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Private heat for public warmth: how huddling shapes individual thermogenic responses of rabbit pups.

Gilbert C, McCafferty DJ, Giroud S, Ancel A, Blanc S - PLoS ONE (2012)

Bottom Line: Through local heating, the huddle provided each pup whatever their age with an ambient "public warmth" in the cold, which particularly benefited non-insulated pups.In this way, huddling permitted pups to effectively shift from a non-insulated to a pseudo-insulated thermal state while continuously allocating energy to growth.By providing public warmth with minimal individual costs at a stage of life when pups are the most vulnerable, huddling buffers cold challenges and ensures a constant allocation of energy to growth by reducing BAT activation.

View Article: PubMed Central - PubMed

Affiliation: Université Paris-Est, Ecole Nationale Vétérinaire d'Alfort, UMR 7179, CNRS, MNHN, Maisons-Alfort, France. cgilbert@vet-alfort.fr

ABSTRACT

Background: Within their litter, young altricial mammals compete for energy (constraining growth and survival) but cooperate for warmth. The aim of this study was to examine the mechanisms by which huddling in altricial infants influences individual heat production and loss, while providing public warmth. Although considered as a textbook example, it is surprising to note that physiological mechanisms underlying huddling are still not fully characterised.

Methodology/principal findings: The brown adipose tissue (BAT) contribution to energy output was assessed as a function of the ability of rabbit (Oryctolagus cuniculus) pups to huddle (placed in groups of 6 and 2, or isolated) and of their thermoregulatory capacities (non-insulated before 5 days old and insulated at ca. 10 days old). BAT contribution of pups exposed to cold was examined by combining techniques of infrared thermography (surface temperature), indirect calorimetry (total energy expenditure, TEE) and telemetry (body temperature). Through local heating, the huddle provided each pup whatever their age with an ambient "public warmth" in the cold, which particularly benefited non-insulated pups. Huddling allowed pups facing a progressive cold challenge to buffer the decreasing ambient temperature by delaying the activation of their thermogenic response, especially when fur-insulated. In this way, huddling permitted pups to effectively shift from a non-insulated to a pseudo-insulated thermal state while continuously allocating energy to growth. The high correlation between TEE and the difference in surface temperatures between BAT and back areas of the body reveals that energy loss for non-shivering thermogenesis is the major factor constraining the amount of energy allocated to growth in non-insulated altricial pups.

Conclusions/significance: By providing public warmth with minimal individual costs at a stage of life when pups are the most vulnerable, huddling buffers cold challenges and ensures a constant allocation of energy to growth by reducing BAT activation.

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Related in: MedlinePlus

Relationship between total energy expenditure (TEE) and body temperature of insulated and non-insulated pups, huddling in groups of 6 (G6) or placed in groups of 2 (G2), during the cold challenge.Different letters indicate significant differences. ***: significant differences with p<0.0001 between 23°C and 11°C; **: significant differences with p<0.002 between 23°C and 11°C. NS: not significant.
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pone-0033553-g001: Relationship between total energy expenditure (TEE) and body temperature of insulated and non-insulated pups, huddling in groups of 6 (G6) or placed in groups of 2 (G2), during the cold challenge.Different letters indicate significant differences. ***: significant differences with p<0.0001 between 23°C and 11°C; **: significant differences with p<0.002 between 23°C and 11°C. NS: not significant.

Mentions: Between the two sessions (at day 4 and day 5), pups gained on average 13.4±5.3 g, corresponding to a 14% increase in body mass (body mass of G6 pups at day 4: 98.9±15.9 g, of G2 pups at day 5: 112.3±18.9 g, t = −12.3, p<0.001). In the same way, between day 15 and day 16, pups gained 15.2±7.0 g, i.e. 6% of their total body mass (body mass of G6 pups at day 15: 267.6±41.7 g, of G2 pups at day 16: 282.8±43.5 g, t = −10.6, p<0.001). Hence, G2 pups, one day older than when placed in groups of six, possessed a higher body mass, i.e. a lower surface area to volume ratio than G6 pups. This may have minimised any physiological variations and effects linked to huddling.


