Ratites are flightless birds and do not require the high-energy diets of flighted birds. Ostriches, rheas, and emus consume low-quality roughage in nature, which is fermented in their intestinal tract. The nutritional requirements of juveniles are much higher in protein and calcium than those of adults. Breeders have even higher calcium requirements ( see Table: Selected Nutritional Requirements for Ratite Production a Selected Nutritional Requirements for Ratite Production a ).
In most parts of the world, the commercial breeding market for ratites is declining; however, in some areas significant numbers of ostriches and nandus are being kept. Ratite production for meat and leather has necessitated the development of diets to maximize growth and minimize cost. Bringing an animal to market in minimal time is financially advantageous, but excessively rapid growth can lead to angular deformities of the legs.
Cassowaries are rainforest ratites and are primarily frugivorous. They are not raised commercially, and their nutritional requirements are not documented. Adult birds often consume 3–5 kg of food/day. Diets fed in zoos include fruits and vegetables such as bananas, apples, tomatoes, papaya, watermelon, grapes, mangoes, plums, nectarines, cherries, kiwi fruit, figs, sweet potatoes, and carrots. These are commonly supplemented with animal protein (eg, day-old chicks, mice, dry dog food).