Limits to sustained energy intake. XVII. Lactation performance in MF1 mice is not programmed by fetal number during pregnancy

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SUMMARYLimits to sustained energy intake (SusEI) are important because they constrain many aspects of animal performance. Individual variability in SusEI may be imposed by genetic factors that are inherited from parents to offspring. Here, we investigated heritability of reproductive performance in MF1 mice. Food intake, milk energy output (MEO) and litter mass were measured in mothers (F 0 ) and daughters (F 1 ) that were raising litters of 10 pups. Cross-fostering was designed so that half of each litter consisted of biological offspring and the rest came from one unrelated female (i.e. fostered pups). Food intake increased linearly during early lactation and reached a plateau during late lactation (day 9-13, called the asymptotic food intake, FI AS , equivalent to SusEI). Parent-offspring regression showed that FI AS , MEO and litter mass were all positively and significantly related between mothers and their biological daughters, but no significant relationships were found between the same traits for mothers and fostered daughters. FI AS at peak lactation was significantly correlated to adult food intake and body mass when the mice were 6months old and not lactating. In conclusion, a large part of the variation in FI AS could be explained by genetic variation or maternal effects in pregnancy whereas non-genetic maternal effects in lactation were negligible. As a consequence, biological daughters of mothers with high reproductive performance (i.e. high milk production and hence higher litter mass at weaning) had a better reproductive performance themselves, independent of the mother that raised them during lactation.

Section: Discussionmentioning

confidence: 89%

Section: Discussionmentioning

confidence: 99%

Limits to sustained energy intake. XIV. Heritability of reproductive performance in mice

Vaanholt

Sinclair

Speakman

2013

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“…Because of logistical limitations, we could not manipulate litter size, which would provide a strong test for the presence of a metabolic ceiling Diamond, 1992, 1994;Johnson et al, 2001a,c;Paul et al, 2010;Simons et al, 2011;Duah et al, 2013). However, in a parallel experiment on voles from the same colony, adding two extra young to the natural litters resulted in a weaned litter size increased by only one, and a decreased mass of the weaned pups (Ołdakowski et al, 2015), which indicates that females could not adequately nurse the enlarged litters.…”

Section: Discussionmentioning

confidence: 99%

“…Rogowitz, 1998). Several experiments designed to resolve which of the two mechanisms limits females' energy budgets at peak lactation provided contradictory results (Hammond and Diamond, 1992;Speakman and McQueenie, 1996;Rogowitz, 1998;Hammond and Kristan, 2000;Johnson and Speakman, 2001;Johnson et al, 2001a,b;Wu et al, 2009;Duah et al, 2013).…”

Section: Introductionmentioning

confidence: 99%

Limits to sustained energy intake. XXIII. Does heat dissipation capacity limit the energy budget of lactating bank voles?

Sadowska

Król

Chrząścik

et al. 2016

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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 ; P<0.0001), average daily metabolic rate (shaved: 109± 2 kJ day ; 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.

“…We also observed a negative correlation between body fat content and FI AS , suggesting that females not only elevated food intake but also increased mobilisation of fat reserves to meet the highest energy demands of themselves and of their offspring (=energetic costs of lactation). However, in laboratory mice the contribution of fat to the overall energy budget is relatively trivial (Johnson et al, 2001b;Speakman, 2008) (but see Duah et al, 2013). One suggestion is that the reduction in the size of fat tissue may reduce the production of leptin and other adipokines, which then serves to stimulate food intake (Halaas et al, 1997;Abelenda et al, 2003;Speakman, 2008;Cui et al, 2011).…”

Section: Discussionmentioning

confidence: 99%

Limits to sustained energy intake. XVIII. Energy intake and reproductive output during lactation in Swiss mice raising small litters

Zhao

Song

et al. 2013

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SUMMARYLimits to sustained energy intake (SusEI) during lactation in Swiss mice have been suggested to reflect the secretory capacity of the mammary glands. However, an alternative explanation is that milk production and food intake are regulated to match the limited growth capacity of the offspring. In the present study, female Swiss mice were experimentally manipulated in two wayslitter sizes were adjusted to be between 1 and 9 pups and mice were exposed to either warm (21°C) or cold (5°C) conditions from day 10 of lactation. Energy intake, number of pups and litter mass, milk energy output (MEO), thermogenesis, mass of the mammary glands and brown adipose tissue cytochrome c oxidase activity of the mothers were measured. At 21 and 5°C, pup mass at weaning was almost independent of litter size. Positive correlations were observed between the number of pups, litter mass, asymptotic food intake and MEO. These data were consistent with the suggestion that in small litters, pup requirements may be the major factor limiting milk production. Pups raised at 5°C had significantly lower body masses than those raised at 21°C. This was despite the fact that milk production and energy intake at the same litter sizes were both substantially higher in females raising pups at 5°C. This suggests that pup growth capacity is lower in the cold, perhaps due to pups allocating ingested energy to fuel thermogenesis. Differences in observed levels of milk production under different conditions may then reflect a complex interplay between factors limiting maternal performance (peripheral limitation and heat dissipation: generally better when it is cooler) and factors influencing maximum pup growth (litter size and temperature: generally better when it is hotter), and may together result in an optimal temperature favouring reproduction.