Do Laboratory Mouse Females that Lose Their Litters Behave Differently around Parturition?

Abstract

Efficiency in laboratory mouse breeding is hampered by poor reproductive performance, including the loss of entire litters shortly after birth. However, the underlying mechanisms are not yet fully understood and establishing the cause of death in laboratory mouse pups can be complicated. Newborn mouse pups are generally hidden in nests, dead pups are often eaten by the female, and the widespread practice of leaving periparturient females undisturbed complicates inspection, which may delay the discovery of pup loss. In order to efficiently prevent problems with litter loss, it is important to find key factors for survival. We investigated differences in periparturient behavior between female laboratory mice whose pups survived until weaning and females whose entire litters were lost. Video recordings of 82 primiparous females of the C57BL/6 strain or knockouts with C57BL/6 background were used. The mice were observed from 24 h before until 24 h after parturition and female behaviors coded using a pre-established ethogram. The relationship between behavior and survival was analyzed using logistic models, where litter survival was regressed on the proportion of 30-s observations with at least one occurrence of the behavior. We found that females with surviving litters performed more nest building behavior during the last 24 h before parturition (p = 0.004) and spent less time outside the nest during the entire observation period (p = 0.001). Increased litter survival was also associated with more passive maternal behaviors and the female ignoring still pups less. Females that lost their litters performed more parturition-related behaviors, suggesting prolonged labor. The results indicate that maternal behavior plays a significant role in laboratory mouse pup survival. Complications at parturition also contribute to litter mortality.

Environmental enrichment prevents pup mortality in laboratory mice

“…[19][20][21] This is proven by the fact that litters from mice that spend more time building nests before parturition have an enhanced survival rate. 22 Nest building allows mice to create microclimates, which are important for preventing the nakedborn pups from cooling. Mice are highly motivated to perform nest building, as it allows the mice to shape their environment and build hiding places, which can decrease anxious behaviour, thus indicating an improved well-being.…”

Hypothalamic Gene Expression and Postpartum Behavior in a Genetic Rat Model of Depression

“…Furthermore, although WMI litters were birthed at the same rate as WLI litters, they showed a significantly lower survival rate than WLI litters. One of the potential causes of these findings could be aberrant maternal behavior of the WMI dam, as more nourishment-directed maternal behaviors are thought to increase litter survival (Weber et al, 2016). While dams of both strains show limited arched-back and blanket nursing behaviors during the observation period, WMI dams spent significantly less time with arched-back and blanket nursing of the pups than WLIs.…”

High laboratory mouse pre-weaning mortality associated with litter overlap, advanced dam age, small and large litters

“…Adults in trio cages with two litters were observed to care for their newborn pups a total of 20% less time (all the three adults together) than adults with one single litter in the cage [6], while parental investment is known to improve the chances of survival of young mice. In fact, C57BL/6 females which lost their litters entirely have been found to spend more time outside the nest and invested less time in building the nest prior to parturition [23], while the presence of males in cages with breeding females (CD-1) has been demonstrated to increase pup survival by facilitating maternal behavior [24]. Thus, reduced parental care in cages with more than one litter can be one of the mechanisms through which pup survivability is reduced in the presence of an older litter.…”