All the Pups We Cannot See: Cannibalism Masks Perinatal Death in Laboratory Mouse Breeding but Infanticide Is Rare

Perinatal mortality is a major issue in laboratory mouse breeding. We compared counting method using daily checks (DAILY_CHECK) with combining detailed video analyses to detect cannibalisms (VIDEO_TRACK) for estimating the number of C57BL/6 pups that were born, died and weaned 193 litters from trios (TRIO-OVERLAP) or without (TRIO-NO_OVERLAP) presence another litter. Linear mixed models used at litter level. To understand whether cannibalism was associated active killing (infanticide), we analysed VIDEO_TRACK recordings 109 TRIO-OVERLAP, TRIO-NO_OVERLAP SOLO (single dams). Kaplan-Meier logistic regression pup For DAILY_CHECK, mean size 35% smaller than (p < 0.0001) dead twice lower 0.0001). The risk loss higher TRIO-OVERLAP A high losses occurred between birth first cage check. Analyses data indicated clearly start most events infanticide rare. As die disappear before check, many breeding facilities are likely be unaware their real rates mortality.