Hay testing

So how do you know if the hay you are buying is really "good" horse hay?  Lots of people equate alfalfa with "good" hay, but alfalfa is really too high in protein to be fed to almost all horses.  Some horses that get a huge workout every day can deal with alfalfa.  Horses can receive all the nutrients needed to thrive from hay.  grain is needed only on rare occasion and oats is the preferred grain if used.  Quality of hay required depends on the growth stage of the horse, the amount of work the horse does and whether or not the horse is pregnant.  Purdue University has some very good information on hay quality and horse requirements.