A horse generally consumes about 1 to 1.4 lb of forage/hr when out on pasture. So that is a guideline to use for how long you will need to keep him out. Body condition scoring can also be used as a guide to keep him at the ideal weight. You can supplement with hay and grain as needed to maintain body condition, making sure to feed a minimum of 1.5% of body weight per day in forage. A good guide for body condition scoring in horses can be found at this link: How to Body Condition Score Horses. Also, remember that the horse still needs a salt source and may need a supplement to balance vitamins and minerals. This is most important in young, growing horses.
