%0 Journal Article
%T Proper micro-environment alleviates mortality in laboratory mouse breeding induced by litter overlap and older dams.
%A Morello GM
%A Capas-Peneda S
%A Brajon S
%A Lamas S
%A Lopes IM
%A Gilbert C
%A Olsson IAS
%J Commun Biol
%V 7
%N 1
%D 2024 Aug 17
%M 39154136
%F 6.548
%R 10.1038/s42003-024-06654-z
%X The ongoing worldwide effort to reduce animal numbers in research often omits the issue of pre-weaning mortality in mouse breeding. A conservative estimate of 20% mortality would mean approximately 1.1 M mice die annually in the EU before scientific use. We hypothesize that pre-weaning mortality in laboratory mouse breeding is associated with cage social and macro/micro-environment conditions. Here we count pups from 509 C57BL/6J litters daily for accurate detection of mortality, and monitor cage micro-environment for 172 C57BL/6J litters. Probability of pups to die increases with the increase in dam age, number and age of older pups in the cage (of overlapped/cohabitating litters), and in small (<6 pups) and large (>11 pups) focal litters. Higher temperatures (>23.6 °C) and nest scores (>3.75) compensate for some of the socially-associated risks for pup death. These findings can be implemented in strategies for reducing pre-weaning mouse mortality, a more welfare-friendly and sustainable approach for science.