The feed of horses normally consists of a combination of raw feed and power feed. Oats, barley, and wheat contain more energy than grasses, and form a good alternative to feed horses.
Not only the ration but also the feeding strategy is important for feeding horses. When the amount of feed is adjusted to the daily energy need, this is called norm feeding. The horses nutritional requirements are met at any time during the day. On rest days it will get a little less and on working days a little more. The problem with norm feeding is that on days of intensive labour, the horse is not yet able to take in enough energy.
Theres also the so called flat feeding, which means that the horse will get the same amount of food each day. The energy requirements will then be determined over a longer period of time. The horse will eat a little less than required on working days, but this does not cause any problems, as the horse will eat a little more than required during rest days. At the end of the period, the horse has in total taken up as much energy as it needed.
In practice, a combination of both feeding strategies often works best. The individual need of the horse is the starting-point of course.