Nutritional Requirements for Reproduction in the Hispid Cotton Rat, Sigmodon hispidus

Abstract

To better understand resource allocation in the herbivore Sigmodon hispidus , nutritional requirements for reproduction were determined. Adult female cotton rats were fed Purina® #5001 Laboratory Chow ad lib in the laboratory. They and their progeny were sacrificed at either 10, 20, 24, or 26 days after breeding, at birth (27 days), or at weaning (39 days). Protein, lipid, and element concentrations in body tissues of pregnant females were constant. From birth to weaning, protein concentration in lactating females increased and lipid concentration decreased, whereas no concentration of elements changed significantly. In progeny, concentration of protein, K, Na, Fe, Zn, and Cu declined significantly, while concentration of lipids, Ca, P, Mg, Mn, and energy increased significantly from birth to weaning. An energy and mass-balance analysis indicated that laboratory chow easily met nutritional requirements for reproduction. This analysis was used to estimate minimum nutritional requirements for reproduction in S. hispidus . A second energy and mass-balance analysis using a natural diet indicated that protein and phosphorus ingestion by adult females was lower during autumn and winter than required for production of a litter. Thus, protein and phosphorus are critical dietary components that may limit reproduction in S. hispidus under field conditions.