The effect of constant and diurnal cyclic temperatures on performance and blood system of young turkeys

At high ambient temperature (T_a=35°C) weight gain and feed intake declined significantly. At 15°C weight gain was similar to that at 25°C, at the cost of increased feed intake. Under diurnal cyclic temperature, weight gain and feed intake were significantly lower than in the average corresponding temperature.In all treatments the turkeys’ body temperature (T_b) was at the lower level of normothemia known for broiler chickens at a similar age.The blood system compensated for changes in T_a by increasing hematocrit, hemoglobin concentration and heart muscle weight at low T_a, and by plasma expansion and increased panting at high T_a.Plasma (T₃) concentration was positively correlated with feed intake and weight gain.     

Effect of water restriction on energy and water balance and osmoregulation of the fruit bat Rousettus aegyptiacus

The energy budget, water balance and osmoregulation of the fruit bat, Rousettus aegyptiacus, were studied during normal hydration and during water restriction (oven-dried apple diet). The water input and output were balanced during both normal hydration and water restriction. The kidney of the fruit bat is well adapted to handle the water load from its fruit diet by excreting large volumes (14% of the body mass per day) of dilute urine (113±25 mosmol·kg H₂P^-1) as well as reducing urine volume (-95%) and increasing urine osmotic concentration (555±280 mosmol·kg H₂O^-1) during water restriction. The haematocrit, plasma haemoglobin and total protein concentrations did not increase during water restriction and heat exposure, suggesting the conservation of plasma volume. Gross energy intake was not alfected by water restriction. However, digested energy intake and digestibility were significantly reduced. The effective regulation of energy and water budgets during water restriction suggests that the fruit bat can cope with seasonal climatic changes and with variable fruit supply during various seasons.Abbreviations BM body mass - DEI digested energy intake - EWL evaporative water loss - GEL gross energy intake - NH normal hydration - T _a ambient temperature - WR water restriction     

Seasonal changes in daily metabolic patterns of Lacerta viridis

Summary Lacerta viridis maintained under natural photoperiodic conditions show daily and seasonal changes in metabolic rates and body temperature (T _b) as well as seasonal differences in sensitivity to temperature change. At all times of the year lizards have a daily fluctuation in oxygen consumption, with higher metabolic rates during the light phase of the day when tested at a constant ambient temperature (T _a) of 30°C. Rhythmicity of metabolic rate persists under constant darkness, but there is a decrease in the amplitude of the rhythm.Oxygen consumption measured at various T_as shows significant seasonal differences at T _as above 20°C. Expressed as the Arrhenius activation energy, metabolic sensitivity of Lacerta viridis shows temperature dependence in autumn, which changes to metabolic temperature independence in spring at T _as above 20°C. The results indicate a synergic relationship between changing photoperiod and body temperature selection, resulting in seasonal metabolic adjustment and seasonal adaptation.Abbreviations ANOVA analysis of variance - LD long day (16 h light) - SD short day (8 h light) - T _a ambient temperature - T _b body temperature     

Seasonal effects on thermoregulatory abilities of the Wahlberg's epauletted fruit bat (Epomophorus wahlbergi) in KwaZulu-Natal,South Africa

Seasonal variations in ambient temperature (T_a) require changes in thermoregulatory responses of endotherms. These responses vary according to several factors including taxon and energy constraints. Despite a plethora of studies on chiropteran variations in thermoregulation, few have examined African species. In this study, we used the Wahlberg's epauletted fruit bat (Epomophorus wahlbergi, body mass≈115 g) to determine how the thermoregulatory abilities of an Afrotropical chiropteran respond to seasonal changes in T_a. Mass specific Resting Metabolic Rates (RMR_Ta) and basal metabolic rate (BMR) were significantly higher in winter than in summer. Furthermore, winter body mass was significantly higher than summer body mass. A broad thermoneutral zone (TNZ) was observed in winter (15–35 °C) compared with summer (25–30 °C). This species exhibited heterothermy (rectal and core body temperature) during the photophase (bats' rest-phase) particularly at lower T_as and had a low tolerance of high T_as. Overall, there was a significant seasonal variation in the thermoregulatory abilities of E. wahlbergi. The relative paucity of data relating to the seasonal thermoregulatory abilities of Afrotropical bats suggest further work is needed for comparison and possible effects of climate change, particularly extreme hot days.     

