Limits to sustained energy intake XXVII: trade-offs between first and second litters in lactating mice support the ecological context hypothesis

Abstract

Increased reproductive effort may lead to trade-offs with future performance and impact offspring, thereby influencing optimal current effort level. We experimentally enlarged or reduced litter size in mice during their first lactation, and then followed them through a successive unmanipulated lactation. Measurements of food intake, body mass, milk energy output (MEO), litter size and litter mass were taken. Offspring from the first lactation were also bred to investigate their reproductive success. In their first lactation, mothers with enlarged litters (=9, 16 pups) weaned significantly smaller pups, culled more pups, and increased MEO and food intake compared with mothers with reduced litters (=9, 5 pups). In the second lactation, no significant differences in pup mass or litter size were observed between groups, but mothers that had previously reared enlarged litters significantly decreased pup mass, MEO and food intake compared with those that had reared reduced litters. Female offspring from enlarged litters weaned slightly smaller pups than those from reduced litters, but displayed no significant differences in any of the other variables measured. These results suggest that females with enlarged litters suffered from a greater energetic burden during their first lactation, and this was associated with lowered performance in a successive reproductive event and impacted on their offspring's reproductive performance. Female 'choice' about how much to invest in the first lactation may thus be driven by trade-offs with future reproductive success. Hence, the 'limit' on performance may not be a hard physiological limit. These data support the ecological context hypothesis.

Limits to Sustained Energy Intake XXXI: Effect of Graded Levels of Dietary Fat on Lactation Performance in Swiss Mice

“…Furthermore, an interaction of heat dissipation and peripheral limitation was also supported by several studies, suggesting that the limitation is dominated by different factors under different ambient temperature conditions (Speakman and Król, 2011;Zhao et al, 2016;Wen et al, 2017). An alternative 'trade-off' idea suggests that mammals may not maximise their lactation performance under all conditions, particularly if maximizing performance during the present reproduction would have a detrimental effect on their future reproductive performance or survival (Speakman and Król, 2005b;Piersma, 2011;Vaanholt et al, 2018).…”

Limits to sustained energy intake XXVIII: Beneficial effects of high dietary fat on lactation performance in mice

“…The physiological basis of mechanisms imposing limits on E max during reproduction has been the matter of much debate (Drent and Daan, 1980;Hammond and Diamond, 1992;Koteja, 1996;Krol et al, 2007;Rogowitz, 1998;Wu et al, 2009). Several theories have been advanced to explain the apparent limits on E max (Hammond et al, 1996;Krol and Speakman, 2003a,b;Vaanholt et al, 2018;Wen et al, 2017). The two theories most supported by the current data are the 'peripheral limitations' theory Hammond and Kristan, 2000;Koteja, 1996;Rogowitz, 1998) and the 'heat dissipation limitation' (HDL) theory (Sadowska et al, 2016;Simons et al, 2011;Wu et al, 2009;Yang et al, 2013), or a combination thereof (Speakman and Król, 2011;Wen et al, 2017).…”

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

“…From an evolutionary perspective, a small litter is less worth investing in than a larger litter: Maestripieri and Alleva [ 43 ] demonstrated that CD-1 dams of large litters (eight pups) spent more than twice as much time displaying litter defense behaviors against intruder males than dams of small litters (four pups). The increase in pup death probability found in litters of 12 pups and above, on the other hand, may be a result of increased sibling competition for access to milk, as discussed above, and also may represent a ceiling in milk production capacity by the dams [ 22 , 44 , 45 ].…”