Thermal sweating in different body regions of sheep

1979 ◽  
Vol 92 (2) ◽  
pp. 511-512 ◽  
Author(s):  
A. K. Rai ◽  
B. S. Mehta ◽  
M. Singh
Keyword(s):  
Thermal Stress ◽  
Ambient Temperature ◽  
Heat Loss ◽  
Evaporative Cooling ◽  
Sweat Glands ◽  
Evaporative Heat Loss ◽  
Body Regions ◽  
Time Period ◽  
Sweat Production ◽  
Thermal Sweating

Although sheep combat thermal stress mainly by panting, a sizeable amount (40%) of total evaporative heat loss, is from sources other than panting (Hales & Brown, 1974). The frequency of sporadic discharge of sweat glands increases with increase in ambient temperature and is accompanied by a decline in respiration rate (Bligh, 1961). The wool coat can reduce evaporative cooling but sweating may have cooling value in sheep breeds with open fleeces (Rai, Singh & More, 1978). In sheep, the number and size of the sweat glands (Waites & Voglmayr, 1962) and the quantum of sweat production in a particular time period (Ghoshal et al. 1977) varies in different body regions. In view of the possible significance of surface evaporative cooling, thermal sweating in different body regions of sheep was investigated.

scholarly journals Sensitivity, Impact and Consequences of Changes in Respiratory Rate During Thermoregulation in Livestock – A Review

2019 ◽  
Vol 19 (2) ◽  
pp. 291-304 ◽  
Author(s):  
Buhari Habibu ◽  
Lukuman Surakat Yaqub ◽  
Tavershima Dzenda ◽  
Mohammed Umaru Kawu
Keyword(s):  
Heat Stress ◽  
Thermal Stress ◽  
Ambient Temperature ◽  
Partial Pressure ◽  
Tidal Volume ◽  
Respiratory Rate ◽  
Heat Loss ◽  
Respiratory Rhythm ◽  
Zebu Cattle ◽  
Evaporative Heat Loss

AbstractThis review discusses the thermal conservative and heat dissipating roles of one of the most sensitive thermoregulatory variables (respiratory rate) with the aim of enhancing its application in evaluating both cold and heat adaptation. During cold exposure, livestock enhance the economy of body heat through reduction in respiratory rate with the extent of reduction being greater and commencing at relatively higher ambient temperature in poorly adapted phenotypes. This is accompanied by an increase in tidal volume and alveolar oxygen uptake, but a decrease in partial pressure of oxygen. On the other hand, heat stress induces increase in respiratory rate to enhance evaporative heat loss with the magnitude of such increase being greater and commencing at relatively lower ambient temperature in phenotypes that are poorly-adapted to heat. This is accompanied by a decrease in tidal volume and the development of hypocapnia. The increase in respiratory rate is observed to be greater, moderate and lesser in livestock that are mainly (pigs, rabbits and poultry), moderately (sheep, goats and Bos taurus) and less (Zebu cattle) dependent on respiratory evaporative heat loss, respectively. The changes during chronic heat stress may cause acid-base crisis in all livestock, in addition to reduction in eggshell quality in birds; due to marked decrease in partial pressure of carbon dioxide and a compensatory increase in elimination of bicarbonate. Within and between breed variations in sensitivity of respiratory rhythm to both cold and heat stress has shown high applicability in identifying phenotypes that are more susceptible to thermal stress; with some cellular and metabolic changes occurring to protect the animal from the consequences of hypo- or hyper-thermia. The information in this review may provide basis for identification of genes that support or suppress thermoregulation and may also be of great use in animal breeding, genomics and selective thermal stress mitigation to provide maximum protection and comfort to poorly-adapted phenotypes.

scholarly journals Evaporative heat loss insufficient to attain heat balance at rest in individuals with a spinal cord injury at high ambient temperature

2019 ◽  
Vol 127 (4) ◽  
pp. 995-1004 ◽  
Author(s):  
K. E. Griggs ◽  
G. Havenith ◽  
M. J. Price ◽  
V. L. Goosey-Tolfrey
Keyword(s):  
Spinal Cord ◽  
Spinal Cord Injury ◽  
Ambient Temperature ◽  
Heat Loss ◽  
Heat Production ◽  
Heat Balance ◽  
Evaporative Cooling ◽  
Evaporative Heat Loss ◽  
Metabolic Heat ◽  
Cord Injury

