Gastric emptying of milk in rat pups

Gastric emptying of rat's milk in rat pups was investigated using two experimental procedures. In the first experiment pups were matched for age, body weight, and gastric contents after ingesting mother's milk in the natural suckling situation. Then the pups were placed in one of three different environmental conditions for the test period. They were killed at 0, 2, or 4 h, and their gastric contents were weighed. The results revealed a very consistent gastric emptying process across ages, regardless of the presence or absence of the dam or moderate alterations in the environment. Gastric volume appeared to be the only factor affecting the rate of gastric emptying. In the second experiment gastric emptying was investigated in fasted pups after intubation with one of several volumes of rat's milk. Pups were killed at 0, 1, 2, or 4 h after gavage, and their gastric contents were weighed. The results indicate that the rate of gastric emptying is directly related to the immediate gastric volume. The emptying process is described as exponential, but the distribution of halftime values indicates the kinetics are not strictly first order. The volume-related effect on gastric emptying rate also correlated highly with the volume-related suppression of ingestion reported in a previous study. A model of gastric emptying is proposed for infant mammals.