It is important to choose a good quality hay for your horses. Forage makes up about 50 to 90 percent of a horse's diet, and much of this comes from hay, especially in the winter. The most important factor in determining hay quality is the stage of plant maturity at the time of harvest. Young immature plants contain more nutrients than older plants with more stems, and there are also some other factors to examine when selecting hay for your horse. The first thing is you would like to see a high leaf to stem ratio and this goes back to age of the plant at harvest as younger plants are more leafy. The plants with more leaves are more digestible, and you also want plants with smaller stems which also indicates the plants were younger when harvested. Good quality hay is also soft and pliable so if you take a handful and squeeze it, it should feel soft and not like a handful of sticks. And hay with no seedheads indicates the plants are young so if you see a hay sample with lots of seed heads, that hay is also likely to be stemmy and less digestible.
Another important factor is the smell of the hay. It may take some experience to determine a difference in smell, but hay that smells musty or moldy is not a good choice. Mold and musty smelling hay is less palatable for your horses and can even cause allergic respiratory symptoms to occur in some horses. There also should be very little dust. Hays that are poor quality may contain dirt, mold, weeds and other foreign materials. Lastly, good quality hay should be bright green in color with little fading of the leaves.