Temperature and humidity gradients in a sheep's fleece. II. The energetic significance of transients

Gatenby, Ruth M.; Monteith, J. L.; Clark, J. A.

doi:10.1016/0002-1571(83)90042-0

Cited by 7 publications

(5 citation statements)

References 14 publications

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“…On sait qu'interviennent aussi d'autres mécanismes de réponse aux agressions du climat (Christopherson et Young, 1986), tels que la variation de l'ingestion en relation avec la variation de la thermogenèse (Bocquier et al, 1988 ;Slee et al, 1988), l'adaptation comportementale pour la recherche d'abris (Bennet et Hutchinson, 1964), l'augmentation de la thermogenèse due au transport de l'eau contenue dans la toison mouillée (jusqu'à +30% pour 10 kg d'eau d'après Gatenby et al, 1983).…”

Section: Resultsunclassified

Influence du froid, du vent et de la pluie sur les dépenses énergétiques et la thermorégulation de sept types génétiques de brebis

Hocquette¹,

Vermorel²,

Bouix³

et al. 1992

Genet. Sel. Evol.

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-La production de la chaleur de 64 brebis de 7 types génétiques d'ovins a été mesurée en chambres respiratoires pour déterminer l'influence sur leurs dépenses énergétiques, de conditions climatiques bien contrôlées simulant les intempéries rencontrées en alpage. À 15°C, en air calme, la thermogenèse des brebis est en moyenne de 3,55 kcal/kg pO , 75 par h. Une réduction de 5°C de la température ambiante ou un vent turbulent de 2 à 4 m/s entraîne une augmentation de 9% de la thermogenèse. Exposées à la pluie et au vent, les brebis s'immobilisent, la tête basse et le dos au vent. La thermogenèse des brebis Préalpes et Mourérous augmente rapidement (en 1,5 h) et fortement (+101% et +120% respectivement) et, dans une moindre mesure, celle des brebis Communes des Alpes (-+-71%). Ces races semblent cependant s'accoutumer assez rapidement aux intempéries car l'augmentation de leur thermogenèse n'est plus que de l'ordre de 40% le second jour. La thermogenèse des types génétiques Mérinos et apparentés au Mérinos («mérinisés») augmente plus lentement (en 3 à 4 h) et plus faiblement (de +22 à +78%) avec les intempéries sans réduction le deuxième jour, excepté pour les brebis F l Romanov x Mérinos d'Arles. Les brebis de souche Mérinos ont une toison très étendue, couvrant le ventre et très isolante car épaisse et dense. Les concentrations plasmatiques de triiodothyronine (T 3), * Correspondance et tirés à part : M Vermorel, INRA, Theix, 63122 Saint-Genès Champanelle thyroxine (T 4), glucose et acides gras non estérifiés augmentent de 26, 15, 8 et 56% respectivement après 2 j d'exposition aux intempéries. Les types génétiques les plus sensibles aux intempéries sont les Préalpes et les Mourérous, suivis des Communes des Alpes. Les types génétiques « mérinisés apparaissent mieux adaptés aux intempéries, spécialement les races Est à laine Mérinos et Mérinos d'Arles qui transhument. ovin/ type génétique / condition climatique / métabolisme énergétique / thermorégulation Summary-Effects of cold, wind and rain on energy expenditure and thermoregulation of ewes from 7 genetic types. Heat production (HP) and thermoregulation of 64 ewes from 7 genetic types kept in groups of !, animals in respiration chambers, were determined by indirect calorimetry to study the effects of the climatic conditions encountered in the Alps during spring and autumn. At an environmental temperature (Ta) of 15° C, without wind, HP of ewes averaged !.9 kJ!kg po. 75 /h. A reduction of Ta by 5°C or an increase of air speed to 2 to 4 M-S-1 (whirling wind) induced 9% increases in HP on average. The physical behaviour of the ewes exposed to both rain and wind at 15 or 1 if C was altered :. ' they stood motionless, back exposed to the wind and head bent downwards. HP increased in 1.5 h by 71, 101 and 120% in the Communes des Alpes, Préalpes and Mourérous ewes, respectively. These breeds seemed to adapt rapidly to these adverse climatic conditions, as the increase in HP was only about !0% on the second day. The Merdno-related breeds increased their HP more slowly (i...

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Section: Resultsunclassified

Influence du froid, du vent et de la pluie sur les dépenses énergétiques et la thermorégulation de sept types génétiques de brebis

Hocquette¹,

Vermorel²,

Bouix³

et al. 1992

Genet. Sel. Evol.

