Effects of environmental temperature on heat production associated with food intake and on abdominal temperature in laying hens.

An experiment was carried out to verify the relationship between the heat production associated with food intake and environmental temperature. Four laying hens were trained to eat two meals per day and were kept under artificial illumination with dark, dim and light periods. 2. Metabolic heat production was measured using two open-circuit respiratory chambers. Abdominal temperatures were measured, using thermocouples, at environmental temperatures of 12, 16, 20, 24, 28, 32 and 36 degrees C and at food intakes of 90, 60, 30 and 0 g/d. 3. The rate of heat production was dependent on both environmental temperature and food intake. Increasing environmental temperature resulted in a decrease in total metabolic rate at any food intake, indicating that heat production associated with food intake was not directly linked with thermoregulation at low environmental temperatures. 4. Abdominal temperature varied little with either food intake or environmental temperature below 28 degrees C. Above 28 degrees C, abdominal temperature increased with both environmental temperature and quantity of food, indicating that the heat production associated with food intake adds to the heat load at high environmental temperatures. 5. Both heat production and abdominal temperature declined with decreasing light intensity and increased before feeding time. These effects were considered to result from changes in physical activity.     

Estimates of heat stress relief needs for Holstein dairy cows

Estimates of environmental heat stress are required for heat stress relief measures in cattle. Heat stress is commonly assessed by the temperature-humidity index (THI), the sum of dry and wet bulb temperatures. The THI does not include an interaction between temperature and humidity, although evaporative heat loss increases with rising air temperature. Coat, air velocity, and radiation effects also are not accounted for in the THI. The Holstein dairy cow is the primary target of heat stress relief, followed by feedlot cattle. Heat stress may be estimated for a variety of conditions by thermal balance models. The models consist of animal-specific data (BW, metabolic heat production, tissue and coat insulation, skin water loss, coat depth, and minimal and maximal tidal volumes) and of general heat exchange equations. A thermal balance simulation model was modified to adapt it for Holstein cows by using Holstein data for the animal characteristics in the model, and was validated by comparing its outputs to experimental data. Model outputs include radiant, convective, skin evaporative, respiratory heat loss and rate of change of body temperature. Effects of milk production (35 and 45 kg/d), hair coat depth (3 and 6 mm), air temperature (20 to 45 degrees C), air velocity (0.2 to 2.0 m/s), air humidity (0.8 to 3.9 kPa), and exposed body surface (100, 75, and 50%) on thermal balance outputs were examined. Environmental conditions at which respiratory heat loss attained approximately 50% of its maximal value were defined as thresholds for intermediate heat stress. Air velocity increased and humidity significantly decreased threshold temperatures, particularly at higher coat depth. The effect of air velocity was amplified at high humidity. Increasing milk production from 35 to 45 kg/d decreased threshold temperature by 5 degrees C. In the lying cow, the lower air velocity in the proximity of body surface and the smaller exposed surface markedly decrease threshold temperature. The large variation in thresholds due to environmental and animal factors justifies the use of thermal balance-based indices for estimating heat stress. Such an approach may make possible estimates of threshold temperatures at which heat stress relief is required for widely different cattle types and environmental situations.     

热应激状态下羊的体温调节

热应激是由高温环境所引起的,在炎热的气候条件下,当环境有效温度超过羊的等热区上限温度时,羊就会出现热应激。由热应激引发的不良影响广泛存在,不仅严重影响羊的生存质量,而且导致羊体温升高、生长性能降低、免疫力减弱以及肉品质下降。本文综述了导致羊产生热应激的因素以及热应激条件下的体温调节机制。在热应激的情况下,机体通过吸收环境辐射热和累积机体代谢产热,使机体获得很高的热负荷,超过了机体的散热能力。暴露在高温环境中的羊只,可通过增加机体散热消除过多的热负荷。当空气温湿度发生变化时,作为恒温动物,绵羊和山羊可以通过调整自身的产热量、采食量、饮水量、呼吸频率和行为等方式,来维持机体产热和散热的平衡。总之,羊可以利用复杂有效的散热机制维持体温平衡,适应高温环境。     

