We would recommend a good quality grass hay if it is available in your area. Orchardgrass or smooth bromegrass hay would work fine. You did not say how old your horse is, but if your horse is mature, a high quality orchardgrass, smooth bromegrass, or mixture of alfalfa with either of these two grasses would make excellent quality horse hay that is highly acceptable. Of course, it is important to have the hay tested for nutrient value before purchasing. The minimum the hay should be analyzed for is crude protein, crude fiber or neutral detergent fiber, moisture, calcium and phosphorus. An excellent quality grass hay such as orchardgrass should have a crude protein value greater than 12%, a crude fiber value less than 26%, neutral detergent fiber less than 60%, moisture content no higher than 15%, calcium around 0.25%, and phosphorus around 0.2 to 0.3%. These values, except for moisture, are on a 100% dry matter basis which most lab reports will give you as an AS FED value (as it comes from the bale) and a 100% dry matter basis.