Self-selection of calcium during pregnancy and lactation in rats.

A modification of the two-choice diet paradigm was used to determine whether female rats would self-select high levels of calcium at different times in a reproductive episode. A 2 X 2 X 5 (reproductive state X diet X time) design was used to compare the relative calcium intake of impregnated and non-impregnated rats given ad lib access to a calcium deficient or calcium sufficient diet together with demineralised water and a 2.4% calcium lactate solution over five weeks. For the impregnated groups, this time period comprised three weeks of pregnancy and two weeks of lactation. The results showed that during lactation the impregnated animals maintained on the calcium deficient diet consumed a greater amount of calcium solution relative to water intake than any other group. This increase in relative calcium solution intake occurred early in lactation and appeared not to correlate with increases in milk production.