title: Limits to sustained energy intake. XXIII. Does heat dissipation capacity limit the energy budget of lactating bank voles?
abstract: Understanding factors limiting sustained metabolic rate (SusMR) is a central issue in ecological physiology. According to the heat dissipation limit (HDL) theory, the SusMR at peak lactation is constrained by the maternal capacity to dissipate body heat. To test that theory, we shaved lactating bank voles (Myodes glareolus) to experimentally elevate their capacity for heat dissipation. The voles were sampled from lines selected for high aerobic exercise metabolism (A; characterized also by increased basal metabolic rate) and unselected control lines (C). Fur removal significantly increased the peak-lactation food intake (mass-adjusted least square means ± s.e.; shaved: 16.3 ± 0.3 g day(-1), unshaved: 14.4 ± 0.2 g day(-1); P<0.0001), average daily metabolic rate (shaved: 109 ± 2 kJ day(-1), unshaved: 97 ± 2 kJ day(-1); P<0.0001) and metabolisable energy intake (shaved: 215 ± 4 kJ day(-1), unshaved: 185 ± 4 kJ day(-1); P<0.0001), as well as the milk energy output (shaved: 104 ± 4 kJ day(-1); unshaved: 93 ± 4 kJ day(-1); P=0.021) and litter growth rate (shaved: 9.4 ± 0.7 g 4 days(-1), unshaved: 7.7 ± 0.7 g 4 days(-1); P=0.028). Thus, fur removal increased both the total energy budget and reproductive output at the most demanding period of lactation, which supports the HDL theory. However, digestive efficiency was lower in shaved voles (76.0 ± 0.3%) than in unshaved ones (78.5 ± 0.2%; P<0.0001), which may indicate that a limit imposed by the capacity of the alimentary system was also approached. Shaving similarly affected the metabolic and reproductive traits in voles from the A and C lines. Thus, the experimental evolution model did not reveal a difference in the limiting mechanism between animals with inherently different metabolic rates.
authors.affiliation: Institute of Environmental Sciences, Jagiellonian University, ul. Gronostajowa 7, Kraków 30-387, Poland edyta.sadowska@uj.edu.pl.
authors.forename: Edyta T
authors.initials: ET
authors.lastname: Sadowska
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 Environmental Sciences, Jagiellonian University, ul. Gronostajowa 7, Kraków 30-387, Poland.
authors.forename: Katarzyna M
authors.initials: KM
authors.lastname: Chrzascik
authors.affiliation: Institute of Environmental Sciences, Jagiellonian University, ul. Gronostajowa 7, Kraków 30-387, Poland.
authors.forename: Agata M
authors.initials: AM
authors.lastname: Rudolf
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, Beichen Xi Lu, Chaoyang, Beijing 100101, People's Republic of China.
authors.forename: John R
authors.initials: JR
authors.lastname: Speakman
authors.affiliation: Institute of Environmental Sciences, Jagiellonian University, ul. Gronostajowa 7, Kraków 30-387, Poland.
authors.forename: Paweł
authors.initials: P
authors.lastname: Koteja
mesh_terms: D000818:Animals; D003411:Arvicolinae / Q000502:physiology*; D001833:Body Temperature Regulation / Q000502:physiology; D004063:Digestion / Q000502:physiology; D004435:Eating; D002149:Energy Intake / Q000502:physiology; D004734:Energy Metabolism / Q000502:physiology*; D005260:Female; D006197:Hair; D007774:Lactation / Q000502:physiology*
keywords: Artificial selection; Doubly labelled water; Food consumption; Maternal investment; Milk energy output; Thermal conductance