There are many feed types that offer a 'complete' ration which includes all available nutrients and feed requirements. The problem comes with getting fresh feed. A lot of the time when you are feeding a 'complete' ration, you have to deal with how fresh the feed is. Typically you want to use the feed within 60-90 days of it being manufactured or packaged. With most places in the US, by the time that bag of feed actually gets on the shelf (not to mention to you) it is well past that 60-90 days mark and is no longer considered 'complete' because most of those nutrients have leached out of the formula. Your best bet is to try and find a type of food that your flock will readily eat and continue to supplement, either with the nutrients you are still giving them or by incorporating a 'fresh' element into their diet by letting them out to roam and collect fresh greens and bugs.