Nitrogen and Urea Metabolism and Nitrogen Requirements of the Common Ringtail Possum, Pseudocheirus Peregrinus, Fed Eucalyptus Andrewsii Foliage.

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Abstract
The maintenance N requirement of mature common ringtail possums, P. peregrinus, feeding on a sole diet of E. andrewsii foliage, was estimated to be 380 mg .cntdot. kg-0.75 .cntdot. day-1 on a dietary basis, and 290 mg .cntdot. kg-0.75 .cntdot. day-1 on a truly digestible basis. The difference between these 2 estimates was due to a low true digestibility of N of 79%. Apparent digestibility of N was 58%. The level of urea metabolism in the ringtail was low compared with other herbivores. Only 40 mg urea-N kg-0.75 was recycled to the gut each day, but this was 96% of irreversible loss rate (i.e., endogenous synthesis rate) and 11% of the ringtail''s intake of truly digestible N. A low maintenance requirement for N, together with the recycling of a high proportion of endogenous urea to the gut, helps explain the ability of the ringtail possum to remain in positive N balance on a sole diet of E. andrewsii foliage of only 1.1% N content.