Around here everyone feeds grass
hay to
beef, horses, goats, sheep. Some farmers grass hay is top notch because they fertilize and care for their ground. Other people just grow grass year after year and it has little nutritional value because the ground is depleted and it may or may not be cut at the right time.
I would not only want to know the species of grass but the composition of the organic matter ( dirt) I’m going to grow it in. I would do a soil test and amend accordingly if I wanted mY critters to flourish. It’s really an ongoing
project year to year.
You might still have to add grains or...? But good grass can be good forage.