Effects of heat stress on growth, some blood variables and lipid oxidation in broilers exposed to high temperature at an early age

1. This study was conducted to determine metabolic and physiological responses of 2 commercial broiler strains, Hubbard (H) and Cobb (C), exposed to an ambient temperature of 38 degrees +/- 1 degree C for 2 h at 14 and 15 d of age. 2. Exposure to high temperature at an early age resulted in weight loss in strain C, which was not compensated for by 35 d of age but there was no weight loss in strain H. 3. Exposure of broilers to heat stress (38 degrees +/- 1 degree C) at 35 d of age resulted in an increase in rectal temperature, regardless of previously high temperature experience but acid-base balance and haematocrit values were not affected by heat stress. 4. Malondialdehyde concentration was higher in unexposed birds than in previously exposed ones and did not significantly differ between strains.     

A review of thermal stress in cattle

Cattle control body temperature in a narrow range over varying climatic conditions. Endogenous body heat is generated by metabolism, digestion and activity. Radiation is the primary external source of heat transfer into the body of cattle. Cattle homeothermy uses behavioural and physiological controls to manage radiation, convection, conduction, and evaporative exchange of heat between the body and the environment, noting that evaporative mechanisms almost exclusively transfer body heat to the environment. Cattle control radiation by shade seeking (hot) and shelter (cold) and by huddling or standing further apart, noting there are intrinsic breed and age differences in radiative transfer potential. The temperature gradient between the skin and the external environment and wind speed (convection) determines heat transfer by these means. Cattle control these mechanisms by managing blood flow to the periphery (physiology), by shelter-seeking and standing/lying activity in the short term (behaviourally) and by modifying their coats and adjusting their metabolic rates in the longer term (acclimatisation). Evaporative heat loss in cattle is primarily from sweating, with some respiratory contribution, and is the primary mechanism for dissipating excess heat when environmental temperatures exceed skin temperature (~36°C). Cattle tend to be better adapted to cooler rather than hotter external conditions, with Bos indicus breeds more adapted to hotter conditions than Bos taurus. Management can minimise the risk of thermal stress by ensuring appropriate breeds of suitably acclimatised cattle, at appropriate stocking densities, fed appropriate diets (and water), and with access to suitable shelter and ventilation are better suited to their expected farm environment.     

Consequences of short term fluctuations of environmental temperatures in calves--Part 1: Immediate reactions of the respiratory system, the cardiovascular system, metabolism and thermal regulation

Clinically healthy calves (aged 3-6 weeks) were exposed to defined ambient temperature for 4 hours (cold: 5 degrees C, 60% humidity, n = 12; warm: 35 degrees C, 60% humidity, n = 11). During the exposure of each animal in a climatic chamber, certain parameters of lung function, respiratory mechanics, blood gas analysis, circulation, metabolism and thermal regulation were registered simultaneously in order to study immediate physiological consequences of different environmental conditions. In comparison to control calves (18-20 degrees C, 60% humidity, n = 13) an insufficient adaptation of these young calves was noticed in both cold and warm conditions. At 5 degrees C, marked changes in lung function were observed, i.e. airway constriction, pulmonary hypertension, and ventilation-perfusion-mismatching leading to hypoxemia and hypercapnia. Due to compensation by the circulatory system, a sufficient O2-consumption of the organism as well as an unchanged body temperature were maintained. At 35 degrees C, the respiratory pattern changed to panting and a higher dead space ventilation. No changes were observed in pulmonary gas exchange and blood arterialisation. Due to hyperventilation, the partial pressure for CO2 decreased in blood. Since the body temperature increased continuously, thermal regulation was insufficient. This situation would have led to animals collapsing after a period of heat stress lasting longer than 4 hours. In conclusion, young calves up to the age of 6 weeks were not able to tolerate acute changes in ambient temperature. This was true for cold conditions (5 degrees C) as well as for hot conditions (35 degrees C). The results of this study should be taken into account in order to optimise transport and farming conditions.     

