I have always fed an all grain diet, as I like to know what my birds are eating and you don't know whats in pellets, besides which millions of chicken all over the world have never seen a pellet and they do alright.
The birds do very well on it, BUT need free range to make up the difference in protien. I have about 300 birds here including chicks and growers.
Chicks start off on chick crumbs and as soon as the can handle grain they go onto it. I use Wheat, cut maize and rolled Barley with Cider vinegar and cod liver oil.
If you only have a few birds it's easy to make up the shortfall on protien using ether vegitable or animal protien.
Just read the labels and see what there is in it., beware of salt content.
Dried milk powder is very good (animal) Spinach and other greens including peas and beans also can be used.
Fresh grass and greens contain a high protien.
You will see a drop in egg numbers, especially at this time of year, but your birds will be healthier for it.
More on feeding on my web page.