I just purchased a 50 lb. bag of Purina Start and Grow Sunfresh Medicated Crumbles for six day old chicks we are picking up in a couple of days. There is a statement on the white tag sewn onto the bottom of the bag under the Heading CAUTION, it reads- "Do not change the litter while giving this feed unless absolutely necessary." Do you have any idea why it suggests we should not change the litter unless absolutely necessary? Under the heading DIRECTIONS it reads "Feed continuously as the sole ration to chick and replacement pullets from hatch to onset of egg production (18-20 weeks)."