May 1, 2009

A diet rich in fat may help to reduce stress in horses and cut the risk of accidents, according to research from the University of Cordoba in Spain.

Dr Alberto Jose Redondo and others compared the behaviour of horses fed a standard starch/sugar-based diet with those fed a diet with a higher fat content.

The only difference between the diets was in the amount of starch, sugar and fat that they contained. One, the conventional diet, based on sugar and starch, contained 3% fat. The second diet contained 10% fat. The overall digestible energy content was the same in each diet, as was the vitamin and mineral content.

Equine Science Update reports that the two groups of horses were fed one diet exclusively for two months. Then the horses were assessed individually, both at rest and when startled, to see if their behaviour differed according to the diet they had been eating.

The diets were then switched so that each horse received the other diet. Two months later the behavioural assessments were repeated.

To measure "stress", the researchers recorded heart rate and monitored blood cortisol levels.

Measurements were taken at rest. Then the horses were startled using a "jack-in -the-box" in which a tiger's head model mounted on a spring was released suddenly. Each horse's reaction was recorded on videotape so that the researchers could measure details such as the distance the horse's head moved when startled and the time taken.

Horses were fed the fat diet had lower resting cortisol levels, and showed reduced responses to being startled. When startled they did not move as far, and spent less time moving away. They also showed a smaller increase in heart rate in response to the startle test.

However, reaction time - the time between the release of the tiger head model and the horse's response - was not affected by the diet. So horses were able to respond immediately to the "threat" even though their responses were different.

Writing in the Journal of Applied Animal Behaviour Science, the authors point out the important implications of their work - both for horse welfare and for risk of injury to humans.

"Our results suggest that the use of a moderate fat-rich diet, according to the composition used in this study, may be an appropriate recommendation for maintaining horses in a low level of stress and risk of accidents."

Fat diet reduces stress and intensity of startle reaction in horses.
AJ Redondo, J Carranza, P Trigo.
Applied Animal Behaviour Science (2009) 118, 69 - 75.