title: Limits to sustained energy intake. XXII. Reproductive performance of two selected mouse lines with different thermal conductance.
abstract: Maximal sustained energy intake (SusEI) appears limited, but the factors imposing the limit are disputed. We studied reproductive performance in two lines of mice selected for high and low food intake (MH and ML, respectively), and known to have large differences in thermal conductance (29% higher in the MH line at 21°C). When these mice raised their natural litters, their metabolisable energy intake significantly increased over the first 13 days of lactation and then reached a plateau. At peak lactation, MH mice assimilated on average 45.3% more energy than ML mice (222.9±7.1 and 153.4±12.5 kJ day(-1), N=49 and 24, respectively). Moreover, MH mice exported on average 62.3 kJ day(-1) more energy as milk than ML mice (118.9±5.3 and 56.6±5.4 kJ day(-1), N=subset of 32 and 21, respectively). The elevated milk production of MH mice enabled them to wean litters (65.2±2.1 g) that were on average 50.2% heavier than litters produced by ML mothers (43.4±3.0 g), and pups that were on average 27.2% heavier (9.9±0.2 and 7.8±0.2 g, respectively). Lactating mice in both lines had significantly longer and heavier guts compared with non-reproductive mice. However, inconsistent with the 'central limit hypothesis', the ML mice had significantly longer and heavier intestines than MH mice. An experiment where the mice raised litters of the opposing line demonstrated that lactation performance was not limited by the growth capacity of offspring. Our findings are consistent with the idea that the SusEI at peak lactation is constrained by the capacity of the mothers to dissipate body heat.
authors.affiliation: Institute of Biological and Environmental Sciences, University of Aberdeen, Aberdeen AB24 2TZ, UK Department of Physiology, College of Medicine, University of Karbala, PO Box 1069, Karbala, Iraq.
authors.forename: Aqeel H
authors.initials: AH
authors.lastname: Al Jothery
authors.affiliation: Institute of Biological and Environmental Sciences, University of Aberdeen, Aberdeen AB24 2TZ, UK.
authors.forename: Elżbieta
authors.initials: E
authors.lastname: Król
authors.affiliation: Institute of Biological and Environmental Sciences, University of Aberdeen, Aberdeen AB24 2TZ, UK.
authors.forename: James
authors.initials: J
authors.lastname: Hawkins
authors.affiliation: Institute of Biological and Environmental Sciences, University of Aberdeen, Aberdeen AB24 2TZ, UK.
authors.forename: Aurore
authors.initials: A
authors.lastname: Chetoui
authors.affiliation: Institute of Biological and Environmental Sciences, University of Aberdeen, Aberdeen AB24 2TZ, UK.
authors.forename: Alexander
authors.initials: A
authors.lastname: Saint-Lambert
authors.affiliation: Institute of Biological and Environmental Sciences, University of Aberdeen, Aberdeen AB24 2TZ, UK.
authors.forename: Yuko
authors.initials: Y
authors.lastname: Gamo
authors.affiliation: Institute of Biological and Environmental Sciences, University of Aberdeen, Aberdeen AB24 2TZ, UK.
authors.forename: Suzanne C
authors.initials: SC
authors.lastname: Shaw
authors.affiliation: Institute of Biological and Environmental Sciences, University of Aberdeen, Aberdeen AB24 2TZ, UK Institute of Genetics and Developmental Biology, State Key Laboratory of Molecular Developmental Biology, Chinese Academy of Sciences, Bei Chen Xi Lu, Chaoyang, Beijing 100101, People's Republic of China Research Institute of Wildlife Ecology, University of Veterinary Medicine, A-1160 Vienna, Austria.
authors.forename: Teresa
authors.initials: T
authors.lastname: Valencak
authors.affiliation: Animal and Veterinary Science Group, Scotland's Rural College (SRUC), Edinburgh EH9 3JG, UK.
authors.forename: Lutz
authors.initials: L
authors.lastname: Bünger
authors.affiliation: Institute of Evolutionary Biology, University of Edinburgh, Edinburgh EH9 3JT, UK.
authors.forename: William G
authors.initials: WG
authors.lastname: Hill
authors.affiliation: Institute of Biological and Environmental Sciences, University of Aberdeen, Aberdeen AB24 2TZ, UK.
authors.forename: Lobke M
authors.initials: LM
authors.lastname: Vaanholt
authors.affiliation: Institute of Biological and Environmental Sciences, University of Aberdeen, Aberdeen AB24 2TZ, UK.
authors.forename: Catherine
authors.initials: C
authors.lastname: Hambly
authors.affiliation: Institute of Biological and Environmental Sciences, University of Aberdeen, Aberdeen AB24 2TZ, UK Institute of Genetics and Developmental Biology, State Key Laboratory of Molecular Developmental Biology, Chinese Academy of Sciences, Bei Chen Xi Lu, Chaoyang, Beijing 100101, People's Republic of China j.speakman@abdn.ac.uk.
authors.forename: John R
authors.initials: JR
authors.lastname: Speakman
mesh_terms: D000818:Animals; D001833:Body Temperature Regulation / Q000502:physiology*; D001835:Body Weight; D002149:Energy Intake / Q000502:physiology*; D004734:Energy Metabolism; D005260:Female; D007422:Intestines / Q000033:anatomy & histology / Q000502:physiology; D007774:Lactation / Q000502:physiology*; D008297:Male; D051379:Mice; D008892:Milk
keywords: Artificial selection; Cross-fostering; Daily energy expenditure; Heat dissipation limit; Lactation; Milk production