Scratch is not a complete food; it has no added vitamins and mnerals, and the protein is low. The worst of it is they love the corn and will eat it in preference to more nutritious foods.
The quality of scraps varies a lot, as does the quality of forage. If your scraps are your own leftovers and the forage has lots of grass, green lants and bugs, they will probably eat these thigs rather than feed for the most part. If you can get an all prupose or All Flock type feed that costs less than layer, it should be fine,especially if they hve a little oyster shell -- which they probably won't eat much of. You could also fees starter, grower, etc., especially if you can change them aoround a little.
You could see whether there is a feed mill in your area that formulates their own feed; often this is much cheaper.
Decades ago, people fed cracked corn, forage and table scraps, and the chickens survived -- but they tended to be thin and not in the best of health.
