Maternal behavior in mice selected for large litter size

Abstract

A total of 96 lactating mice and their pups from each of three replications of lines selected 21 generations for increased litter size (LS) followed by 23-25 generations of random selection and contemporary unselected control lines (LC) were characterized for maternal behavior. Sixteen dams and their pups from each replication of LS and LC lines were sampled. Litter sizes at birth for LS versus LC in the first, second, and third replicates were 17.3 versus 13.2, 15.9 versus 13.1, and 12.3 versus 10.6 pups, respectively, with LS dams averaging 2.87 ± .70 pups more. One-half of the litters were standardized to either 12 pups (Replications 1 and 2) or 8 pups (Replication 3) on day 1 of lactation; the others were not standardized. Behavioral categories included time dams spent: (1) nursing pups, (2) licking pups, (3) retrieving pups, (4) nest building, (5) resting with pups. (6) resting alone, (7) eating and drinking, (8) grooming, and (9) in other activities. Categories one through five were summed as an index of maternal behavior. Activities during 30 min observation periods from days 2 to 22 of lactation were recorded. Interactions of line by stage of lactation (days 2-4, 5-8, 9-12, 13-17, and 18-22) and line by litter standardization were not significant for any trail except time spent resting with pups (line × stage, P = 0.03).The maternal behavior index was 7.0 ± 2.2% greater (P = 0.08) for LS than LC dams. The difference was due mostly to increased time LS dams spent nursing pups (LS -LC = 9.7 ± 2.1%, P = 0.04). Averaged across lactation stages, LS dams tended to spend less time resting with their pups (-2.32 ± 1.04%, P = 0.15) than LC dams, but the difference was greatest and significant only in the last stage (-10.45 ± 2.20, P < 0.01). Selection for larger litters altered maternal behavior by increasing the time dams spent nursing pups. Interaction of line by litter size standardization existed for pup survival to weaning (P = 0.03). Survival of pups in standardized litters raised by LS dams was 10.4 ± 4.9% greater (P = 0.04) than in standardized LC litters whereas line difference in non-standardized litters was not significant (P > 0.30). Because interactions of line by litter size standardization for maternal behavior traits were not significant, correlated responses in maternal behavior were considered to be independent of size of litter being nursed.

Hypocretin‐1 Dose‐Dependently Modulates Maternal Behaviour in Mice

“…Intracerebroventricular injections (i.c.v.) of HCRT-1 Beginning 2 days after surgery (postpartum day 4), single injections were delivered each day for up to 3 consecutive days (postpartum days [4][5][6] to mice under light isoflurane anaesthesia to minimise an acute stress response. Previous studies show that mice continue to display high levels of maternal behaviour when isoflurane is used for brief anaesthetisation, indicating that this approach does not adversely affect the behaviour of interest (17,19).…”

“…Lactation involves changes in arousal and wakefulness. Lactating rats exhibit increased sleep disruptions to tend to offspring (1–4). Furthermore, lactating women experience elevated night‐time sleep disruptions and increased time awake associated with caring for offspring (5).…”

Relationship between cortisol and acute phase protein concentrations in female rabbits

“…Modern commercial rabbit breeds have large litter sizes of around 10 kits (Khalil and Baselga, 2002). Suckling of large litters involves a significant mobilisation of body reserves in female rabbits (Castellini et al, 2010) and an increase in social interaction between the mother and offspring during lactation (Chiang et al, 2002). Thus, lactation could be viewed as a relatively stressful period that might impact on subsequent reproductive performance.…”

Effects of postnatal growth restriction and subsequent catch-up growth on neurodevelopment and glucose homeostasis in rats

“…This model leads to changes in both milk intake and in growth. However, it is possible that other factors may also be changed by modifications in litter size, for example dam-pup interactions and pup-pup interactions, as seen in other rodents [ 16 , 17 ].…”