I would not give them scratch before 6 weeks of age as it has been known to impact chicks' crops. Even after 6 weeks, I would only give it sparingly, if at all. Keep in mind that chicken scratch is not really chicken feed. Scratch consists primarily of cracked corn and several other grains, and while it is a source of energy, it is not a good source of vitamins, minerals, or protein. In cold, winter weather, chickens expend extra energy to keep warm and a little scratch just before the sun goes down can provide a little extra energy, but too much can cause obesity and obesity-related deaths.