Lactation and Energetics of Growth in the Brush-Tailed Bettong, Bettongia-Penicillata (Marsupialia, Potoroidae) in Captivity

Abstract

Milk samples were collected from 20 captive bettongs at various times during the 140 days of lactation to determine milk composition. Milk consumption rates of young were measured, using Na-22 turnover, up to the time of their permanent emergence from the pouch and before solid food was consumed. Milk composition followed the general patterns of change observed previously in other marsupials and included the characteristic drop in carbohydrate concentrations associated with permanent exit 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 permanent emergence from the pouch. Increases in milk consumption were paralleled by changes in the size of the mammary glands, which reached their maximum size at about 100-110 days. The efficiency with which young 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 efficiencies of 21.3-29 6% and 70.1-93 5% respectively.