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Kitchen scrapes and other treats should only take up 10% of their daily diet. They need some sort of commercial feed besides it. Either feed them a layer feed, a grower feed or a flock raiser. This will insure that they get the proper nutrients they need. Kitchen scrapes are good to feed but are not the best in nutrition.
Greens, however, can be fed all the time any time. Grass also counts as greens. Amazingly, grass provides approximately one quarter of a chicken’s daily nutrient requirements resulting in them eating less feed and lowing your feed costs! Grass is high in protein, iron and vitamins E and C. However, there are some things to be carful of when allowing your flock to eat grass. Make sure it’s not treated with any chemicals or pesticides. Also, if you watch your chickens free range you will notice that they only eat the tops of the grass blade. So when harvesting grass for them, don’t give them big, long pieces as this can result in crop binding or impacted crop.
Also they need extra calcium once they start laying. Oyster shell or eggshells can be fed as the calcium.
Good luck with your flock!