The effect of a desert climate on the lactation and on the fertility of the nursing rat

Exposure to high temperatures (heatwaves) is rapidly emerging as an important issue of climate change, in particular for female mammals during lactation. High temperatures adversely affect the ability to dissipate heat, which has negative effects on reproductive output. The cumulative effects on growth of F1 offspring after weaning, and future reproductive performance of offspring, remain uncertain. In this study, F1 mice weaned from mothers lactating at 21 and 32.5°C were housed at 21°C from day 19 until day 56 of age, during which food intake and body mass were measured. The F1 adult females that were weaned at the two temperatures were bred and then exposed to 32.5°C during lactation. Energy intake and milk output, and litter size and mass, were determined. The F1 adults weaned at 32.5°C consumed less food and had lower body mass than their counterparts weaned at 21°C. Several visceral organs or reproductive tissues were significantly lower in mass in F1 weaned at 32.5°C than at 21°C. The exposure to 32.5°C significantly decreased energy intake, milk output and litter mass in F1 adult females during lactation. The F1 adult females weaned at 32.5°C produced less milk and raised lighter pups than those previously weaned at 21°C. The data suggest that transient exposure to hot temperatures during lactation has longlasting impacts on offspring, including stunted growth and decreases in future reproductive performance when adult. This indicates that the offspring of females previously experiencing hot temperatures have a significant fitness disadvantage.

Section: Discussionsupporting

confidence: 82%

Exposure to hot temperatures during lactation stunted offspring growth and decreased the future reproductive performance of female offspring

Bao

Chen

Hambly

et al. 2020

“…These have included the 'central limitation hypothesis', which suggests that energy budgets are limited by the capacity of the alimentary tract to absorb and process food; the 'metabolic theory of ecology', which suggests that metabolic rates are limited by the geometry of the fractal supply network distributing absorbed resources to their sites of use; the 'peripheral limitation hypothesis', suggesting that total demand is a sum of the demands of individual tissues in the periphery, each working under unique physiological constraints; and the 'heat dissipation limitation (HDL) theory', which suggests that the constraining factor is the capacity to dissipate body heat and risk of hyperthermia (reviewed in Speakman and Król, 2005;Speakman and Król, 2011;Piersma and van Gils, 2010). Varying the ambient temperature experienced by animals during lactation has repeatedly shown that female animals modulate their intake at peak lactation in relation to the prevailing ambient temperature (Hammond et al, 1994;Jansen and Binard, 1991;Johnson and Speakman, 2001;Hammond and Kristan, 2000;Leon and Woodside, 1983;Morag et al, 1969;Rogowitz, 1998;Wu et al, 2009;Zhang and Wang, 2007). Such data are incompatible with, and hence disprove, the central limitation hypothesis and the metabolic theory of ecology, but are consistent with the two other ideas -the peripheral limitation hypothesis and the HDL theory.…”

Section: Introductionmentioning

confidence: 82%

Limits to sustained energy intake XX: body temperatures and physical activity of female mice during lactation

Gamo

Troup

Mitchell

et al. 2013

SUMMARYLactating animals consume greater amounts of food than non-reproductive animals, but energy intake appears to be limited in late lactation. The heat dissipation limit theory suggests that the food intake of lactating mice is limited by the capacity of the mother to dissipate heat. Lactating mice should therefore have high body temperatures (T b ), and changes in energy intake during lactation should be reflected by variation in T b . To investigate these predictions, 26 mice (Mus musculus) were monitored daily throughout lactation for food intake, body mass, litter size and litter mass. After weaning, 21days postpartum, maternal food intake and body mass were monitored for another 10days. Maternal activity and T b were recorded every minute for 23h a day using implanted transmitters (vital view). Energy intake increased to a plateau in late lactation (days 13-17). Daily gain in pup mass declined during this same period, suggesting a limit on maternal energy intake. Litter size and litter mass were positively related to maternal energy intake and body mass. Activity levels were constantly low, and mice with the largest increase in energy intake at peak lactation had the lowest activity. T b rose sharply after parturition and the circadian rhythm became compressed within a small range. T b during the light period increased considerably (1.1°C higher than in baseline), and lactating mice faced chronic hyperthermia, despite their activity levels in lactation being approximately halved. Average T b increased in relation to energy intake as lactation progressed, but there was no relationship between litter size or litter mass and the mean T b at peak lactation. These data are consistent with the heat dissipation limit theory, which suggests performance in late lactation is constrained by the ability to dissipate body heat. Supplementary material available online at

“…In both species, relieving heat loss by either cooling the floor (sows) (Silva et al, 2006) or spraying with water (dairy cattle) (Igono et al, 1985) decreased body temperature and increased milk production. Exposure to high temperatures (close to 30°C) during lactation has also been shown to decrease pup growth in lab strains of rats (Rattus norvegicus) Heat dissipation in the common vole (Jansen and Binard, 1991;Leon and Woodside, 1983;Morag et al, 1969). By contrast, data that do not support the theory include the observation that cold exposure (10°C) did not increase milk production and retarded pup growth in cotton rats (Sigmodon hispidus) (Rogowitz, 1998), and shaving did not elevate milk production or pup growth in Swiss mice (Zhao and Cao, 2009;Zhao et al, 2010).…”

Section: Introductionmentioning

confidence: 99%

Ambient temperature shapes reproductive output during pregnancy and lactation in the common vole (Microtus arvalis): a test of the heat dissipation limit theory

Simons

Reimert

Vinne

et al. 2011

SUMMARYThe heat dissipation limit theory suggests that heat generated during metabolism limits energy intake and, thus, reproductive output. Experiments in laboratory strains of mice and rats, and also domestic livestock generally support this theory. Selection for many generations in the laboratory and in livestock has increased litter size or productivity in these animals. To test the wider validity of the heat dissipation limit theory, we studied common voles (Microtus arvalis), which have small litter sizes by comparison with mice and rats, and regular addition of wild-caught individuals of this species to our laboratory colony ensures a natural genetic background. A crossover design of ambient temperatures (21 and 30°C) during pregnancy and lactation was used. High ambient temperature during lactation decreased milk production, slowing pup growth. The effect on pup growth was amplified when ambient temperature was also high during pregnancy. Shaving fur off dams at 30°C resulted in faster growth of pups; however, no significant increase in food intake and or milk production was detected. With increasing litter size (natural and enlarged), asymptotic food intake during lactation levelled off in the largest litters at both 21 and 30°C. Interestingly, the effects of lactation temperature on pup growth where also observed at smaller litter sizes. This suggests that vole dams trade-off costs associated with hyperthermia during lactation with the yield from investment in pup growth. Moreover, pup survival was higher at 30°C, despite lower growth, probably owing to thermoregulatory benefits. It remains to be seen how the balance is established between the negative effect of high ambient temperature on maternal milk production and pup growth (and/or future reproduction of the dam) and the positive effect of high temperatures on pup survival. This balance ultimately determines the effect of different ambient temperatures on reproductive success.