Changes in milk composition during lactation in the tammar wallaby (Macropus eugenii).

Milk samples were obtained at regular intervals throughout lactation from tammar wallabies (M. eugenii). Total solids represented only 12% (w/w) of the milk at the commencement of lactation and gradually increased to about 40% at 36 weeks. Milk proteins represented 4% (w/w) of whole milk during the first 18 weeks of lactation, followed by a rapid increase to around 13% (w/w) at 36 weeks. Sodium and potassium concentrations were high in early samples of milk but declined to minimal values at 30 weeks. The milk was isosmotic to the plasma at all stages.