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“…Wool is highly hydrophilic, and in a sheep's fleece heat is released by condensation (equal to latent heat of vaporization) as water condenses on fibres and when water vapour is absorbed by the wool. Overall, these transient heating effects are trivial (typically less than 10 W m −2 ) because relative humidity changes slowly in the fleece and any increase in humidity near the skin is balanced by a decrease in humidity in the outer fleece [55]. Rain may increase relative humidity in the outer fleece, resulting in transient heat production, but prolonged rain will also increase heat loss by decreased insulation of the fleece and by evaporation.…”

Section: Wind and Waterproofingmentioning

confidence: 99%

Animal thermoregulation: a review of insulation, physiology and behaviour relevant to temperature control in buildings

et al. 2017

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Birds and mammals have evolved many thermal adaptations that are relevant to the bioinspired design of temperature control systems and energy management in buildings. Similar to many buildings, endothermic animals generate internal metabolic heat, are well insulated, regulate their temperature within set limits, modify microclimate and adjust thermal exchange with their environment. We review the major components of animal thermoregulation in endothermic birds and mammals that are pertinent to building engineering, in a world where climate is changing and reduction in energy use is needed. In animals, adjustment of insulation together with physiological and behavioural responses to changing environmental conditions fine-tune spatial and temporal regulation of body temperature, while also minimizing energy expenditure. These biological adaptations are characteristically flexible, allowing animals to alter their body temperatures to hourly, daily, or annual demands for energy. They exemplify how buildings could become more thermally reactive to meteorological fluctuations, capitalising on dynamic thermal materials and system properties. Based on this synthesis, we suggest that heat transfer modelling could be used to simulate these flexible biomimetic features and assess their success in reducing energy costs while maintaining thermal comfort for given building types.

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“…A fleece contains air spaces with water vapour that is in equilibrium with the water either absorbed or adsorbed on the wool fibres (Gatenby et al, 1983), with the latent heat of vaporisation of water having an important effect on the energy budget of the animal (Walsberg et al, 1978). When the skin is covered by a heavy pelage, passive transfer of water vapour across the skin is negligible.…”

Section: Temperature Within the Fleecementioning

confidence: 99%

“…The dermis also contains a prominent cutaneous vascular plexuses (Atlee et al, 1997), which may play a role in tissue resistance during heat exchange. Gatenby et al (1983) measured temperature and relative humidity in a sheep fleece of 7 cm thickness at different distances from the skin and found that on the surface of the Figure 3 Infrared thermography is an excellent non-invasive tool to measure the infrared radiation on the boundary layer of the hair coat. In non-sheared animals (right side), heat dissipation is mainly restricted to the 'thermal windows' (lighter shades at the ventral abdomen, axillary space and inside of the thighs), whereas more heat is radiated across a larger surface in sheared camelids (left side).…”

Section: Temperature Within the Fleecementioning

confidence: 99%

“…During rain, the sensible heat loss from the body is increased because the thermal insulation of the fleece is reduced as air within the fleece is displaced by water. Sheep wool has been reported to absorb a considerable amount of water (1 kg fleece is assumed to absorb 2 kg of water), with the water-absorbing capacity being modified by adherent suint and grease (Gatenby et al, 1983). However, comparable studies are lacking for lamoid fibre with its much lower content of grease.…”

Section: Temperature Within the Fleecementioning

confidence: 99%

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Relationships between integumental characteristics and thermoregulation in South American camelids

Gerken

2010

Animal

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Hair fibre is regarded as a unique mammalian feature with an important role for endothermy. Artificial selection for hair characteristics resulted in marked changes with regard to follicle number, type, distribution, growth and natural shedding. This review focuses on the fine fibre-producing South American camelids (SACs) and the relationship between their hair coat and thermoregulation. SACs have developed several special integumental characteristics. While the hair coat of the wild lamoids vicuñ a (Vicugna vicugna) and guanaco (Lama guanicoe) is formed by two types of hair (the coarse outer guard hairs and a finer undercoat), the domesticated llamas (Lama glama) and alpaca (Lama pacos) exhibit variably double coat and predominantly single coat, respectively. The distribution of the hair coat across the body is not homogenous. Thermal windows with shorter hair or thinner skin can be identified at the ventral abdomen, axillary space and inside of the thighs (about 20% of the skin), thus allowing to modulate heat dissipation. In contrast to sheep wool, lamoid fibres are mainly medullated. The thermal conductance of summer pelage was higher than that of the winter fleece and highest for the axillar and lower flanks. Lamoids have developed behavioural strategies to modify heat loss by adopting specific postures according to ambient conditions by closing or opening the thermal windows. Energy savings of 67% attributed to posture were calculated. SACs have shown to be able to adapt to a broad range of different climatic conditions. The specific integumental characteristics of SACs indicate that they have developed adaptation mechanisms particularly suited for cooler climates. Accordingly, hyperthermia might become a problem in hot, humid areas outside of their original habitat. Several studies showed the beneficial effect of shearing against heat stress. In particular, fertility in males exposed to heat stress may be improved by shearing. Infrared thermography reveals that in shorn animals the heat is radiated across the entire body surface and is not restricted to the thermal windows. However, shearing also changes the conditions of the protective layer, resulting in a loss of thermal conductance that may result in adverse effects when animals are kept under cold temperatures. The length of residual fibre appears to be crucial in avoiding excessive heat loss in a cold environment, as demonstrated by shearing experiments with different shearing machines. There is, therefore, potential for welfare considerations to conflict with industrial demands for fibre length or homogenous quality.

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Temperature and humidity gradients in a sheep's fleece. II. The energetic significance of transients

Cited by 7 publications

References 14 publications

Influence du froid, du vent et de la pluie sur les dépenses énergétiques et la thermorégulation de sept types génétiques de brebis

Influence du froid, du vent et de la pluie sur les dépenses énergétiques et la thermorégulation de sept types génétiques de brebis

Animal thermoregulation: a review of insulation, physiology and behaviour relevant to temperature control in buildings

Relationships between integumental characteristics and thermoregulation in South American camelids

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