1. The intake of mammary secretion from delivery to day 5 post-partum was determined by test-weighing nine infants using an integrating electronic balance. The mean yield of colostrum for the first 24 h after birth was 37.1 (range 7.0-122.5) g and was 408 (range 98.3-775) and 705.4 (range 452.5-876) g/24 h on days 3 and 5 post-partum respectively.2. The milk yield of mothers on either day 14 or 28 post-partum was determined by test-weighing the mother. The mean milk yield was 1.156 (SD 0.167) kg/24 h. 3. A significant correlation (P < 0.001 ; r 0.85, n 42) was found between milk yield measured by test-weighing the infant and milk yield measured by test-weighing the mother, confirming that it is possible to obtain a similar estimate of milk consumed using either of the two methods of test-weighing.4. There was a significant positive correlation (P < 0.001) between lactose concentration and milk yield for the first 5 d post-partum (r 0.76, n 22); a significant negative correlation (P < 0,001) between protein concentration and milk yield (r -0.74, n 22) and no significant correlation between fat concentration and milk yield for the period studied.5. The calculated energy intake of infants during the first 24 h after birth was only 0.12 (range 0.02-0.29) mJ. This increased to 1.44 (range 0.83-2.18) and 2.99 (range 2.49406) mJ/24 h by days 3 and 14-28 post-partum respectively.

1. The milk yield of eight mothers each breast-feeding twins was determined by test weighing the mothers. Milk yield was determined at 2, 3, 6, 9, and 12 months post partum; however, only one mother was studied at all these times.2. At 6 months post partum the milk yield for individual breasts of three mothers fully breast-feeding and four mothers partially breast-feeding their infants ranged from 0.84 to 2.16 kg/24 h and 0.42 to 1.39 kg/24 h respectively. The average frequency of breast-feeding for the mothers studied at 6 months post partum was 15.4 feeds124 h.3. The milk yield of one mother fully breast-feeding 2.5-month-old triplets was 3.08 kg/24 h and the infants were fed twenty-seven times in 24 h.4. The concentration of lactose, protein and mixed fat in the milk from individual breasts of mothers fully breast-feeding their infants ranged from 65.6 to 82.2, 7.8 to 15.7 and 16.7 to 46.2 g/1 respectively. For the three mothers partially breast-feeding 12-month-old infants the values ranged from 54.8 to 71.8, 14.2 to 19.9 and 4.7 to 40.5 g/l respectively.5. At 6 and 12 months of age, the proportion of the total energy intake of the infants which was derived from breast milk ranged from 64 to 100% and 6 to 13% respectively.6. It is concluded that the maximum potential milk yield for women may be higher than the often quoted value of 70–800 m1/24 h.

Summary.Daily changes in the composition of the milk of two lactaling women were recorded from Ihe time of the last menstrua! period prior to conception throughout the first two months of gestation. The changes in the composilion of the milk from these women were compared to [he diiily changes in the milk composilion of [wo women during the peiiod of gradual weaning.In lhc weaning subjects the conccn[ralion of sodium and [o[al pro[cin had increased 14-and 1 6-fold, respectively, by the end of the study. The concentrations of potassium, glucose and lactose decreased 13-, 149-and 3 6-fold. respectively, from before weaning commenced lo the end of the study. These changes were closely correlated to the decrease in the suckling frequency of the infant. The concentration of sodium and total proiein in the milk from the unsuckled breast of two women was 11-and 2-8-fold higher than in [he milk from [he normally suckled breast of the same woman. The concentrations of potassium, glucose and lactose were 11-, 70-and 1-9-fold lower, emphasizing the necessity of a regular suckling pattern on the maintenance of lactation.The concentrations of sodium and total protein similarly increased during pregnancy, being 8-and 3-8-fold higher by the second month of gestation. The concentrations of potassium, glucose and lactose decreased 1-4-, 73-and 4 4-fold, respectively, over the same period of time. The changes in the milk composition showed no significant correlation to the infant's suckling frequency.The results indicate a progressive loss of secretory activity hy the mammary gland during weaning and early gestation. During weaning this loss appears [o be directly related to the decrease in the infant's suckling frequency, whereas during early gestation Ihere would appear to be an inhibition of milk secretion which over-rides [he positive stimulus provided by the infant's suckling. The mechanisms regulating the secre[ion of milk during weaning and pregnancy are discussed in the light of the compositional changes observed.

No abstract

Beginning with a historical account of advice to breastfeeding mothers, the authors review recent changes in the incidence of breastfeeding in Perth, and studies of milk production, constituents of various milks, management of breastfeeding and weaning, and circadian and menstrual cycle variation in breastmilk. The effects of contaminants, the seasons, and pregnancy are also discussed. (Birth Fam J8:4, Winter 1981)