LACTATION AND ENERGETICS OF GROWTH IN THE BRUSH-TAILED BETTONG, BETTONGIA-PENICILLATA (MARSUPIALIA, POTOROIDAE) IN CAPTIVITY

Milk samples were collected from 20 captive bettongs at various times during the 140 days of lactation to determine milk composition. Milk c onsumption rates of young were measured, using Na-22 turnover, up to t he time of their permanent emergence from the pouch and before solid f ood was consumed. Milk composition followed the general patterns of ch ange observed previously in other marsupials and included the characte ristic drop in carbohydrate concentrations associated with permanent e xit from the pouch. Milk consumption rates increased from about 1.0 mL day(-1) at 35 days to about 23 mL day(-1) at 90 days, just before per manent emergence from the pouch. Increases in milk consumption were pa ralleled by changes in the size of the mammary glands, which reached t heir maximum size at about 100-110 days. The efficiency with which you ng used milk to accumulate body tissue ranged from 0.39 to 0.51 g mL(- 1). Milk energy and protein were converted to body tissue with efficie ncies of 21.3-29 6% and 70.1-93 5% respectively.