Private heat for public warmth: how huddling shapes individual thermogenic responses of rabbit pups.

Gilbert C, McCafferty DJ, Giroud S, Ancel A, Blanc S - PLoS ONE (2012)

Relationship between total energy expenditure (TEE) and body temperature of insulated and non-insulated pups, huddling in groups of 6 (G6) or placed in groups of 2 (G2), during the cold challenge.Different letters indicate significant differences. ***: significant differences with p<0.0001 between 23°C and 11°C; **: significant differences with p<0.002 between 23°C and 11°C. NS: not significant.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3306396&req=5

pone-0033553-g001: Relationship between total energy expenditure (TEE) and body temperature of insulated and non-insulated pups, huddling in groups of 6 (G6) or placed in groups of 2 (G2), during the cold challenge.Different letters indicate significant differences. ***: significant differences with p<0.0001 between 23°C and 11°C; **: significant differences with p<0.002 between 23°C and 11°C. NS: not significant.
Mentions: Between the two sessions (at day 4 and day 5), pups gained on average 13.4±5.3 g, corresponding to a 14% increase in body mass (body mass of G6 pups at day 4: 98.9±15.9 g, of G2 pups at day 5: 112.3±18.9 g, t = −12.3, p<0.001). In the same way, between day 15 and day 16, pups gained 15.2±7.0 g, i.e. 6% of their total body mass (body mass of G6 pups at day 15: 267.6±41.7 g, of G2 pups at day 16: 282.8±43.5 g, t = −10.6, p<0.001). Hence, G2 pups, one day older than when placed in groups of six, possessed a higher body mass, i.e. a lower surface area to volume ratio than G6 pups. This may have minimised any physiological variations and effects linked to huddling.

Bottom Line: Through local heating, the huddle provided each pup whatever their age with an ambient "public warmth" in the cold, which particularly benefited non-insulated pups.In this way, huddling permitted pups to effectively shift from a non-insulated to a pseudo-insulated thermal state while continuously allocating energy to growth.By providing public warmth with minimal individual costs at a stage of life when pups are the most vulnerable, huddling buffers cold challenges and ensures a constant allocation of energy to growth by reducing BAT activation.

View Article: PubMed Central - PubMed

Affiliation: Université Paris-Est, Ecole Nationale Vétérinaire d'Alfort, UMR 7179, CNRS, MNHN, Maisons-Alfort, France. cgilbert@vet-alfort.fr

ABSTRACT

Background: Within their litter, young altricial mammals compete for energy (constraining growth and survival) but cooperate for warmth. The aim of this study was to examine the mechanisms by which huddling in altricial infants influences individual heat production and loss, while providing public warmth. Although considered as a textbook example, it is surprising to note that physiological mechanisms underlying huddling are still not fully characterised.

Methodology/principal findings: The brown adipose tissue (BAT) contribution to energy output was assessed as a function of the ability of rabbit (Oryctolagus cuniculus) pups to huddle (placed in groups of 6 and 2, or isolated) and of their thermoregulatory capacities (non-insulated before 5 days old and insulated at ca. 10 days old). BAT contribution of pups exposed to cold was examined by combining techniques of infrared thermography (surface temperature), indirect calorimetry (total energy expenditure, TEE) and telemetry (body temperature). Through local heating, the huddle provided each pup whatever their age with an ambient "public warmth" in the cold, which particularly benefited non-insulated pups. Huddling allowed pups facing a progressive cold challenge to buffer the decreasing ambient temperature by delaying the activation of their thermogenic response, especially when fur-insulated. In this way, huddling permitted pups to effectively shift from a non-insulated to a pseudo-insulated thermal state while continuously allocating energy to growth. The high correlation between TEE and the difference in surface temperatures between BAT and back areas of the body reveals that energy loss for non-shivering thermogenesis is the major factor constraining the amount of energy allocated to growth in non-insulated altricial pups.

Conclusions/significance: By providing public warmth with minimal individual costs at a stage of life when pups are the most vulnerable, huddling buffers cold challenges and ensures a constant allocation of energy to growth by reducing BAT activation.

Show MeSH
Related in: MedlinePlus