Young adult rabbits, in the range from 7 months to 1 year of age, should be introduced to Timothy, grass hays, and oat hay. At this point, they will require little alfalfa hay, as well as fewer pellets. Alfalfa hay has more calories and calcium than rabbits need at this stage, and the high calorie content of pellets can cause weight problems. Pellets still offer a good nutritional bang for the buck, but instead of offering unlimited pellets, a good rule of thumb is to offer 1/2 cup per 5 lbs. of body weight daily. To make up for the nutrient loss, you must increase your rabbit's intake of vegetables and hay.
A variety of hay and straw must be encouraged all day long at this stage. Increase your rabbit's daily intake of vegetables, but introduce one vegetable at a time. If any vegetable seems to cause digestive problems, avoid feeding it in the future. You can feed your rabbit some fruits during this stage, but because of calories and less nutritional value, limit them to no more than 1-2 ounces per 6 lbs. of body weight daily.
Mature adult rabbits (older than 1 year) should be fed unlimited timothy, grass hay, oat hay, and straw. Once again, you should reduce the pellet portion of the diet. A standard guideline is 1/4 cup per 5 lbs. of body weight per day. Several servings of vegetables are required per day, as well. Make sure to choose dark, leafy greens. Iceberg or other light-colored varieties won't cut it. Also, make sure to offer dark yellow and orange vegetables. Treats, including fruits, must be fed sparingly.
Senior rabbits, over 6 years of age, can be fed the same diet as mature adults if their weight is being maintained sufficiently. You may need to increase pellet intake if your pet is unable to maintain his weight. Alfalfa can also be given to underweight rabbits, but only if calcium levels are normal (determined by a blood workup). If calcium levels are high, then alfalfa is not a good idea.
Because the front incisor teeth of rabbits grow continuously throughout their lives, they must have access to something safe to chew to keep their teeth worn down. If not accommodated, their teeth can overgrow and cause malocclusion (their teeth do not meet each other normally), seriously impairing their ability to eat and enjoy life.
Many rabbits can live ten years or longer. Making sure you have the knowledge of their dietary requirements (and a commitment to providing them) goes a long way to ensure your pet is healthy and happy during all your years together.