Corn is very high in carbohydrates but does not provide protein, aminoacids, vitamins and other essential nutrients a healthy diet should include.
So feeding corn will lead to malnourished and poorly laying chickens with a fat pad on their lower abdomen and excessice fat accumulated around their inner organs. Fatty liver disease/sudden death caused by a ruptured liver is often seen.
Only in very cold temperatures do chickens need some extra carbohydrates in the evening to keep them warm at night.
Some poultry feeds contain lots of corn as corn is the cheapest ingredient, so always check the list of ingredients carefully.