Motivation for hay: effects of a pelleted diet on behavior and physiology of horses.

This study aims to understand the diet preference of horses between hay and food pellets and its effect on their behavior and physiology. The researchers found that horses tended to prefer hay, and using food pellets in the diet signaled behavioral and physiological changes in the animals.

Study Objectives and Method

• The primary objective of this study was to determine horses’ preference and motivation between a high fiber diet (hay) and a low roughage diet (pelleted food) and its implications on their welfare.
• Eight mares were selected for the study and fed two types of diets on a counterbalanced order – orchard grass hay and a complete pelleted feed – with each trial lasting three weeks and a one-week transition period in between.
• To assess the horses’ motivation for each type of diet, they were trained to press a panel to receive a food reward. The number of presses, termed Fixed Ratio (FR), indicates the effort the horses were willing to exert to obtain either type of food.

Results and Findings

• The results demonstrated that horses displayed greater motivation for hay when they were fed a pellet diet.
• When fed hay, horses worked more (median FR of 25.5) to obtain pellets. Conversely, when provided with a pelleted diet, they were more motivated to access hay (FR of 13). However, they showed no effort to obtain additional hay when they were already on a hay diet (FR=0).
• Apart from a greater preference for hay, horses also spent significantly more of their time feeding on hay (61.5%) than on the pelleted diet (10%).
• The study also observed a change in the horses’ behavior, with 58% of their time standing when foddered with pellets compared to only 37% when fed with hay.
• They also searched for food more when provided a pellet diet, spending 11.5% of their day sifting through their surroundings compared to only 1.2% when on a hay diet.
• Horses were observed to chew more when eating a hay diet than when eating a pellet diet, which may imply that horses find hay more satisfying.
• Lastly, the research found a decrease in fecal pH in horses fed with the pelleted diet, indicating a physiological effect of the diet type on horses.

Conclusion

• This study shows a clear preference of horses for a high-fiber diet (hay) over a low-roughage diet (pellets), and its influence on their behavior and health.
• The findings suggest that feeding horses a low-roughage diet may compromise their welfare, considering their greater motivation for and time spent on consuming hay as well as their behavioral changes.