In my animal grazing area, I have at least a dozen different grasses, plus the occasional weed. This gives the animals a good, balanced diet.
I just can't fathom why some folks insist on feeding animals a single kind of hay. First of all, animals in their natural environment do not seek out and eat grasses that have been cut then dried for several weeks. They eat fresh. Uppity livestock types call it "forage" and caution about the amount that is "safe."
Gimme a break.
Second of all, animals do not eat one kind of grass only. They move from place to place eating first one kind, then another, and around and around until it eventually ALL gets eaten. The ones that taste best, or have needed nutrient content, go first. In a mixed environment, the animals take in all of the grasses, and get a far more balanced nutrient-rich diet.
As hay sits, nutrients leech out anyway. So the dry, single-species hay fed to static animals is a feedlot seriously impacts their overall health. Giving them fresh, diverse pastures lets them eat a natural, God-designed diet that encourages optimum health.
Oh yeah - they need water, too.