The aim of the study was to determine whether climatic limits for achieving heat balance at rest are affected by spinal cord injury (SCI). Twenty-three men [8 able-bodied (AB), 8 with paraplegia (PP), and 7 with tetraplegia (TP)] rested in 37°C and 20% relative humidity (RH) for 20 min. With the ambient temperature held constant, RH was increased by 5% every 7 min, until gastrointestinal temperature (Tgi) showed a clear inflection or increased by >1°C. Tgi, skin temperatures, perceptual responses, and metabolic energy expenditure were measured throughout. Metabolic heat production [AB: 123 (21) W, PP: 111 (15) W, TP: 103 (29) W; means (SD)] and required rate of evaporative cooling for heat balance [Ereq; AB: 113 (20) W, PP: 107 (17) W, TP: 106 (29) W] were similar between groups ( P = 0.22 and P = 0.79). Compared with AB, greater increases in Tgi were observed in TP ( P = 0.01), with notable increases in mean skin temperature (Tsk) for TP and PP ( P = 0.01). A Tgi inflection point was demonstrated by seven AB, only three of eight PP, and no TP. Despite metabolic heat production (and Ereq) being similar between groups, evaporative heat loss was not large enough to obtain heat balance in TP, linked to a shortfall in evaporative cooling potential. Although PP possess a greater sweating capacity, the continual increase in Tgi and Tsk in most PP, although lower than for TP, implies that latent heat loss for PP is also insufficient to attain heat balance. NEW & NOTEWORTHY In the absence of convective heat loss, at temperatures around 37°C evaporative heat loss is insufficient to attain heat balance at rest in individuals with paraplegia and tetraplegia. This finding was directly linked to a shortfall in evaporative cooling potential compared with required evaporative cooling. In this environment, individuals with both paraplegia and tetraplegia cannot subjectively determine the magnitude of their thermal strain; thus perceptual responses should not be relied upon for this population group.

scholarly journals Evaporative cooling and water balance during flight in birds

1978 ◽  
Vol 75 (1) ◽  
pp. 231-236 ◽  
Author(s):  
J. R. Torre-Bueno
Keyword(s):  
Wind Tunnel ◽  
Water Balance ◽  
Metabolic Rate ◽  
Mass Loss ◽  
Heat Loss ◽  
Evaporative Cooling ◽  
Field Studies ◽  
Sturnus Vulgaris ◽  
Evaporative Heat Loss ◽  
Long Distance

The rate of evaporative cooling was calculated from the rate of mass loss in starlings (Sturnus vulgaris) during 90 min flights in a wind-tunnel. Evaporative heat loss ranged from 5% of the metabolic rate at −5 degrees C to 19% of the metabolic rate at 29 degrees C. Radiation and convection accounted for the balance of the heat loss. On average, starlings dehydrated during flights at all temperatures above 7 degrees C. The comparison of these results with data from field studies, which indicate that long-distance migrants do not dehydrate, suggests that migrants may maintain water balance by ascending to colder air in which convection carries off most of the heat produced.

RESPIRATORY CONTRIBUTION TO THE THERMAL BALANCE OF THE NEWBORN INFANT UNDER VARIOUS AMBIENT CONDITIONS

PEDIATRICS ◽  
1973 ◽  
Vol 51 (4) ◽  
pp. 641-650
Author(s):  
E. Sulyok ◽  
E. Jéquier ◽  
L. S. Prod'hom
Keyword(s):  
Ambient Temperature ◽  
Heat Loss ◽  
Newborn Infant ◽  
Thermal Environment ◽  
Newborn Infants ◽  
Thermal Balance ◽  
Evaporative Heat Loss ◽  
Ambient Conditions ◽  
Direct Calorimetry ◽  
Respiratory Heat Loss

