Shouldn't but if it were many other animals I'd say remove the leaves. Oak is high in tannins which can cause health problems for mammals. As a generally rule don't purposely feed oak leaves to anything. I wouldn't worry about chickens finding them on their own though.
Acorns would be fine. The hulls still contain tannins but animals rarely eat that and it's not nearly as much as what's found in bark and leaves. My stock tanks turn brown and have to be emptied more frequently in the fall because of all the stuff falling off the oak tree and releasing tannins into the water.