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Meeting the energy requirements for lactation in a macropodid marsupial: current nutrition versus stored body reserves
Author(s) -
Cork S. J.
Publication year - 1991
Publication title -
journal of zoology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.915
H-Index - 96
eISSN - 1469-7998
pISSN - 0952-8369
DOI - 10.1111/j.1469-7998.1991.tb04325.x
Subject(s) - lactation , biology , macropus , zoology , offspring , marsupial , gestation , ruminant , tammar wallaby , pregnancy , ecology , pasture , genetics
Food intake and digestion were investigated at four stages in the first 218 days of lactation in tammar wallabies ( Macropus eugenii ) carrying litters of one, and in non‐lactating females as a control. This period of lactation in tammars, which includes the phase of exponential growth of the young, is comparable to gestation plus early lactation in ruminant placentals. Food and energy intakes by mothers remained at the non‐lactating level while rate of growth of young was slow (up to Day 105 of lactation) but then rose as the growth rate of young increased, keeping pace with the predicted requirements for milk synthesis and export. There was no indication of the energy deficit seen in late gestation and early lactation in many herbivorous placental mammals. The gross efficiency of utilization of ME for growth of offspring was estimated as 13–15%, which is at least as high as values for placentals during gestation. The mean intake of metabolizable energy (ME) at 218 days was 603 kJ.kg ‐0.75 .d ‐1 , which represented 136% of ME intake by nonlactating females, or an increment of 159 kJ.kg ‐0.75 .d ‐1 . It was estimated that ME intake may rise to 773 kJ.kg ‐0.75 .d ‐1 at peak lactation, which would be 174% of the non‐lactating level or an increment of 329 kJ.kg ‐0.75 . d ‐1 . This allometrically‐scaled increment is similar to values for some ruminants that use body reserves extensively to offset peak lactational food requirements. These and previously‐reported trends suggest that ecologically comparable herbivorous marsupials and placentals utilize different physiological strategies to minimize demands on food resources during reproduction, but that both daily and overall demands can be similar.