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Digestion and Nitrogen Metabolism in the Koala, Phascolarctos cinereus 

C. J. F. HarropA and Robert DegabrieleAB

A School of Zoology, University of New South Wales, P.O. Box 1, Kensington, N.S.W. 2033.

BPresent address: School of Applied Sciences, Riverina College of Advanced Education, P.O. Box 588, Wagga Wagga, N.S.W. 2650.

ABSTRACT

The dimensions of different regions of the digestive tract and digestive efficiency were determined in koalas maintained on leaves from the grey gum, Eucalyptus punctata, in summer and winter trials. Intakes of wet and dry matter, and apparent digestibility of dry matter, compared favourably with values reported for various other herbivorous mammals. Seasonal differences were marginal. A low but positive nitrogen balance was generally maintained in both seasons, although the apparent digestibility of nitrogen was lower in winter. This was reflected in the values for dietary and apparent digestible nitrogen intakes required for the maintenance of similar levels of nitrogen equilibrium in summer and winter. Mean nitrogen balances in summer and winter were not signi- ficantly different at 0.040 and 0.034 g/kg W0,75 per day respectively. Daily dietary nitrogen intakes were significantly different, however, at 0,426 and 0,493 g/kg W0,75 in summer and winter respectively, while the apparent digestible nitrogen intakes were not significantly different at 0.180 and 0.127 g/kg W0.75 per day respectively. This is discussed in relation to the quality of the food offered. It is concluded that the digestive tract of the koala, presumably aided by the relatively large caecum, is well suited to the fibrous dietary matter on which the animal feeds.