Convection requirement is established by total metabolic rate in the newborn tammar wallaby

Ventilation (VE) and metabolic rate, determined from both pulmonary and cutaneous gas exchange, were measured in 39 newborn tammar wallabies, Macropus eugenii, aged between 0 and 3 days. In 1-day-old animals both total metabolic rate (skin+lung exchange) and ventilation were approximately 50% of the values predicted for eutherian newborns of equivalent body mass. Hence, the convection requirement (VE/total metabolic rate) of the newborn tammar is close to predicted values for newborns and adult mammals in general. Metabolic rate in the newborn tammar is supported to some extent by cutaneous gas exchange, approximately 30% of the total in the 1-day-old animal. This ratio diminishes with increasing age as the lung takes on an increasingly more important role for respiratory exchange. The early establishment of the convection requirement in the newborn tammar, despite significant cutaneous gas exchange, provides supporting evidence that metabolic rate per se is important in establishing the level of ventilation.