Cold stress induces an adrenocortical response in bottlenose dolphins (Tursiops truncatus)

Two adult bottlenose dolphins (Tursiops truncatus) were individually housed in aboveground pools over a 10-day period and exposed to decreasing water temperatures to determine whether cold stress activated the hypothalamic-pituitary-adrenal axis. To serve as controls, two additional adult dolphins were similarly housed for the same duration but at ambient water temperatures (16.8-19.6 degrees C). Across all subjects, water temperatures ranged from 4.2 to 19.6 degrees C. Voluntary blood draws were made from each dolphin every 2-3 days, and serum was analyzed via radioimmunoassay for cortisol and aldosterone. Dolphins exposed to cold water showed an increase in serum cortisol and aldosterone as temperature declined; at the coldest water exposure, cortisol was more than three times and aldosterone more than two times the levels measured at ambient temperature. Elevations occurred before the water temperature declined below the individual animal's lower critical temperature, the point at which the metabolic rate increases to compensate for the loss of body heat. Variations in corticosteroids were unrelated to the 10-day isolation period, suggesting that the response was related to the cold stress and not impacted by the isolation. Elevations in cortisol and aldosterone were lower than those observed in force captured and stranded dolphins. Although potentially related to the general adaptive stress response, elevations in cortisol and aldosterone may have other adaptive functions related to mitigating impacts resulting from cold environmental temperatures.     

Thermolability,Heat Tolerance and Renal Function In the Dassie or Hyrax,Procavia Capensis

In a series of experiments, designed to examine renal function and thermoregulation in the dassie, the following observations were made: The dassie is unable to exist indefinitely on a dry diet without water. After 8 days without water, feed intake ceases. Water consumption is relatively low, amounting to 45,7 ml/kg, which suggests efficient renal function. Faecal water loss is minimal when the animals are dehydrated. A faecal moisture value as low as 35 percent was obtained after nine days of dehydration. The capacity of the dassie kidney to concentrate electrolytes and urea is very high. The maximum recorded osmolality of the urine was 3 088 mOsm/kg, which is comparable to that of the camel. The most unusual feature of renal function in the dassie is the excretion of large amounts of undissolved calcium carbonate in the urine. The body temperature at comfortable ambient temperatures (20C) was lower than expected for a mammal of this size and may be implicated in spermatogenesis in the intra-abdominally situated testes of these animals. The dassie appears to be very thermolabile and has surprisingly low heat tolerance. Above 35C (ambient) the animals develop hyperthermia and exhibit fairly profuse nasal sweating. The upper incipient lethal temperature appears to be above 35C but less than 40C.     

Physiological reactions of three breeds of goats to cold,heat and high altitude

A total of 36 goats of the breeds Gemsfarbige Gebirgsziege (G), Saanen (S) and Toggenburger (T) were exposed for periods of 4 hours to the following climatic conditions: normal (20°C, 50% RH); cold (?5°C); heat (40°C, 30% RH) and high altitude (4000 m, 20°C, 50% RH).In the cold the animals were just able to maintain normal core temperature. Skin temperatures on the flank decreased by 3–5°C, those on the ear and the shank by 20–21°C. Respiratory rate and blood-pH decreased. The elevation in heart rate (18 beats/min) and cold shivering were indicative of a rise in heat production.In the heat, rectal temperature increased but attained a plateau at 40.7°C. Respiratory rate rose from 26 to 261 breaths/min, producing a slight respiratory alcolosis with a rise in blood-pH of 0.036 units. Heart rate augmented by 15 beats/min.At high altitude rectal temperature declined by 0.2°C, which was attributed to the quiet behaviour of the goats. There were increases in haemoglobin (+0.83 g/100 ml), haematocrit (+2.5 vol.%), erythrocyte number (+0.78 mill./mm³) and specific gravity of the blood (+0.002). The increases were considered to reflect discharge of blood from reservoirs, since they occurred within 4 hours. A rise in pH, unaccompanied by a rise in respiratory rate, pointed to an increase in tidal volume.There were suggestions of breed differences. The T-breed appeared to be relatively cold tolerant owing to the high thermal insulation of their hair coat, and also relatively heat tolerant, possibly due to their low heat production, as evidenced indirectly by their low normal heart rate (87 compared with 95 beats/min in the other two breeds).     

