Short communicationA note on the effect of a palatable food reward on operant conditioning in horses
Introduction
Operant conditioning is often employed in the management of horses where a trainer uses positive and negative reinforcers to encourage a horse to perform the desired behavioural response. A positive reinforcer (e.g. food) is used after the desired behavioural response, whereas a negative reinforcer (e.g. pain) is removed when the animal performs the desired behavioural response (Waran et al., 2002). Successful training could influence horses’ utility and economic value, and it is, also, important for the welfare of horses to investigate the effect of positive, rather than negative reinforcers. However, there are only limited scientific studies on operant conditioning in horses and further research in this area is required (Nicol, 2002). Currently only a few studies relating to positive reinforcement (Myers and Mesker, 1960) and primary reinforcers (e.g. food, Houpt et al., 2004) for horses have been conducted.
In this study, we used a pelleted concentrate and cut timothy hay as food rewards during operant conditioning. The pelleted concentrate used in this study contained molasses, for which horses have a preference over timothy hay (Thorne et al., 2005). Therefore, we hypothesized that pelleted concentrate might be a palatable food and, as a reward, have a greater beneficial effect on operant conditioning compared to cut timothy hay. In our first experiment we investigated the effect of the palatability of the food reward on the time required to complete an operant conditioning task. It has been suggested that, during operant conditioning, animals can learn to have an expectation that pushing a button leads to a food reward (Toates, 2004). In our second experiment, we investigated the effect of changing the food reward, after the initial operant conditioning had been completed, on the operant responses of the horses. It was hypothesized that the change of reward would affect the horses’ expectation that had been induced by the operant conditioning and change their response rates.
Section snippets
Animals and management
Twelve thoroughbred female horses ranging from 2 to 5 years old (2 years old: n = 3; 3 years old: n = 4; 4 years old: n = 3; 5 years old: n = 2) were used at the Equine Research Institute of the Japan Racing Association in Utsunomiya, Japan. They were kept individually in box stalls (3.6 m × 5.2 m). They were turned out into a pasture or a paddock from 09:00 h to 13:00 h. Each received a pelleted concentrate and oat mixture (2.75 kg, fresh weight) and cut alfalfa hay (300 g, fresh weight) at 06:00 h and 16:00 h,
Experiment 1
There was no difference in the mean time needed to complete the operant conditioning between the two groups of horses (P: 46.6 min (S.E. 14.6), H: 41.3 min (S.E. 10.8), t = 0.29, P = 0.78) or in the mean number of rewards obtained during operant conditioning (P: 230.3 (S.E. 51.6), H: 137.7 (S.E. 18.8), t = 1.69, P = 0.12).
Experiment 2
Fig. 1 shows the number of rewards obtained in Groups P and H on the 5 days. In Group P, there was a difference in the mean number of rewards obtained among the 5 days (ANOVA: F4,16 =
Discussion
The pelleted concentrate used in this study contained molasses, for which horses have a preference over timothy hay (Thorne et al., 2005). Moreover, as our two experiments were held after the horses had eaten timothy hay, it might be expected that horses would be more motivated to eat the pelleted concentrate than the hay because it is said that horses are motivated to eat a variety of foods (Ninomiya et al., 2004, Thorne et al., 2005). It has been also reported that horses pressed a panel for
Conclusions
Hay appeared to motivate horses to perform an operant response less than pelleted concentrate. However, there was no difference between hay and pelleted concentrate in the time it took to train the horses to perform the operant response. For horses trained with a palatable food, a change to one that is less palatable may induce frustration, resulting in extinction of, or at least a severe decrease in the operant response in some horses. It would appear to be important to consider the
Acknowledgement
We thank the staff of the Equine Research Institute, Japan Racing Association, for their support during this study.
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