Cows occur in most grassland or wooded biomes, cows will drop raw beef and/or leather when killed. If killed by flame or fire; cooked beef will be dropped.
Cows can be breed with the use of wheat (right-click) two or more cows in order breed a baby cow. This is especially helpful when building a fenced in herd of cows.
Chickens occur randomly in most biomes within Minecraft, chickens when killed will drop raw chicken and/or feathers. If a chicken is killed by flame, it will drop cooked chicken.
Chickens drop Eggs at random while active in Minecraft, eggs is an ingredient to make a Cake. Eggs can also be thrown (right-click) but do no damage to any mob or player that may be hit by them. There is 5-15% chance that when an egg breaks on the ground; a baby chicken may hatch.