Effects of Pregnancy and Lactation on the Mineral Appetites of Wild Rabbits [Oryctolagus cuniculus (L.)]

Abstract

The appetite of wild rabbits [Oryctolagus cuniculus (L.)] for 500 mEq/1 solutions of NaCl, KC1, CaCl2 and MgCl2 was studied during pregnancy and lactation. The animals were individually caged and external Na+ balances were made. Under control conditions, there was little intake of NaCl. During pregnancy there was a rise in intake. In the latter state it was highest and was increased nearly 10-fold. During lactation the intake of NaCl solution was even greater, often representing daily turnover of total extracellular content of Na+. The increase in individual animals was related to litter size. The voluntary intake of KC1 and CaCl2 was also increased in pregnancy and lactation. The daily water intake more than doubled during lactation. Food intake decreased in pregnancy, particularly during the latter stages, but was increased during lactation. The metabolic balance study showed that the increased intake of NaCl solution in pregnancy and lactation was not caused by sequestration of Na+ in the tissues of the developing young during pregnancy, or Na+ loss during lactation causing a body deficit which was thereupon corrected by increased voluntary intake. In both instances intake increased without any preceding fall in urinary output, and was greatly in excess of a feasible demand for Na+ for the fetus or lactation. The results raise some interesting new possibilities in relation to hormonal, pheremone or sensory factors in the stimulation of appetite for salt. (Endocrinology88: 31, 1971)