title: Sustained energy intake in lactating Swiss mice: a dual modulation process.
abstract: Limits to sustained energy intake (SusEI) during lactation are important because they provide an upper boundary below which females must trade off competing physiological activities. To date, SusEI is thought to be limited either by the capacity of the mammary glands to produce milk (the peripheral limitation hypothesis) or by a female's ability to dissipate body heat (the heat dissipation hypothesis). In the present study, we examined the effects of litter size and ambient temperature on a set of physiological, behavioral and morphological indicators of SusEI and reproductive performance in lactating Swiss mice. Our results indicate that energy input, energy output and mammary gland mass increased with litter size, whereas pup body mass and survival rate decreased. The body temperature increased significantly, while food intake (18 g day-1at 21°C versus 10 g day-1at 30°C), thermal conductance (lower by 20-27% at 30°C than 21°C), litter mass and milk energy output decreased significantly in the females raising a large litter size at 30°C compared with those at 21°C. Furthermore, an interaction between ambient temperature and litter size affected females' energy budget, imposing strong constraints on SusEI. Together, our data suggest that the limitation may be caused by both mammary glands and heat dissipation, i.e. peripheral limitation is dominant at room temperature, but heat dissipation is more significant at warm temperatures. Further, the level of the heat dissipation limits may be temperature dependent, shifting down with increasing temperature.
authors.affiliation: Department of Bioscience, College of Life and Environmental Science, Wenzhou University, Wenzhou 325035, China.
authors.forename: Jing
authors.initials: J
authors.lastname: Wen
authors.affiliation: Department of Bioscience, College of Life and Environmental Science, Wenzhou University, Wenzhou 325035, China.
authors.forename: Song
authors.initials: S
authors.lastname: Tan
authors.affiliation: Department of Bioscience, College of Life and Environmental Science, Wenzhou University, Wenzhou 325035, China.
authors.forename: Qing-Gang
authors.initials: QG
authors.lastname: Qiao
authors.affiliation: Department of Bioscience, College of Life and Environmental Science, Wenzhou University, Wenzhou 325035, China.
authors.forename: Wei-Jia
authors.initials: WJ
authors.lastname: Fan
authors.affiliation: Department of Bioscience, College of Life and Environmental Science, Wenzhou University, Wenzhou 325035, China.
authors.forename: Yi-Xin
authors.initials: YX
authors.lastname: Huang
authors.affiliation: Department of Bioscience, College of Life and Environmental Science, Wenzhou University, Wenzhou 325035, China.
authors.forename: Jing
authors.initials: J
authors.lastname: Cao
authors.affiliation: Department of Bioscience, College of Life and Environmental Science, Wenzhou University, Wenzhou 325035, China.
authors.forename: Jin-Song
authors.initials: JS
authors.lastname: Liu
authors.affiliation: Department of Psychology and Program in Neuroscience, Florida State University, Tallahassee, FL 32306-1270, USA.
authors.forename: Zuo-Xin
authors.initials: ZX
authors.lastname: Wang
authors.affiliation: Department of Bioscience, College of Life and Environmental Science, Wenzhou University, Wenzhou 325035, China zhaozj@wzu.edu.cn.
authors.forename: Zhi-Jun
authors.identifier: 0000-0001-8745-2330
authors.initials: ZJ
authors.lastname: Zhao
mesh_terms: D000818:Animals; D002149:Energy Intake; D005260:Female; D007774:Lactation; D008098:Litter Size; D051379:Mice / Q000502:physiology*; D012098:Reproduction; D013696:Temperature
keywords: Heat dissipation limits; Lactation; Litter size; Mammary gland; Sustained energy intake; Temperature