Originally Posted by crimsonsky
i have never heard anything like this before - grain being 60-70% of a young horse's diet? That just seems... off to me.
It sounded weird to me too when I learned about it in my Equine Nutrition class. But because the microbes in the horses cecum aren't fully functioning they can't digest hays and other roughage like adult horses can. So because of that they have more of a simple stomach digestive system like we do.
Because of it they get most of their energy from grain which they can digest easily instead of forage which they still can only partly utilize. This is also why you don't have to worry so much about colic and laminitis because that's caused by disruptions in normal hindgut fermentation patterns.
Of course as the young horse gets more microbes in the cecum it can digest forage and hay better and will slowly switch from a mostly grain diet to a mostly roughage diet.
Hope that clears things up! I know it sounds weird