The type of chicken feed you give to your hens will depend on size - a normal sized hen will need about 110g to 170g of grain a day & bantams will need about 50 to 85g a day. However if your hen is really free range and is allowed to wander free around your garden supplementing its diet with juicy grubs, insects and vegetation, 100g or less will suffice.
You can also supplement their diet with left over food – they have a hankering for carbs such as rice, pasta, bread and potatoes. They will also eat vegetables, fruit, seeds, hard cheese, meat etc. However avoid salty food, banana skins, uncooked potato peelings, chocolate and fish bones in your chicken feed. Like children they can be faddy eaters though – so try experimenting with different leftovers.
Grain & Corn
Chickens need a good balanced "Layers Mash" or "Layers Pellet" which contains all the grains, vitamins, minerals and proteins a hen needs to maintain good health and performance and can be acquired from any animal feed store or online. Pellets are easy for chickens to eat, however they may get bored if they are in a confined area; whereas mash keeps them happy for hours. As a treat you may like to give your chickens some mixed corn which is best scattered around on the ground. This encourages them to scratch around and take in grit which they need for digestion (see chicken digestion). Only use corn as a treat as they need to eat their mash or pellets to produce the maximum amount of eggs.
Grit & Oyster Shell
Chickens do not have teeth so they must have access to grit which the hen stores in the gizzard and uses to aid digestion (see chicken digestion).
Fresh clean water is essential for your chickens and should ALWAYS be available. It is important to regularly check the water supply, particularly in hot weather to ensure it's not run dry, as well as freezing conditions to ensure the water isn't frozen.