I have a horse back home, and even though they are such huge animals, their guts are extremely sensitive.
Horse hay is more meticulously grown than cattle hay (their four chambered tummy can digest anything. Those dudes are walking garbage disposals)
Horses on the other hand are soooooo picky.
I have know of horse people that show horses having to giant orange jugs of water from home because horses do not like anything that taste "funny".
If your buying from horse people, they will totally understand being choosy about hay.
When buying baled hay, the biggest concern is mold.
When hay is cut it has to stay in the fields until it is dried out.
If it is baled with too much moisture it will mold and rot.
Sometimes you can't tell this from the outside that nasty is brewing within the bale.
If hay is not baled too tight, you can put your hand between the flakes and see if is warm.
Warm / moist = BAD
If they bale using twine, look to see if it is rusted.
Rust = BAD
Everything else you already know
- fresh smelling
- weed free
- green hay is nice, but hay left in sun will bleach yellow.
It's still good it's just not as pretty. I've had my horse turn up his nose at green hay for his higher quality yellow hay.
Anyway,
Happy hunting.