Changes in composition of rat's milk in the stomach of the suckling

Abstract

1. A study was made of the partition of the major constituents of rat's milk during the formation of the clot in the infant rat's stomach.2. Milk was obtained from the dams by manual expression after separation from their litters for periods ranging from 12 to 23 h.3. The ratio of fat to protein in the clots removed from the stomachs of the 11-day-old pups was more than double that found in the milk. The difference was due to the high fat content of the clot.4. The stomach contents of DUDS which were allowed to suckle for I h following a 12 h separation from their dams had fat to protein ratio similar to that of the expressed milk, When suckling was prolonged, the ratio reverted to that of the established clot.5. Milk secreted under conditions of uninterrupted lactation and promptly recovered from the stomachs of pups previously fasted had a value for fat to protein comparable to that for the clot from a normally fed pup. An interruption in suckling therefore reduced the fat content of the milk.6. Part of the carbohydrate in rat's milk is secreted in a bound form. Lactose accounts for approximately one half of the total carbohydrate. Evidence is presented which suggests that the remainder may be an isomer of lactose.7. Fat and lactose undergo hydrolysis to a small extent only in the pup's stomach. The breakdown of protein is insignificant. Rat's milk contains no proteolytic enzymes.8. No significant differences in composition were found in the outer shell, the core and pyloric regions of the clot. Thus fat and casein leave the stomach in constant proportion.

Effects of early-life undernutrition in artificially reared rats: subsequent body and organ growth

“…That is, the fat content of our expressed rats' milk was extremely low, being only about one-third of that reported by Keen et al (1981). It seems likely that the principal reason for this is the 16-19 h interval between removal of the pups and milking employed here to maximize yield by volume, compared with the 2-4 h interval of Keen et al (1981), since there is evidence that lengthy interruption of suckling reduces the fat content of milk (Naismith et al 1969). It is highly likely, therefore, that our AR pups received much less fat than their MR counterparts during the 1st week or so of AR, which difference may have contributed to their poorer growth in body-weight at that time ( Fig.…”

Milk composition reflects pattern of material care in prosimian primates

“…This may explain the particularly rich milks secreted by mammals that suckle their young once a day or less, such as lagomorphs and tree shrews [D'Souza & Martin, 1974;Lhuillery et al, 1984;Martin, 1968;Oftedal, 1984;Zarrow et al, 1965]. Finally, milk that is higher in fat and protein (particularly a milk high in caseinate proteins) may produce a gastric clot that is digested more slowly, providing a more or less continuous supply of nutrients despite long intervals between suckling bouts [Hill et al, 1970;Naismith et al, 1969].…”

Fatty acid composition of liver lipids during development of rat

“…Weaning of the pups onto the SBOL diet changed at least two factors in the pups' diet: first, there was a reduction in the fat calories percentage (ca. 60% in milk [7] and 14.4% in SBOL diet), and second, weaning was associated with a restric-Liver lipid fraction tion of the dietary polyunsaturated acids to 18:2 and 18:3 only. To test the effect of wean-Total Triglycerides ing pups onto a diet containing LCP, groups of Phospholipids rats were weaned onto either the SBOL diet or a diet containing the same amount of fat, but in which some of the 18:2 and 18:3 were replaced by 20:5, 22:5, and 22:6 (Table VI).…”