Novel Bedding Material Results in Poor Pregnancy Rate with CD-1 Female Mice Used as Fosters for Producing Transgenic Mice

Abstract

The impact of a novel bedding material (cotton cloth) on the reproductive performance (pregnancy rate and production of off spring) was studied in foster females used for producing transgenic mice. Embryos injected with DNA were transferred to pseudo-pregnant foster females housed under standard conditions (aspen bedding and nesting material). Aft er embryo transfer, mice were divided between the experimental group (AGREBE cotton cloth) and control group (aspen bedding and nesting material). Pregnant mice were observed at day 15 after the transfer and the number of off spring was recorded on post-natal days 3 and 21. Altogether 116 foster mice were used as embryo recipients. Significantly more pregnancies were observed in the control group versus the experimental group: 43% and 19% of foster mice, respectively. Informal interviews with animal caretakers revealed a general dislike towards the cotton cloth (dirtier cages, mice often found on the plastic cage surface, difficult husbandry routines). The cotton cloth showed major signs of wear and tear after only a few weeks of usage. In conclusion, this study with female mice demonstrated that a cotton cloth cannot be recommended as a sole replacement for bedding and nesting material.