Limits to sustained energy intake. XVI. Body temperature and physical activity of female mice during pregnancy

Abstract

SUMMARYLactation is the most energy-demanding phase of mammalian reproduction, and lactation performance may be affected by events during pregnancy. For example, food intake may be limited in late pregnancy by competition for space in the abdomen between the alimentary tract and fetuses. Hence, females may need to compensate their energy budgets during pregnancy by reducing activity and lowering body temperature. We explored the relationships between energy intake, body mass, body temperature and physical activity throughout pregnancy in the MF1 mouse. Food intake and body mass of 26 females were recorded daily throughout pregnancy. Body temperature and physical activity were monitored every minute for 23h a day by implanted transmitters. Body temperature and physical activity declined as pregnancy advanced, while energy intake and body mass increased. Compared with a pre-mating baseline period, mice increased energy intake by 56% in late pregnancy. Although body temperature declined as pregnancy progressed, this served mostly to reverse an increase between baseline and early pregnancy. Reduced physical activity may compensate the energy budget of pregnant mice but body temperature changes do not. Over the last 3days of pregnancy, food intake declined. Individual variation in energy intake in the last phase of pregnancy was positively related to litter size at birth. As there was no association between the increase in body mass and the decline in intake, we suggest the decline was not caused by competition for abdominal space. These data suggest overall reproductive performance is probably not constrained by events during pregnancy. Supplementary material available online at

Limits to sustained energy intake. XXII. Reproductive performance of two selected mouse lines with different thermal conductance

“…The asymptotic MEI in the ML line remained stable over days 13-18, consistent with studies in other mouse strains and other small rodents and lagomorphs (Johnson et al, 2001a;Król and Speakman, 2003a;Król and Speakman, 2003b;Król et al, 2003;Król et al, 2007;Wu et al, 2009;Simons et al, 2011;Zhao and Cao, 2009;Zhao et al, 2010;Vaanholt et al, 2013;Gamo et al, 2013;Yang et al, 2013;Duah et al, 2013). In contrast, the pattern observed in the MH mice was different.…”

“…These findings are consistent with previous research on food intake during lactation in different animal models. Lactating MF1 mice reach a plateau around day 11 of lactation (Johnson et al, 2001a;Król et al, 2003;Vaanholt et al, 2013;Gamo et al, 2013;Duah et al, 2013), lactating common voles on day 14 (Microtus arvalis) (Simons et al, 2011), lactating Brandt's voles Lactating mice>non-reproductive mice. Values are presented as means ± s.e.m.…”

Heat dissipation does not suppress an immune response in laboratory mice divergently selected for basal metabolic rate (BMR)

“…1B, Table 1, Table S2), which testifies to its calorigenic effect. The mean T b of immunised mice from H-BMR and L-BMR lines averaged 38.3±0.1 and 37.7±0.1°C, respectively, and was therefore comparable with T b recorded in dams during peak lactation [38.5±0.5°C in Valencak et al, 2013;38.3±0.18°C in Gamo et al, 2013a; as well as in physically active, pregnant mice (37.91±0.2°C in Gamo et al, 2013b)]. This comparison is important, because irrespective of the differences in total energy expenditure incurred by the primary metabolic challenge (in this case lactation versus immune response), the rate of co-generation of extra heat, if limiting, should be manifested as a rise in T b .…”

Limits to sustained energy intake XIX: A test of the heat dissipation limitation hypothesis in Mongolian gerbils (Meriones unguiculatus)

“…We averaged body temperature and physical activity counts over hourly periods between days 9 and 15 of infusion and then analysed these hourly data using a general linear model with infusion day (9 to 15), time of day (0 to 23) and prolactin treatment as fixed factors and individual ID as a factor nested within group to account for repeated measurements. Because we have shown previously that physical activity causes an increase in body temperature (Gamo et al, 2013), we included physical activity as a covariate in the analysis of body temperature differences. Higherlevel interactions were included.…”