Originally Posted by Speed Racer
Smudger, the person who told you this apparently knows very little about hay.
Hay isn't just a 'filler' to keep horses happy. In fact, some horses get only hay and no grain, and are perfectly healthy.
I can vouch for this! I feed only bermuda/timothy mixed hay. No supplements, no grain, no extra crap. My horses are in perfect health and have been for the past 10 years.
I suppose I should add that what you feed a horse does depend on what their profession is. I just ride trails for pleasure, so what I do isn't "hard work". Horses that are worked a lot or are undergoing vigorous training/prepping may need more than just hay because they're burning more calories. But more often than not one will find that hay suffices just perfectly.