Changes in Milk Composition During Lactation in the Tammar Wallaby (Macropus Eugenii)

Abstract

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.

Evolution of Lactation: Ancient Origin and Extreme Adaptations of the Lactation System

“…Important changes occur during the lactation cycle of marsupials in terms of mammary gland development, milk production, milk composition, and development or behavior of the young (26). This is in sharp contrast to eutherian mammals with their larger investment in gestation (97) and milk of a relatively constant composition, apart from the initial colostrum during the immediate postpartum period (42).…”

“…Under certain conditions, some species, such as the tammar wallaby (Macropus eugenii), may produce milk of differing composition from adjacent mammary glands. This phenomenon, called asynchronous concurrent lactation (ACL) (51,71), demonstrates the importance of local control on the lactation program, including major shifts in the relative milk content of carbohydrates, lipids, and proteins, as well as the phase-specific expression of major milk proteins (26).…”

Cross-fostering of the tammar wallaby (Macropus eugenii) pouch young accelerates fore-stomach maturation

“…At the onset of Phase III of lactation, the young begins to exit the pouch and commences consumption of herbage while still consuming milk. This phase is characterised by a large increase in volume of milk secretion, but a sharp decrease in carbohydrate levels that are mostly monosaccharides (Messer and Green, 1979), while protein and lipid levels increase to become the major components in the milk (Green and Merchant, 1988;Green et al, 1980;Nicholas, 1988). Protein composition changes considerably with secretion of different proteins at specific phases of lactation (Green and Renfree, 1982;Sharp et al, 2009).…”

“…In contrast, marsupials, such as the tammar wallaby (Macropus eugenii) undergo a relatively short gestation, give birth to an altricial young and have a long lactation (Tyndale-Biscoe and Renfree, 1988). The major milk constituents change progressively during this period (Green and Merchant, 1988;Green et al, 1980;Green and Renfree, 1982;Nicholas, 1988;Renfree et al, 1981) to accommodate the changing nutritional needs required for the considerable growth and development of the altricial neonate. Lactation in the tammar wallaby has been well characterised and has three main phases (Nicholas et al, 1997;.…”

“…Phase I is the 26-27 days gestation followed by birth of the altricial neonate, also termed the pouch young (TyndaleBiscoe and Renfree, 1988). The subsequent 200 days (Phase II) is characterised by lactogenesis and the secretion of dilute milk enriched in complex carbohydrates and low concentrations of proteins and lipids (Green et al, 1983(Green et al, , 1980Green and Renfree, 1982;Messer and Green, 1979). At the onset of Phase III of lactation, the young begins to exit the pouch and commences consumption of herbage while still consuming milk.…”