No it still goes to seed, lots of it. Then in Sept we have Gold Finches by the thousands.
Noxious weeds are the biggest threat to range land. Thistles are bad but not as bad as Spotted Knappweed. Knappweed has a natural herbicide in it's root system that kills other vegetation. And I have not seen cattle eat knappweed.
I have no problems with the thistle in the open areas or cropland that can be mechanically sprayed. My 1200 plus acres of pastureland consists of about 1/3 woodland, low wet areas, ponds and old farm sites with footings, holes old fences etc. I have spent a good bit of time hand spraying, and still do. I've lost the battle.
Oh I'm not the only one, thistles are everywhere and every pasture has them.
We did not have a thistle problem here until the dry years started. Most of the producers both dairy and beef brought in hay from North Dakota. This brought in the thistle and knappweed. That and the seeding along new highway construction. The seed used by county and state highway departments was infested with noxious weeds.
Be careful where you buy hay.