The influence of environmental humidity and temperature on the thermal balance of 45 full-term newborn infants was studied by direct calorimetry within 24 hours after birth. The respiratory heat loss measured at 32C and 20% relative humidity (RH) represented 9.5% of the total heat production, and it decreased to 2.9% when RH was 80%. In neutral thermal environment (32C, 50% RH), the mean respiratory heat loss was lower than that measured during a warm exposure (36C, 50% RH), in spite of a higher absolute humidity in the latter condition. This suggests that respiration might have a thermoregulatory function during heat exposure in the newborn. Evaporative heat loss from the skin was more elevated than that from the respiratory tract, but it was less sensitive to change in ambient humidity. Convective and radiative heat losses from the skin were inversely related to ambient temperature; similarly, the metabolic rate decreased with increasing ambient temperature up to 36C. This work provides further data on the varying energy exchange between the newborn infant and his environment; it should lead to a more rational planning of infant care and caloric requirements and demonstrates the important effects of different environmental conditions on the newborn infant.

Elevated CSF osmolality inhibits thermoregulatory heat loss responses

1986 ◽  
Vol 251 (4) ◽  
pp. R749-R754 ◽  
Author(s):  
E. Turlejska ◽  
M. A. Baker
Keyword(s):  
Cerebrospinal Fluid ◽  
Body Temperature ◽  
Ambient Temperature ◽  
Heat Loss ◽  
Preoptic Area ◽  
Brain Temperature ◽  
High Ambient Temperature ◽  
Evaporative Heat Loss ◽  
Artificial Cerebrospinal Fluid ◽  
Hot Environments

The effect of intracerebroventricular (icv) infusions of hypertonic NaCl or sucrose on thermoregulatory responses to heat was studied in conscious rabbits to test the idea that brain osmoreceptors are involved in the inhibition of evaporative heat loss and elevation of body temperature in dehydrated mammals at high ambient temperature (Ta). In rabbits hydrated ad lib and resting at a Ta of 33 degrees C, icv infusion (3.4 microliter/min) of hypertonic (1,500 mosm) NaCl or sucrose in artificial cerebrospinal fluid (ACSF) produced a significant reduction in respiratory frequency (f) and in ear skin temperature (Te) and a rise in brain temperature (preoptic area, Tpoa). icv infusion of ACSF alone or ACSF + NaCl at 500 and at 750 mosm had no effect on f or on Te or Tpoa. Infusion of NaCl + ACSF at 1,000 mosm reduced f but did not affect Te or Tpoa. In hydrated rabbits, icv infusion of 1,500 mosm NaCl abolished the rise in f and in Te elicited by POA heating at Ta of 25 degrees C. In dehydrated rabbits at 33 degrees C, f was below hydrated levels and icv infusion of water (6.8 microliter/min) produced a reversible elevation in f. These findings suggest that brain osmoreceptors can influence thermoregulation in hot environments.

The effect of garment combinations on thermal comfort of office clothing

2019 ◽  
Vol 89 (21-22) ◽  
pp. 4425-4437 ◽  
Author(s):  
Hande G Atasağun ◽  
Ayşe Okur ◽  
Agnes Psikuta ◽  
René M Rossi ◽  
Simon Annaheim
Keyword(s):  
Thermal Comfort ◽  
Heat Loss ◽  
Heat Dissipation ◽  
Moisture Transfer ◽  
The Body ◽  
Raw Material ◽  
Upper Body ◽  
Thermal Manikin ◽  
Evaporative Heat Loss ◽  
Body Regions

Clothing and the enclosed air layers highly affect heat dissipation from the body and thus, are crucial factors when it comes to thermal comfort. The heat and moisture transfer is affected by the variation of the size and the shape of air gaps between the garment and the human body. In addition, the fabric and garment design properties can affect the amount of heat loss from different body parts. In this study, we investigated the effect of fabric properties (different raw materials and weave types) and the garment fit on the heat loss through the garment combinations (undershirt and shirt) for the different parts of the upper body (trunk, chest, and back) using a sweating thermal manikin. The undershirt fit and the raw material of the shirts showed strong effects on the dry thermal resistance of the garment combinations. Moreover, the undershirt properties affected the evaporative heat loss from garment combinations, and the magnitude of these effects varied over different body regions. Whilst the undershirt fit had a significant impact on the evaporative heat loss of the back region, the influence of the undershirt raw material was more important in the chest region. The findings of this study provide fundamental knowledge to improve the thermal comfort of garment combinations for office wear.

