Developmental Changes in Composition of Rat Milk: Trace Elements, Minerals, Protein, Carbohydrate and Fat

Abstract

The concentrations of iron, copper, zinc, manganese, calcium and magnesium, as well as protein, carbohydrate and fat, were analyzed in rat milk during the course of lactation in rats fed a purified diet. As serial milking has been demonstrated to affect milk composition (1), lactating rats were milked only once at various times from days 0 to 28 after parturition. Concentration of iron decreased rapidly from 9 to 5 micrograms/ml during the 1st week of lactation and changed little thereafter. Similarly, copper concentration decreased considerably in early lactation, from 9 to 2 micrograms/ml, but then remained constant. Zinc concentration did not decrease during the 1st week of lactation, but dropped from 14 micrograms/ml in the 2nd week of lactation to 8-10 micrograms/ml in mature milk. Manganese was unique as its concentration decreased during the early days of lactation, from 0.3 to 0.1 microgram/ml, with a subsequent rise in late lactation back to 0.3 microgram/ml. Calcium and magnesium concentrations increased somewhat in early lactation and decreased slightly in later lactation, but the changes were fairly small as compared to the trace elements. Developmental patterns for protein, carbohydrate and fat were not very pronounced, although protein and carbohydrate increased somewhat in early lactation and later decreased. These data demonstrate that the nutrient intake of the suckling changes markedly during the early neonatal period. These changes should be taken into account in evaluating data on the trace element composition of tissues of suckling rats.

Exposure to Dams' Low-Fat High-Carbohydrate Diet during Pregnancy and Lactation Establishes a Preference for Fat by Their Offspring

“…It appeared that the high level of plasma lipid concentration in suckling pups was due to the feeding of high fat milk. Keen et al and Del Prado et al reported that the F ratio in rat milk was 70-75% (33,34). We also reported in a previous paper that the F ratio in the stomach content of 8-d-old suckling pups was 74-76% and that no clear difference was observed in the ratio among the groups of pups nursed by dams fed the low fat diet, the control diet and the high fat diet (16).…”

Milk Collection in the Rat Using Capillary Tubes and Estimation of Milk Fat Content by Creamatocrit

“…The fundamental role of maternal milk in the establishment of offspring immune and intestinal health 3 , coupled with evidence that breastfed infants are less susceptible to disease 2 , highlights the importance of identifying the milk constituents associated with disease processes in early life and the molecular mechanisms involved in their actions. The developing rat is a popular model for investigating the effect of various nutritional, physiological, and chemical interventions on early-life development 4 . The analysis of rat milk may therefore provide novel insight into maternal and offspring health.…”

Pups of Dams Fed Low-Fat Diet during Pregnancy and Lactation Showed Strong Preference for High-Fat Diet to Achieve Optimal Growth

“…We also reported in the previous paper that no clear difference in energy ratios (PFC ratio) in the stomach content of 8-d-old suckling pups was observed among the pups nursed by dams fed the LFD, the CTD or the HFD. Keen et al reported that the F ratio in rat milk was about 70% and no clear change was observed in the PFC ratio in milk during the lactation period (27). Del Prado et al also observed that the F ratios of milk from rats fed a LFD (25 g/kg diet) and the HFD (200 g/kg diet) were about 74 and 76%, respectively (28).…”