They're a mixture of grains used as a treat (wheat, corn and others)...the corn also helps with warmth in winter. They are good to keep your chickens turning over thier litter when given inside the coop. I used them to get the birds out of the coop when I want to clean it, to get them in the coop if we have to go out. When my hens see me with a container of scratch they will go anywhere I want them too:>)
I am told, that when breeding your hens to add alot of scratch and some catfood to thier diet.