Abstract
Lactation is the most energetically demanding physiological process that occurs in mammalian females, and as a consequence of this energy expenditure, lactating females produce an enormous amount of excess heat. This heat is thought to limit the amount of milk a mother produces, and by improving heat dissipation, females may improve their milk production and offspring quality. Here we used SKH-1 hairless mice as a natural model of improved heat dissipation. Lactating mothers were given access to a secondary cage to rest away from their pups, and this secondary cage was kept either at room temperature (22 °C) in the control rounds or cooled to 8 °C in the experimental groups. We hypothesized that the cold exposure would maximize the heat dissipation potential, leading to increased milk production and healthier pups even in the hairless mouse model. However, we found the opposite, where cold exposure allowed mothers to eat more food, but they produced smaller weight pups at the end of lactation. Our results suggest that mothers prioritize their own fitness, even if it lowers the fitness of their offspring in this particular mouse strain. This maternal–offspring trade-off is interesting and requires future studies to understand the full interaction of maternal effects and offspring fitness in the light of the heat dissipation limitation.
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Acknowledgements
Our study was made possible with the help of several students including Maria Thaler, Denise Martinkovich, Anna Mokry and Rene Haider. For his help with setting up the two-chambered cages at the Vetmeduni campus, we thank Andreas Stiedl, who swiftly adapted the cage lids to the PVC tubes. Several placement students also assisted with measurements and welfare of the animals. We thank the two anonymous reviewers for their insightful comments that greatly improved the manuscript.
Funding
JMH is partially funded by the National Institutes of Health R00AG059920. TGV was funded by P 26 246-B17 from the Austrian Science Foundation FWF during the course of the project.
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BS, JUP, SAO, and TGV designed the experiment. BS, JUP, and SAO carried out the animal work. JMH and TGV analyzed the data and made the figures. JMH and TGV wrote the first draft of the manuscript. All authors edited and approved the final manuscript.
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All experiments described in this manuscript were approved by the Ethics Committee of the University of Veterinary Medicine, Vienna, and the Austrian Ministry of Science (approval number GZ 68.205/0101-WF/V/3b/2018).
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Hoffman, J.M., Schmitz, B., Pfabe, J.U. et al. Lactating SKH-1 furless mice prioritize own comfort over growth of their pups. J Comp Physiol B 193, 453–459 (2023). https://doi.org/10.1007/s00360-023-01498-1
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DOI: https://doi.org/10.1007/s00360-023-01498-1