Effects of temperature treatments on the heat production of starving chickens

1. Heat production was measured for about 24 h at six temperatures from 2 to 35 degrees C on individually starved broilers that had been subjected to four treatments; these were acclimated or unacclimated to these temperatures, or to these temperatures for 12 h and to 22 degrees C for 12 h (alternated) during each 24-h period. 2. Response curves relating heart production and environmental temperature for the four different treatments differed significantly. Only the unacclimated birds subjected to the alternated temperatures increased heat production at 35 degrees/22 degrees C. Major effects of acclimation were observed mainly in the cold. 3. The relationship between daily endogenous nitrogen (N) excretion and heart production (mg N/kJ) was constant at the different temperatures, but acclimation and alternating temperature increased N excretion. 4. Evaporative heat loss was reduced by alternating temperature at the high temperatures, and by maintaining temperature constant in the cold.     

Respiratory alkalosis and primary hypocapnia in Labrador Retrievers participating in field trials in high-ambient-temperature conditions

OBJECTIVE: To determine whether Labrador Retrievers participating in field trials develop respiratory alkalosis and hypocapnia primarily in conditions of high ambient temperatures. ANIMALS: 16 Labrador Retrievers. PROCEDURES: At each of 5 field trials, 5 to 10 dogs were monitored during a test (retrieval of birds over a variable distance on land [1,076 to 2,200 m]; 36 assessments); ambient temperatures ranged from 2.2 degrees to 29.4 degrees C. For each dog, rectal temperature was measured and a venous blood sample was collected in a heparinized syringe within 5 minutes of test completion. Blood samples were analyzed on site for Hct; pH; sodium, potassium, ionized calcium, glucose, lactate, bicarbonate, and total CO2 concentrations; and values of PvO2 and PvCO2. Scatterplots of each variable versus ambient temperature were reviewed. Regression analysis was used to evaluate the effect of ambient temperature (< or = 21 degrees C and > 21 degrees C) on each variable. RESULTS: Compared with findings at ambient temperatures < or = 21 degrees C, venous blood pH was increased (mean, 7.521 vs 7.349) and PvCO2 was decreased (mean, 17.8 vs 29.3 mm Hg) at temperatures > 21 degrees C; rectal temperature did not differ. Two dogs developed signs of heat stress in 1 test at an ambient temperature of 29 degrees C; their rectal temperatures were higher and PvCO2 values were lower than findings in other dogs. CONCLUSIONS AND CLINICAL RELEVANCE: When running distances frequently encountered at field trials, healthy Labrador Retrievers developed hyperthermia regardless of ambient temperature. Dogs developed respiratory alkalosis and hypocapnia at ambient temperatures > 21 degrees C.     

Influence of high ambient temperatures on performance of multiparous lactating sows.

