This is a two part question. A. Is it a good idea to feed your horse in the trailer? B. When traveling, how often should you stop to water and exercise your horse?
Whether to feed your horse in the trailer depends on the distance and length of time your horse is in the trailer. If the journey is scheduled to take six hours or longer, it is recommended to provide hay in the trailer. It is never recommended to provide the grain portion of the diet in the trailer. For trips less than six hours, it is generally recommended not to feed your horses in the trailer.
Unfortunately, many people are willing to provide horses with hay while traveling, but forget to provide adequate water. Research conducted by Kentucky Equine Research has shown that eating forage stimulates the thirst response in horses. Providing hay without adequate water gives horses a perfect chance to become dehydrated and potentially suffer from colic. Providing hay to nervous horses may provide a calming effect, but at the risk of the horse bolting (gulping) the feed and choking. If forage is to be provided while horses are in the trailer, it should be free of dust. Most hay nets are hung in what is known as the “breathing zone” around the horse’s muzzle. Dust blowing off the hay will be deposited directly into the lungs.
Therefore, it is recommended to soak the hay prior to placing it in a hay net. Providing hay cubes that have been soaked in water prior to feeding is an alternative to hay. Horses that are fed during transport need to be watered at least every four hours. If temperature and humidity are high, it is recommended that horses be provided with water at least every two hours. It may be helpful to carry water from home for horses that may be reluctant to drink from a strange water source. Ideally, horses should not be hauled for more than 12 hours at one time. If horses must be hauled between 6 and 12 hours per day, short periods of rest when the horses are actually unloaded from the trailer will not provide rest. It is best to stop and provide water, then continue on the trip without unloading the horses.