Breast-milk production and energy exchange in human lactation

Abstract

I . The milk production of one mother was determined post-partum for a period of 13 weeks, during which time breast milk was her infant's only source of food energy. The weight changes of both the mother and the male infant were recorded during this period.2. The food intake and activity pattern of the mother were also recorded for 4-week periods: at 2, 6, 10 weeks after birth and 2 weeks after the cessation of lactation, which was maintained for a period of 27 weeks.3. The infant regained his birth weight of 3310 g on the 14th day of life. His weight gain for the duration of the study, which averaged 233 g/week, was considered satisfactory.4. The daily milk production increased gradually from an average of 241 g during the 1st week post-partum to 995 g during the 12th week. The infant's maximum milk intake and hence food energy intake per kg body-weight was (range) 198-204 g milk and 55s-560 kJ/kg respectively during the 3rd to the 7th week, followed by a gradual decrease from the 8th to the 13th week after birth.5. The estimated efficiency of energy coversion for breast-milk production was consistent with other values reported in the literature.

The energetics of lactation in cooperatively breeding meerkatsSuricata suricatta

“…This compares with a cost per individual pup of 202 kJ d Ϫ1 calculated for a lactating mother. Therefore, an average of 10 helpers would potentially enable a typical breeding female to reduce her own DEE, whilst maintaining maximal MEI, and thereby support one extra pup (assuming a milk production efficiency of 85% (Commonwealth Agricultural Council 1980;English 1985)), resulting in a litter size of four; a 25% fitness bene-fit to the breeding female. It is important to bear in mind that these values were recorded for groups in the absence of allo-lactators.…”

“…However, during the study period, allolactating females decreased in mass, while the other categories of animals (dominant lactating females and nonlactating subordinate females) did not. This mass loss was equivalent to an energy deficit of 264 kJ d Ϫ1 , or 35 g milk d Ϫ1 (assuming an efficiency of milk production from body reserves of 0.85 (Commonwealth Agricultural Council 1980;English 1985)), which is potentially enough resources to support at least one extra pup per allolactator. Bearing in mind that babysitting and personal foraging are mutually exclusive activities (Clutton-Brock et al 1998), one possible explanation as to why allolactators lost weight during the week of peak lactation is that they may have babysat more than other categories of females did.…”