Multiparous Large White sows (n = 63) were used to investigate the effects of five ambient temperatures (18, 22, 25, 27, and 29 degrees C) and two dietary protein contents on their lactation performance. At each temperature treatment, ambient temperature was maintained constant over the 21-d lactation period. Dietary protein content was either 14 or 17% with essential amino acids levels calculated not to be limiting. The animals had ad libitum access to feed between the seventh and the 19th day of lactation. Diet composition did not influence lactation performance. Over the 21-d lactation, feed intake decreased from 5.67 to 3.08 kg/d between 18 and 29 degrees C. Between d 7 and 19, the corresponding values were 7.16 and 3.48 kg/d, respectively. This decrease was curvilinear; an equation to predict voluntary feed intake (VFI) from temperature (T, degrees C) and body weight (BW, kg) is proposed: VFI = -49,052 + 1,213 T - 31.5 T2 + 330 BW - .61 BW2 (residual standard deviation: 1,018). Skin temperature increased regularly with increased ambient temperature (34.6 to 37.4 degrees C between 18 and 29 degrees C), whereas udder temperature reached a plateau at 25 degrees C (38.3 degrees C). The gradient of temperature between skin and rectum was minimal (2 degrees C ) at 27 degrees C and remained constant at 29 degrees C. This constancy coincides with the marked reduction of feed intake. The respiratory rate increased from 26 to 124 breaths/min between 18 and 29 degrees C, and this indicates that the evaporative critical temperature was below 22 degrees C. The BW loss increased from 23 to 35 kg between 18 and 29 degrees C, but its estimated chemical composition remained constant. Pig growth rate was almost constant between 18 and 25 degrees C (241 g/d) and was reduced above 25 degrees C (212 and 189 g/d at 27 and 29 degrees C, respectively). In conclusion, temperatures above 25 degrees C seem to be critical for lactating sows in order to maintain their performance.     

Immobilization of mink (Mustela vison) with medetomidine-ketamine and remobilization with atipamezole

Four groups of mink were immobilized with medetomidine-HCl (MED) 0.1 mg/kg + ketamine (KET) 5 or 7.5 mg/kg at different ambient temperatures. The induction time, degree of immobilization and analgesia, rectal temperature, heart and respiration rates were recorded at intervals throughout the immobilization period. The animals were then given atipamezole-HCl (ATI) 0.5 mg/kg for reversal at different times after injection of MED/KET and the effects of the antagonist were evaluated.Subcutaneous administration of MED/KET induced complete immobilization in all 20 animals, and the highest dose was considered suitable for major surgery. Prolonged immobilization at low ambient temperatures (–10 to +5°C) caused severe hypothermia in all animals. The mean rectal temperature had dropped to 37.8°C and 32.1°C at 15 and 85 min, respectively, after injection of MED/KET, significantly lower than the corresponding values for animals immobilized at room temperature.Intramuscular administration of ATI 20 or 40 min after injection of MED/KET rapidly remobilized the animals without apparent side-effects. Administration of ATI to animals recovering spontaneously 90 min after injection of MED/KET induced thermogenesis (shivering) in animals immobilized at a low ambient temperature, while no such effect was seen in animals immobilized at room temperature. One hour after injection of ATI, the rectal temperatures of all treated animals had returned to normal and there were no signs of abnormal behaviour.     

Pulmonary particle deposition and airway mucociliary clearance in cold-exposed calves.

Effect of cold-induced changes in respiratory pattern on pulmonary particle deposition was investigated in 10 male Holstein calves between the ages of 1 and 3 months. Deposition of intranasally instilled fluorescence-enhanced Pasteurella haemolytica was significantly higher (P less than 0.05) for cold-exposed calves and appears to be caused by the cold-induced respiratory pattern change. Deposition was greater in apical and mediastinal lung lobes, but the reason for this preferential deposition is uncertain. Nasal mucus velocity was measured in 4 nonanesthetized calves at ambient temperature of 2 to 4 C and 16 to 18 C, using tantalum-paraffin oil droplets and serial radiography. Nasal mucus velocity was 24% lower during cold exposure. In addition, the effect of mucosal temperature on tracheal mucus velocity was determined in excised tracheas from 7 calves. A direct relationship existed between mucosal temperature and tracheal mucus velocity within the mucosal temperature range studied (35.0 to 39.5 C). Tracheal air temperature measurements in calves at ambient temperatures of -10.4 C (n = 4) and 18.5 C (n = 5) indicated that conditioning of inspired air is not complete at the tracheal level during extreme cold exposure. Therefore, cold air may directly influence tracheal mucociliary clearance. It is speculated that cold exposure increases pulmonary deposition of pathogens, while simultaneously decreasing mucociliary clearance of the upper airways, thus predisposing cold-exposed calves to respiratory tract infection.     

