Chicken and chicken by-product meal is 100% natural and it is 100% natural for chickens to eat meat, even chicken and chicken by-products.
In my opinion and others, any chicken feed that does not contain a animal protein of some sort should never be called "Natural"...
A lot depends on what you are already feeding..
If your feeding the average backyard chicken a good high quality feed that contains animal proteins and is around 20% proteins theres not much you have to worry about. If your feeding them say a lower end feed that is vegetarian based with no...