I also use Equi-analytical. Equi-analytical Laboratories - Profiling Feed for Better Nutrition
But you have to have a corer and drill into the hay for the test samples
It comes out of the bale looking like oregano, then you just put it into a clean zip-lock bag and send it off with a check for the particular test you want done.
They e-mail you the results as long as you remember to check that box on the form
What I have learned about paying Co-ops to do the testing, is they don't know diddly about testing hay for horses.
They do a bang-up job testing hay for cattle but we're not looking for the same things in cow hay as we are in horse hay