Because of their unique digestive systems, rabbits require a diet that's high in fiber, low in protein. The nucleus of any good rabbit diet consists of pellets, fresh hay, water, and fresh vegetables. Treats, such as fruits or prepared rabbit snacks, are acceptable but should be used very sparingly and in small quantities. It's important for your rabbit's health and longevity that you commit to feeding it a proper diet.
Pellets have long been considered the base of a rabbit's diet. But pellets are actually more important in the younger stages of rabbit development than in adult rabbits. That's because they are highly concentrated in nutrients, helping ensure proper weight gain in younger rabbits. A quality pelleted food should be high in fiber (16% minimum). Watch the label, and make sure it is not also high in protein because an improper protein/fiber ratio can lead to digestive problems. As a rabbit reaches maturity, however, pellets should make up less of the diet - replaced with higher quantities of hay and vegetables. Overfeeding pellets in mature rabbits can lead to obesity, as well as other medical conditions.
Young adult and mature adult rabbits should have fresh hay available 24 hours a day. Rabbits less than 6 months old may have alfalfa hay, but older rabbits should have grass hays such as timothy or oat hay. Hay is essential for providing the roughage rabbits need to keep their digestive systems on track. Just like cats, rabbits groom themselves and can develop hairballs. Unlike cats, however, they cannot cough them up. That's why fiber is so important in their diet. It helps pass the hair through before it can develop a blockage.
Fresh water should be available to your pet around the clock. Each day, change the water in the dish or water bottle with fresh water. On a weekly basis, sanitize the water dish/bottle with a mild dish detergent and rinse thoroughly before adding drinking water.
Your rabbit's diet should also be rich in vegetables. They not only provide valuable roughage, but also essential vitamins. This is especially important as you begin to decrease the portion of pelleted foods you feed your rabbit. The nutrition has to be made up with the other foods in your rabbit's diet. Vegetables can be offered as early as 12 weeks of age. Introduce new vegetables one at a time, and avoid those that cause soft stools or diarrhea. Continue to add new varieties, with the best ones being dark leafy vegetables and root vegetables. Try to serve up vegetables with different colors, including dark yellow and orange. Once your rabbit is quite used to several vegetables, feed it a mix of several kinds daily to ensure proper nutrition.
Rabbit teeth grow continuously throughout their lives, so the increase in vegetables and hay is also important to your rabbit's dental health. The high volume of chewing required for swallowing vegetables and hay ensures proper wear on the teeth. A diet that requires little chewing produces uneven tooth wear, causing spikes of enamel to grow on the outer and inner sides of the teeth. These spikes can cause severe oral pain and excessive salivation (often called "slobbers"). They also cause reluctance to chew, inability to close the mouth, and reduced food intake. The situation deteriorates as the teeth continue to grow, and, if it is not treated, results in severe malnutrition.
In addition to the dietary tooth wear vegetables provide, rabbits can be given chew treats to help wear their teeth down.
Treats, including fresh fruits, should be given sparingly because of their calorie content. Rabbits can digest small quantities of oats and barley, but again, they generally provide more calories than necessary. And, too much carbohydrate has been associated with enteritis in rabbits. Avoid feeding human snack foods altogether - absolutely no chips, chocolate, cakes, etc.