Browse representing 1.5 m of terminal growth from 11 species of Eucalyptus shoots or mature tree limbs was divided into portions which were either consumed or rejected by captive koalas. The following nutrient concentrations (dry basis) were found in preferred browse: crude protein, 5.9-17.8%; ether extract, 5.5-19.2%; neutral detergent fibre, 16.8-37.5%; ash, 3.2-5.6%; remaining proximate fraction [(dry matter) - (crude protein + ether extract + neutral detergent fibre + ash)], 31.7-64.8%; calcium, 0.28-1.95%; phosphorus, 0.08-0.42%; sodium, 0.03-1.29%; potassium, 0.30-2.06%; magnesium, 0.12-0.44%; iron, 67-274 ppm; copper, 2.1-15.8 ppm; zinc, 17-54 ppm; and selenium, 0.03-0.42 ppm. Preferred browse, as compared to rejected browse, had significantly higher concentrations of crude protein, remaining proximate fraction, phosphorus and potassium, and significantly lower concentrations of ether extract, neutral detergent fibre, acid detergent fibre, permanganate lignin, gross energy, calcium, iron and selenium.

Three adult male koalas were individually fed on a diet of Eucalyptus melliodora, E. robusta and E. sideroxylon plus trace mineral salt and water to appetite. 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. Apparent digestibility of DM was 54-70%, gross energy 47-64%, crude protein 32-50%, ether extract 37-50%, neutral detergent fibre 23-57% and acid detergent fibre 9-55%. Total faecal acid lignin excretion was used to estimate digestible energy (DE) intake. Since bodyweights (W) were maintained during the study, daily DE requirements for adult maintenance were estimated to range from 257 to 411 kJ/W0.75. If an 87% recovery in the faeces of dietary acid lignin was assumed, estimated DE requirements for adult maintenance ranged from 312 to 439 kJ/W0.75. 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.