What should I feed my backyard chickens every day?

[FunkyMonkey]

I recently started keeping a few hens and want to make sure I am not giving them the wrong food. There is so much conflicting advice online about grains, kitchen scraps, treats, and complete feed that I am not sure what should actually make up the main part of their diet. I would rather get the basics right from the beginning than correct nutritional problems later.

What would you recommend I feed my chickens on a daily basis, and how much room should I leave for treats or scraps?

[Trias]

For the main diet, I would rely on a complete poultry ration that is formulated for the birds’ age and stage of production rather than trying to mix everything myself.
The University of Minnesota Extension explains that chickens should receive a balanced prepared feed containing the necessary vitamins, minerals, and protein, with laying hens also needing adequate calcium and grit.
A helpful American overview on how to feed chicken also notes that fruits, vegetables, grains, and insects can be part of what chickens eat.
I would treat kitchen scraps and scratch grains as extras instead of letting them replace the nutritionally balanced feed.
Penn State Extension similarly recommends feeding a complete ration that matches the bird’s age and production stage. 
Its guidance also distinguishes between starter, grower, and layer diets, which seems especially useful if the flock contains birds of different ages.
Another point I would not overlook is permanent access to clean, fresh water, particularly during warm weather.
For additional U.S.-based information, the Penn State Extension guide to raising a small flock of laying chickens gives a useful overview of feeding and general flock management.