There are a number of reliable publications that state that treats (including grains and starches) should not account for more than 10 % of a chickens total diet (even worse, most breads do not even qualify as whole grains, but are refined). These 10 % recommendations include articles at http://www.backyardpoultrymag.com/scratch-grains-the-ultimate-winter-chicken-treat/, https://www.backyardchickens.com/a/feeding-chickens-an-introductory-guide, and http://www.rentacoop.com/Chicken-Treats.html. It's up to you of course, whether or not you accept this advice. Either way, I wish you good luck with your flock.What do you base your answer on?