That is Bromus tectorum.
We refer to it as Bronco Grass here and just hate the seed heads. They get in your socks, penetrate the seams in your shoes and jeans and generally make life highly unpleasant walking through fields where the stuff has matured. Only thing worse is Foxtail.
I've heard it called Downy Brome or Cheatgrass as well.
I root it out where ever I can, cut the seed tops off elsewhere till permanent removal can be scheduled and make sure it goes to the landfill. The area immediately gets fertilzed and seeded with Pasture grass mix and kept damp till the replacement grass takes hold as this stuff likes poor soil and dry areas on the property.
It should never be found in any grass mixture as it is an invasive weed, probably imported from Eurasia.