Thermoregulatory ability of beef heifers following intake of endophyte-infected tall fescue during controlled heat challenge

Consumption of endophyte-infected tall fescue during summer months can result in severe hyperthermia in cattle. Six heifers (296+/-8.3 kg BW) were used to determine changes in body temperature control that occur with consumption of an endophyte-infected tall fescue diet during controlled heat challenge. All animals were exposed in five separate periods to a step increase in ambient temperature (Ta) from 21 to 31 degrees C while fed E+ (5 microg ergovaline x kg(-1) x d(-1)) or endophyte-free (E-) diets. Core body temperature (Tcore) was monitored continuously using implanted, telemetric temperature transmitters. Heat production and heat loss were also measured at selected times to identify primary effects of E+ on thermal balance. Pretreatment Tcore exhibited a diurnal rhythm at a constant Ta of 21 degrees C, with high and low values at 2300 and 1300, respectively. An increase in daily averaged Tcore (P < 0.001) occurred with an increase in Ta from 21 to 31 degrees C. Likewise, all phases of the daily cycle increased equally during this challenge. This increase at 31 degrees C was associated with higher levels of respiration rate, skin temperature, respiratory vaporization, and skin vaporization (P < 0.05) and lower blood levels of thyroxine (P < 0.05). Intake of the E+ diet further elevated Tcore in heifers during the short-term heat challenge (2 d), and the effect was most pronounced at 0000 to 0300 and declined thereafter. The increase in Tcore during E+ treatment was associated with an increase in respiration rate (P < 0.05), whereas metabolic heat production, skin temperature, skin vaporization and respiratory vaporization were unaffected. These results show that consumption of an E+ diet during continuous heat challenge results in a marked increase in core body temperature, especially during nighttime exposure to heat stress, due primarily to a reduction in cutaneous heat transfer, with no effect on heat production or other measured avenues of heat loss.     

温热环境对育肥猪体温调节的影响规律

环境温湿度是影响育肥猪福利、生长及健康的重要因素。猪属于恒温动物,当环境温湿度发生变化时,可以通过调整自身的产热量、采食量、呼吸频率、皮肤温度及体核温度等指标来维持产热和散热的平衡,从而在一定温湿度范围内维持体温的恒定。本文总结和分析了育肥猪在不同环境温湿度条件下体温调节指标发生剧烈变化的顺序,判断不同温度下育肥猪的舒适状态,为今后研究、建立猪舒适环境参数,科学调控猪舍内的温热环境提供参考。     

Early-age housing temperature affects subsequent broiler chicken performance

The influence of housing temperature in early life on subsequent growth and development of broiler chickens was investigated. Hatchlings were exposed to an ambient temperature of 34 degrees C (NT) or 28 degrees C (LT) on d 1. Both temperature regimes decreased with 1 degrees C per day for 5 d. At d 6 the ambient temperature of the LT group was increased to the same ambient temperature as the NT group. At d 29 all chickens were exposed to 10 degrees C for 7 d. Navel temperature was lower in the LT group than in the NT group from d 2 to 5. Body weight of the chickens was higher in the NT group than in the LT group and the difference between both groups increased in time. Temperature treatment during the early post-hatching period did not result in a long-term alternation in organ development, haematocrit value, energy and protein metabolism or the occurrence of ascites. Although not significantly, the course of metabolism suggested that early thermal treatment had long-term effects. Before cold treatment in week 5, the NT group showed higher values for energy and protein metabolism than the LT group, but during cold exposure, the opposite was found. We concluded that exposure of chickens to a moderate reduction in house temperatures during early post-hatching life seemed to have long-term negative effects on the performance of these chickens, but, on the other hand, it seemed that these chickens were better prepared to withstand cold challenge later in life.     

Release of heat, moisture and carbon dioxide in an aviary system for laying hens.

