Okay..that is interesting. I have seen the same thing as well.
I wonder if the corn heats up their metabolism...they,ll eat it in the winter, but not very much in the spring, and almost not at all in summer.
Chickens love sweet corn. Open a can of corn and watch them go nuts eating it all up.
Cooked or uncooked, they love corn on the cob.
...no it does not need to be cracked, as long as they have access to some form of grit.
Happy happy happy girls....