What is a risk factor for dehydration in horses?

Dietary changes can significantly affect a horse's hydration status because they can alter the amount of water a horse consumes or needs. When a horse's diet changes, especially if it transitions to drier or more concentrated feeds, it may not drink enough water to compensate for the change in nutrient intake. For example, moving from a hay-based diet to a high-grain diet can lead to decreased water intake, as grains often have lower moisture content. This can put the horse at risk for dehydration, particularly if they are not acclimatized to the new diet or if they are not provided with adequate access to fresh water.

Other options, such as a high grain diet and cold weather conditions, can also affect hydration, but they do not directly imply a sudden shift in water intake or immediate risk like dietary changes do. While consistent rest periods may help maintain a horse's overall condition, they do not impact hydration as directly as a change in diet would. Therefore, dietary changes stand out as a potent risk factor for dehydration in horses.