Lionhead rabbits thrive on a diet primarily made up of hay or freeze-dried grass and fresh vegetables, with pet-food pellets making up less than half of an adult rabbit's diet. Young rabbits can be given a slightly larger amount of pellets, as they need the calories to grow. The amount should be tapered off as they age to prevent obesity.
It may seem counter intuitive that a Lionhead rabbit's diet should primarily be made up of nutrient-poor hay and grass. However, a very crucial part of any pet rabbit's diet is fiber. Giving a rabbit unlimited access to hay and grass gives it the roughage it needs to digest its vegetables and pellets. Fibrous material also forces a rabbit to use all its teeth, which promotes dental health.
Pellets should be fresh, and their purpose is to fill any nutritional gaps not covered by the vegetables given to the rabbit. A quality pellet should have at least 18 percent fiber and not contain any fruit or seeds, as these have unnecessary sugar. Rabbits don't need a large amount of sugar to be lively and energetic; a diet high in sugar promotes obesity and digestive problems such as cecal dysbiosis.
Domestic rabbits have delicate digestive systems, so while vegetables are an important component of their diet, any new vegetable should be introduced gradually to prevent upsetting their stomachs. Diarrhea resulting from sudden changes in the animal's food can kill it.