A comparison of demand for two different feeds with horses (Equus callabus)

Abstract

There are few studies with horses that examine either their food preferences or the use of increasing work requirements to assess their demand for food. The first experiment used Multiple-Stimulus-Without-Replacement procedure to measure six horses' preferences for four different feeds. From these, a high- (Yearling mix) and a low- (Rice) preference feed were selected. The horses were then exposed to two series of increasing fixed ratio (FR) schedules with each of two feeds, in fixed-length sessions. The overall response rates were bitonic, running response rates decreased and average post-reinforcement pauses increased with increases in fixed-ratio value, typical of previous research. Yearling mix maintained faster responding to higher fixed-ratio values for most horses than did Rice. The demand functions (i.e., the numbers of reinforcers obtained in a session as functions of the ratio size on double logarithmic coordinates) showed mixed elasticity for both Yearling mix and Rice (where there were enough data that a function could be sensibly fitted). There were lower levels of demand (i.e., number of reinforcers obtained) for Rice than Yearling mix at small fixed ratio values, the reverse of the findings reported previously for reinforcer size and preference value. It is suggested that this difference could have been the result of the open economic conditions of this study. However, the equation suggested by Hursh and Silberberg (2008) provided a good description of the data in this study, with Rice having a lower essential value that Yearling mix.