Scratch is a treat and no more than 1-2 tablespoons a day should be given to the chickens. Chickens treats are more for us than for chickens, but they are an excellent way to bond with your flock and train them. I throw scratch and shout "Chick chick chickens!" once a day and the girls come running. I do this to get a head count, enjoy the silliness of running birds, and keep them trained to come when I call. You can also use this to lure them back into a run if they were free ranging. I also like to sit on the ground and feed the girls from my hand. Leafy greens and lettuces can be fed basically as much as you want. Other treats, watermelon, squash, apples, etc, can be fed a little more than scratch, but are still a bit sweet and carb heavy, so moderation is needed with those treats too. If chickens are kept in a run, scratch and other treats are a good way to encourage natural chicken behaviors as well.