Taking the Bitter with the Sweet - A Preliminary Study of the Short-Term Response of Horses to Various Tastants in Solutions

Horses can distinguish sweet, salty, sour, and bitter tastes, but little is known about their preferences for various tastants. Understanding horse taste preferences can aid in increasing water intake by adding a preferred tastant or by masking an unpleasant taste to encourage administration of medications, for example. The quantity of water intake by horses was examined over five separate trials involving a two-choice preference test between tap water and water containing varying concentrations of sucrose (0-50g/100ml), citric acid (0-2.43mg/100ml), quinine (0-30mg/100ml) or a mix of sucrose (10mg/100ml)/citric acid (1.31mg/100ml) and sucrose (10mg/100ml)/quinine (20mg/100ml). Horses (n = 5) showed a weak preference for sweetened water up to 10mg/100ml (p < .001), with a rejection at higher concentrations. Horses rejected all concentrations of both sour (n = 12 horses; p < .001) and bitter (n = 6 horses; p < .001) solutions. In the mixed tastant trials, sucrose mixed with citric acid was only weakly rejected compared to the sucrose solution alone, which was moderately rejected (n = 5 horses; p < .001). Similarly, mixed sucrose/quinine solution intake increased over the quinine solution alone (n = 9 horses; p < .001). There was a large variation among individual horses within each trial, with some horses strongly rejecting sucrose solutions and others strongly preferring citric acid solutions. No horse indicated a preference for bitter solution in any trial. Age (p < .001), breed (p < .001), and exercise (p = .004) all influenced total fluid intake in the sour trial, not dependent on treatment (p = .063). These preliminary results show that some horses appear to prefer sweet and a preferred tastant can mask a less preferred tastant.