Off the top of my head, c orn has both digestible and indigestible components. It is not a complete source of protein for humans. Missing lysine.
The indigestible parts are composed of cellulose, cellulose like compounds and lignin.Fiber, which though indigestible promotes health .
Europeans called animal feed corn. Perhaps this is the source of the myth of indigestibility. Some corn is very hard and better for animal feed.
An enzyme may be added to corn silage so that even the indigestible parts becoming digestible.
revery:
In Oregon when the high sun sugared up the raw corn, we ate it greedily, like warm candy, from the stalk