SEASONAL ACCLIMATIZATION IN VARYING HARE (LEPUS AMERICANUS)

1965 ◽  
Vol 43 (5) ◽  
pp. 731-744 ◽  
Author(s):  
J. S. Hart ◽  
Hermann Pohl ◽  
J. S. Tener
Keyword(s):  
Critical Temperature ◽  
Ambient Temperature ◽  
Heat Loss ◽  
Seasonal Changes ◽  
Evaporative Heat Loss ◽  
Total Heat Loss ◽  
Seasonal Differences ◽  
Seasonal Acclimatization ◽  
Lower Critical Temperature ◽  
Approximate Equality

Wild hares were trapped in the vicinity of Ottawa, Canada, and tested during summer and winter. After recovery from implantation of subcutaneous and substernal thermocouples, measurements of oxygen uptake and body temperatures were made during successive stepwise lowering of ambient temperature from 20 °C to −45 °C over about 5 hours. Measurements were also made during stepwise elevation of temperature from 12 °C to 38 °C over a 5-hour period and a final single test was made at 40 °C.Hares trapped during the winter had lower O2 uptake than did summer-caught hares at temperatures below thermal neutrality. The change was very similar in magnitude to the seasonal change in insulation of the fur (27% greater in winter). The lower critical temperature was shifted from +10 °C in summer hares to about −5 °C in winter hares.No seasonal differences were noted in substernal temperatures, but subcutaneous temperatures were significantly higher in winter-caught animals. Colonic temperatures were higher than substernal temperatures at all ambient temperatures.Electromyograms recorded from the mid-back showed that shivering was greater in the cold during summer than during winter in accordance with the higher O2 consumption at any given temperature. Shivering was also slightly greater during summer at the same level of O2 consumption.Varying hares showed a considerable tolerance to elevation of temperature and a capacity to maintain approximate equality of body and ambient temperature at 40 °C for some time through effective respiratory evaporative heat loss, which approached 100% of heat production. Stepwise elevation of ambient temperature did not reveal any seasonal differences in upper critical temperature (about 38 °C) or in elevation of body temperature in spite of differences in insulation of the fur. A slightly greater proportion of the total heat loss was by evaporation during the summer.Caloric intake of captive hares outdoors was similar during winter and summer. It is concluded that seasonal acclimatization in the varying hare is largely insulative with respect to cold and that changes in heat tolerance are minor if present at all. Insulative and behavioral modifications appear to compensate for seasonal changes in temperature in the Ottawa area.

scholarly journals Evaporative cooling and cutaneous surface temperature of Holstein cows in tropical conditions

2011 ◽  
Vol 40 (5) ◽  
pp. 1143-1147 ◽  
Author(s):  
Roberto Gomes da Silva ◽  
Alex Sandro Campos Maia
Keyword(s):  
Heat Loss ◽  
Coat Colour ◽  
Holstein Cows ◽  
Coefficient Of Determination ◽  
Evaporative Heat Loss ◽  
Exponential Relationship ◽  
Body Regions ◽  
Tropical Conditions ◽  
Three Body ◽  
Cutaneous Evaporation

The effects of skin temperature (T S) on the rate of heat loss by cutaneous evaporation (E S) in Holstein cows chronically exposed to sun, considering hair coat colour were studied. Sixteen purebred cows were measured for E S and T S at 01:00 p.m. after 6 hours of exposure to sun, on three body regions (flank, neck and gluteus) and considering dark and white spots separately. Sweating rate (S) and E S were measured by means of a ventilated capsule. Black skin areas presented mean S (138.9 ± 8.5 gm-2 h-1), E S (93.3 ± 5.7 Wm-2), and T S (33.1 ± 0.2°C) higher than those in the white areas (109.5 ± 9.7 gm-2h-1), 73.6 ± 6.5 Wm-2 and 32.6 ± 0.2°C, respectively). There is an exponential relationship among cutaneous temperature and cutaneous evaporation, which can be represented by the equation: E S = 31.5 + exp{(T S - 27.9)/2.19115}, with coefficient of determination r² = 0.68. Cutaneous evaporative heat loss remains almost constant around 48 Wm-2 until T S reaches nearly 31°C.

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