Digestive Physiology and Nutrition of Ratites

The exploitation of African ostriches, Australian emus and South American rheas as producers of skins, meat and feathers, and the protection of cassowaries in Australia and New Guinea and kiwis in New Zealand from becoming extinct, emphasise the need of knowledge about nutritional requirements of ratites. Although the general anatomy of the digestive tract of ratites is comparable to that of other avian species, they are unique in that they all lack a crop, and some (ostrich, rhea, emu) have evolved some form of fibre fermentation. The cassowary is the largest obligate frugivorous bird, whereas the diet of the kiwi can be described as carnivorousyinsectivorous. Vigilance plays an important role in the feeding behaviour of the ostrich and rhea, while smell is used by the nocturnal kiwi to locate food. Information on the digestive processes and nutritive value of feed ingredients in ratites are limited, and knowledge about nutrient requirements is extrapolated from theoretical models developed with domesticated poultry species.