Again a lot of this is down to personal preference, whether to feed a layers mash or pellets depends on how you want to feed your hens and possibly what they have been used to before.
It is worth noting, however, that the feeding of kitchen scraps (cooked and raw) is risky; it has been shown that the risk of the chickens catching salmonella is greatly increased, this is when the eggs can become contaminated and in turn become a risk to human health.
It is generally safer to feed a good quality layers feed along with some fresh greens such as cabbage or non-toxic plants from the garden. Chickens also require non-digestible grit to aid in breaking up food.
The digestive system of birds such as chickens is really quite different to that of mammals.
The food is taken in and enters the crop and is stored here while it softens a little and swells up. Food passes via the proventriculus and into the gizzard – this is equivalent to a stomach with teeth as the grit the birds eat is used to aid in grinding up food in the gizzard while it is broken down by chemicals from the proventriculus.
Food continues through the intestines and is absorbed, with some fermentation in the caecum. Droppings that are passed should be firm and brown with some whitish material on the top.