Energy expenditure and protein turnover in three species of wallabies (Marsupialia: Macropodidae).

Relationships between basal and fed metabolic rates and whole-body protein turnover rates were examined in three species of wallabies, the red-necked pademelon (Thylogale thetis), parma wallaby (Macropus parma) and tammar wallaby (M. eugenii). There were no significant differences among wallaby species in basal metabolic rate (BMR) which was 30% below eutherian mammals. However, the fed metabolic rate of the tammar was lower than that of the other two species (P less than 0.05), as was the protein turnover rate (P less than 0.01) which is consistent with its lower voluntary feed intake and with its lower maintenance nitrogen requirement. Protein turnover rates in the wallabies were 23-47% lower than in eutherian mammals. Similarly, protein synthesis made a lower contribution to fed metabolic rates in the wallabies (7-8%) than in eutherians (17-25%). Thus, compared with several eutherian species, macropodid marsupials have low rates of both energy and protein metabolism, but within the macropodids there is not necessarily a close link between basal metabolic rate and whole-body protein turnover.