Eucalyptus Digestibility and Digestible Energy Requirements of Adult Male Koalas, Phuscolarctos cinereus (Marsupialia)*
D. E. UllreyA, P. T. RobinsonB and P. A. WhetterA
ADepartment of Animal Science, Michigan State University, East Lansing, Michigan 48824, U.S.A.
BJennings Center for Zoological Medicine, Zoological Society of San Diego, San Diego, California 921 12, U.S.A.
Three adult male koalas were individually fed a diet of Eucalyptus melliodora, E. robusta and E. sideroxylon plus trace mineral salt and water ad libitum. Fresh browse was offered daily for 14 days before and 7 days during quantitative collection of faeces. Samples of browse representing plant parts consumed were collected, and acid lignin ratio techniques were used to estimate nutrient digestibility. Estimates of apparent digestibility were as follows: dry matter, 54-70%; gross energy, 47-64%; crude protein, 32-50%; ether extract, 37-50%; neutral detergent fibre, 23-57%; acid detergent fibre, 9-55%; remaining proximate fraction [(dry matter)- (crude protein + ether extract + neutral detergent fibre + ash)], 78-85%. Total faecal acid lignin excretion was used to estimate digestible energy (DE) intake. Since body weights (W) were maintained during the study, DE requirements for adult maintenance were estimated to range from 257 to 411 kJ per kg W0.75 per day. If one assumes an 87% recovery in the faeces of dietary acid lignin, estimated DE requirements for adult maintenance range from 312 to 439 kJ per kg W0.75 per day. These values are lower than commonly accepted interspecific values for eutherians but are consistent with evidence that the koala has a relatively low basal metabolic rate.