Hay Gone to Seed and Horses

Had a horse customer that got some hay last year from someone, second cutting, with foxtail in it and after a vet bill, they bought hay from me.

Is foxtail seed the only seed that can damage a horse's mouth? We've got some mixed grass hay coming this year, probably everything in it from early maturing/seeding bluegrass, orchard grass, fescue, a lot of sweet vernal grass - pretty much anything a broadleaf herbicide won't kill.

All of the above have their own maturing dates and some will go to seed before cutting.

Aside from foxtail, are any of these other grass seeds harmful to a horse?

Hay Gone to Seed and Horses