Fiber Digestion in the Emu, Dromaius novaehollandiae, a Large Bird with a Simple Gut and High Rates of Passage

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Abstract
The ability to digest plant fiber was examined in the emu, a large ratite bird which is widely distributed in Australia. Emus digested between 35% and 45 % of the neutral detergent fiber (NDF) in their diets (NDF content 26%-36%). Hemicellulose was more digestible than either cellulose or lignin. The digestion and metabolism of cellulose and significant volatile fatty acid production showed that fermentative digestion was involved in NDF digestion. Energy from the digestion of NDF contributed up to 63% of the standard metabolism and 50% of maintenance requirements for energy on the highest fiber diet. The considerable NDF digestion was achieved despite the facts that the rate of passage of feed residues through the tract is rapid and the gastrointestinal tract is simple in structure; the distal small intestine (ileum) was the principal site of fermentation. The mean retention time of the fluid phase of the diet was 4.1 ± 0.2 h and that of the particulate phase was 5.5 ± 0.4 h (n = 11). The ability of the emu to digest and metabolize plant fiber may assist its survival during periods of decreased food quality and abundance in the interior of Australia.