1. Production of total heat, divided into sensible and latent heat, together with carbon dioxide and animal activity were determined at different ambient temperatures under full-scale conditions in an aviary system with loose-housed laying hens. 2. Sensible heat production decreased approximately linearly with increasing ambient temperature and was lower during the day than at night. One explanation may be that some sensible heat produced by the hens was converted to latent heat by evaporation of moisture due to increased activity of the hens during the day (scratching in the bedding and drinking/waste water). 3. Latent heat production increased with increasing ambient temperature and was higher during the day than at night. This confirms that the hens, by agitating the bedding during the day and by spilling drinking water, transferred some sensible heat to latent heat by evaporation. 4. Total heat production decreased with increasing temperature because the hens by thermoregulation decreased their metabolism in order to maintain a constant body temperature. The difference between day and night values of total heat production was less pronounced than in the case of sensible and latent heat. In comparison with current guidelines the measurements showed a higher total heat production (22% higher at 20 degrees C). 5. There was a large diurnal variation in carbon dioxide production, closely correlated to measured animal activity; on average carbon dioxide production during the 12-h dark period was only 66% of the production during the day.     

Effects of intravenous tryptophan infusion on thermoregulation in steers exposed to acute heat stress

This study was conducted to investigate the effect of tryptophan (TRP) supply on the thermoregulatory responses via brain serotonin (5‐HT) in cattle. In period 1, 12 Holstein steers were kept under a constant room temperature (22°C) and were administered the intravenous (i.v.) infusion of saline or TRP (38.5 mg/kg/2 h). Changes in rectal temperature (RT), 5‐HT concentration in the cerebrospinal fluid (CSF), and other factors involved in thermoregulation were measured. In period 2, the steers received the same treatments as in period 1; however, the room temperature was elevated from 22°C to 33°C during i.v. infusion and maintained at 33°C for 3 h. 5‐HT concentration in CSF increased following TRP infusion in both periods, and RT significantly decreased following TRP infusion only in period 2. The effect of TRP on respiration rate and plasma prolactin and total triiodothyronine concentrations was not significant. These results suggest that increase in TRP supply can attenuate increase in RT in response to acute heat stress through the increase in brain 5‐HT, followed by presumable increase in evaporative heat loss from the skin surface in cattle. It is possible that the increase in peripheral blood TRP metabolites could also participate in the hypothermic effect of TRP.     

Survey of transport environments of circus tigers (Panthera tigris).

The type of equipment used to transport circus tigers, environmental factors experienced during transport, and resultant body temperatures of tigers transported were surveyed during hot and cold weather conditions with six different circus tiger acts. Dataloggers recorded interior and exterior temperatures, relative humidity, and radiant heat at 5-min intervals during each trip. Microdataloggers fed to the tigers recorded body temperature and were recovered from eight Bengal (Panthera tigris tigris), Siberian (P. t. altaica), or Bengal-Sumatran (P. t. tigris-P. t. sumatrae) cross tigers from four different circuses. Three basic types of systems were used by circus acts to transport tigers: freestanding cages mounted on wheels that were winched or pushed into a semitrailer for transport, cages built into the trailer itself, and weather-resistant units transported on flatbed railcars or flatbed truck trailers. The highest temperature encountered inside a trailer was 37.3 degrees C in hot weather conditions, but overall, temperatures were usually between 21.1-26.7 degrees C. Temperature inside the trailers did not appear to be affected by movement and did not generally exceed ambient temperatures, indicating adequate insulation and passive ventilation. During cold weather trips, the lowest temperature inside the trailers was -1.1 degrees C, occurring during an overnight stop. Interior temperatures during cold weather transport stayed 2-6 degrees C warmer than ambient temperatures. The body temperatures of the tigers were unaffected by extreme temperatures. The only changes observed in body temperature were increases of 1-2 degrees C caused by activity and excitement associated with loading in several groups of tigers, regardless of whether it was hot or cold weather. Whenever measured, carbon monoxide and ammonia were below the detectable concentrations of 10 and 1 ppm. respectively. Overall, transport did not appear to have any adverse effects on the tigers' ability to thermoregulate.