Even though he's domesticated, your pet rabbit has nearly the same nutritional needs as a wild rabbit. The difference is that he can't just go nibble on different types of grasses and plants throughout the day like a wild rabbit, so he needs a little extra help from commercial food.
Grass and Hay
Ideally, grass is the main dish in every meal for both pet rabbits and those in the wild. Hay is grass that's been grown specifically for feeding animals, so when you feed your pet rabbit hay, you're actually giving him a type of grass. In the wild, rabbits must eat whatever grass is available to them. They also spend a lot of energy searching for food. Your pet rabbit doesn't have a choice and has to eat what you give him, so make sure it's a type of hay that won't make him too fat. Timothy, oat, bermuda, orchard grass or wheat hay are all good choices for pet bunnies. Alfalfa hay has too many calories and too much calcium for rabbits and should only be given as an occasional treat.
Obviously, wild rabbits aren't eating manufactured rabbit pellets. They get the nutrition they need by eating a variety of plants. Since pet rabbits don't get to eat several different types of plants each day, it's a good idea to feed them a small amount of pellets to make sure they get the vitamins and trace minerals they need to stay healthy. Avoid pellets that have grains, seeds or fruit since these are just for human appeal and not so good for your rabbit. Most pet rabbits need about one ounce of pellets per day for each pound of body weight in addition to plenty of fresh hay.
Rabbits don't live on carrots and lettuce alone. Vegetables are a good source of vitamins, and both wild and domestic rabbits like to eat vegetables. However, they shouldn't be the only thing they eat, nor even the biggest part of the diet, because vegetables don't have enough of the long fibers rabbits need. Long fibers are found in grass and hay and are vital to the digestion process because they keep things moving through a rabbit's body. Pet rabbits should get a small serving of vegetables each day such as carrots, bell peppers, radish tops, squash, eggplant and Brussels sprouts. Make sure the veggies have not been treated with pesticides.
Wild rabbits eat small amounts fruit as they find it, such as small berries. They usually eat other parts of the plant, as well, so they aren't just getting sugary fruit. Pet rabbits don't need fruit in their diet. Too much fruit can make your bunny fat or give him diarrhea. A small fruit treat now and then won't hurt, and you can give your rabbit a raspberry, blueberry, blackberry or strawberry on occasion, or a small piece of apple, melon, peach or pear.