If you don't already have it, I really recommend the Haynes Chicken Manual. It is a fantastic book for novices (and not so novices) covering all kinds of information from husbandry to how to make a coop to descriptions of various breeds.
While theoretically it is possible for chickens to live on wheat and corn, it would be similar to us trying to live on roast beef and bread. It would keep us from being hungry, but not very nutritionally balanced.
A commercial pellet, while it may not look appetising, does provide a balanced diet. Wheat and corn fed chickens also tend to put on weight very easily, especially around the breast and abdomen. And one thing you wil learn is that fat hens don't lay well - to the point where it can exacerbate problems like prolapses etc. Also, while chickens are good at slef selecting, they still may not get adequate calcium from the oystershell (especially if it is mixed with grit), and you may start to see an increase in soft or thin shelled eggs (which can become complicated if they break inside the oviduct or cloaca).
Some hens never become hand tame, though if you have the time to spend with them, just sitting in their area with a book, most hens are inquisitive enough to come and visit - especially if you sprinkle a few grains around our feet. it is handy if you can hand tame them, as it makes health checks much less stressful for everyone. You can check a bird over, gauge their weight etc.
If you are feeding lettuce and greens, please ensure that these are either directly from your garden, or if they are shop bought, they do not enter your kitchen prior to being chicken food (DEFRA rules).
I wish you many hours of chickeny happiness... and lots of fresh eggs
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