or medications my possibly increase palatability and intake. Although there is some research on certain flavors such as sour, peppermint, and banana, little evidence exists measuring the taste preferences of horses. Researchers at the University of Guelph set out to determine the horse preference or aversion to sourness through alteration of water pH.
Twelve horses were used for the study. All horses received daily turnout with free access to forage and water. Each horse was given a treatment for four consecutive days. Treatments were fed in identical black buckets and consisted of control water (pH 7.5) and control water plus citric acid with either a pH of 5.0, 3.6, or 2.9 (the lower the pH, the more acidic the water). Citric acid is sometimes used to flavor water for horses. Water buckets were refilled and weighed as necessary to determine total amount of water consumed from each bucket. Treatment intake was calculated as the percentage of total daily fluid intake, and these values were used to determine preference.
Preference and aversion were established as percent intake above 60% and below 40%, respectively. Differences of intake were noted in the buckets with a pH of 3.6 and 2.9 (these groups did not differ from each) whereas a pH of 5.0 was moderately aversive and tended to differ from the control bucket, which the horses most preferred. Although acidic treatments were found to be aversive, no treatment was completely rejected by the horses. However, the buckets with a pH of 2.9 were the least preferred.
In conclusion, the lower the pH of the water the less the horses will consume.