Not sure who told you that, but they heard and/or read incorrectly
The study done on the 5lb of concentrates was on high cereal grain meals, though I don’t remember if that was straight cereal grains, or a commercial feed high in cereal grains. Either way, it doesn’t matter. The issue is how much starch you’re pushing into the hind gut.
Even then, the actual answer is 0.5% of the horse’s weight as your max, so that 5lb is for a 1000lb horse, but it’s 6lb for a 1200lb horse, 7lb for a 1400lb horse, etc.
And, the lower the starch (which typically means it’s highly forage- and fiber-based), the more you can push the amount a bit. So, something like a non-cereal grain senior feed could be fed at 6lb for a 1000lb horse. I wouldn’t push more than that.
yes, hay pellets is a concentrated form of food, but “concentrates” is usually limited to a bagged commercial feed or cereal grains… But, like “grain”, “concentrates” really needs to be defined in context in order to make any statements or implications about what it’s doing
An actual nutritionist? Or a feed rep? What company? I wouldn’t be surprised if it was Tribute, many of these reps give the WORST advice No actual PhD or even MSc iwth experience nutritionist would say that about hay pellets
The difference is the scratch factor, not how the fiber is processed. Pellets and finely chopped hay doesn’t have the same scratch factor that regular hay does. That scratch factor is part of what helps keep manure moving along. It doesn’t mean you can’t have a healthy horse without any long stem forage, certainly all these old toothless horses prove that. It just takes more care to make sure things move along
Not all forage is digested, and it’s not supposed to be