To keep your horse healthy, most experts recommend ensuring your horse consumes 1.5 to 2.5 percent of its body weight each day in the form of forage. In short, forage should be the basis of all horse feeding programs and should serve as the primary source for all of the basic nutrients that your horse needs.
Of course, if you have a great pasture and if your horse is allowed to spend as much time on it as it wants, it is possible for it to eat more than it needs to stay healthy. In addition, not only can pasture intake be difficult to limit, but it can also be difficult to monitor unless you are going to watch your horse and record its eating habits for the entirety of the time that it spends at pasture.
For this reason, you will need to do some estimations to ensure your horse is obtaining the right amount of forage. A 1000-pound horse, for example, should consume about 200 pounds of forage. If your horse spends eight hours in the pasture, you can assume it will consume approximately one-third of its daily intake during this time. Therefore, the remaining two-thirds of its required daily intake will need to be obtained in the stall, perhaps in the form of hay.
Ideally, you should make up for this loss of forage as much as possible with hay and grain should only be added to help meet your horse’s energy needs. It is important to note that the amount of hay and grain that you need to feed will be affected by the quality of your pasture. As such, since your pasture quality will be affected by weather conditions, you may need to make seasonal adjustments to the amount that you feed.