Housing of pregnant rats in metabolism cages: maternal and developmental effects

The influence of the caging conditions on maternal and gestational variables was assessed for pregnant rats housed individually in two cage types. Plug-positive Sprague-Dawley females were caged either in Makrolon or in metabolism (Tecniplast) cages, and were not disturbed throughout all the gestational period. Cesarean sections were performed on gestation day 20. All live fetuses were examined for external, internal, and skeletal malformations and variations. Pregnant rats were affected by the housing system, as evidenced by a significant weight loss and reduced food consumption in the animals housed in metabolism cages. A moderate increase in the number of total skeletal defects was also observed in the fetuses of dams housed in metabolism cages. An important implication of these results would be that in maternal and developmental toxicity studies of xenobiotics, pregnant animals should not be housed in metabolism cages.