A Nest Box to Facilitate Excreta Collection From Mouse Dams Through Pregnancy, Parturition, and Lactation

Standard metabolism cages are inadequate for collecting excreta from dams during parturition because newborn pups can fall through the grating into the excreta collection area and out of reach of the dam. A nest box was designed that facilitates excreta collection from mouse dams continuously housed in metabolism cages from conception, through parturition, and into lactation and provides a safe, warm environment for pups during their first week of life. The nest box was tested by using pregnant and lactating mice of two varieties of strain 129/SvJ, metallothionein-normal and metallothionein-knockout; non-pregnant mice were used as controls. Pregnant mice (with nest box) and non-pregnant mice (without nest box) each twice received a solution of 109CdCl2 by gavage. Dams with nest boxes fastidiously urinated and defecated outside the nest box. The percentage of gavage 109Cd dose recovered in dam feces was the same after the first gavage (mean6SE, with nest box through parturition, 95%66%; n=5) as after the second gavage (mean6SE, without nest box, 95%66%; n=5). Weights and percentage weight gain of mouse dams were independent of housing conditions (metabolic cage with next box vs. conventional polycarbonate caging). Furthermore, pup growth and survival were unaffected by the inclusion of the nest box or by its removal at 1 week after birth. Therefore, the described nest box provides for the first time a way to quantitatively collect excreta from mouse dams through pregnancy, parturition, and the early postnatal period. Additional experiments are needed to test its application to other animal species and strains of mice, including those with poor mothering behavior.