Maximum rates of sustained metabolic rate in cold-exposed Djungarian hamsters (Phodopus sungorus): the second wind

Djungarian hamsters (Phodopus sungorus) tolerate short-term exposure to ambient temperatures (T _as) down to −70°C, but surprisingly, previously appeared to reach maximum sustainable metabolic rate (SusMR) when kept at T _as as high as ≥−2°C. We hypothesized that SusMR in Djungarian hamsters may be affected by the degree of prior cold acclimation and temporal patterns of T _a changes experienced by the animals, as average T _a declines. After cold-acclimation at +5°C for 6 weeks, hamsters reached rates of SusMR that were 35% higher than previously determined and were able to maintain positive energy balances down to T _a −9°C. SusMR was unaffected, however, by whether mean cold load was constant or caused by T _as cycling between +3°C and as low as −25°C, at hourly intervals. At mean T _as between +3 and −3°C hamsters significantly reduced body mass and energy expenditure, but were able to maintain stable body mass at lower T _as (−5 to −9°C). These results indicate that prior cold-acclimation profoundly affects SusMR in hamsters and that body mass regulation may play an integral part in maintaining positive energy balance during cold exposure. Because the degree of instantaneous cold load had no effect on SusMR, we hypothesize that limits to energy turnover in Djungarian hamsters are not determined by the capacity to withstand extreme temperatures (i.e., peripheral limits) but are due to central limitation of energy intake.     

Thermoregulatory responses to thermal stimulation of the preoptic anterior hypothalamus in the red fox (Vulpes vulpes)

The preoptic anterior hypothalamus (POAH) thermoregulatory controller can be characterized by two types of control, an adjustable setpoint temperature and changing POAH thermal sensitivity. Setpoint temperatures for shivering (T_shiver) and panting (T_pant) both increased with decreasing ambient temperature (T_a), and decreased with increasing T_a. The POAH controller is twice as sensitive to heating as to cooling. Metabolic rate (MR) increased during both heating and cooling of the POAH. Resting temperature of the POAH was lower than internal body temperature (T_b) at all temperatures. This indicates the presence of some form of brain cooling mechanism. Decreased T_b during POAH heating was a result of increased heat dissipation, while higher T_b during POAH cooling was a result of increased heat production and reduced heat dissipation. The surface temperature responses indicated that foxes can actively control heat flow from body surface. Such control can be achieved by increased peripheral blood flow and vasodilation during POAH heating, and reduced peripheral blood flow and vasoconstriction during POAH cooling. The observed surface temperature changes indicated that the thermoregulatory vasomotor responses can occur within l min following POAH heating or cooling. Such a degree of regulation can be achieved only by central neural control. Only surface regions covered with relatively short fur are used for heat dissipation. These thermoregulatory effective surface areas account for approximately 33% of the total body surface area, and include the area of the face, dorsal head, nose, pinna, lower legs, and paws.     

Hibernation patterns of Turkish hamsters: influence of sex and ambient temperature

Turkish hamsters (Mesocricetus brandti) are a model organism for studies of hibernation, yet a detailed account of their torpor characteristics has not been undertaken. This study employed continuous telemetric monitoring of body temperature (T _b) in hibernating male and female Turkish hamsters at ambient temperatures (T _as) of 5 and 13 °C to precisely characterize torpor bout depth, duration, and frequency, as well as rates of entry into and arousal from torpor. Hamsters generated brief intervals of short (<12 h), shallow test bouts (T _b > 20 °C), followed by deep torpor bouts lasting 4–6 days at T _a = 5 °C and 2–3 days at T _a = 13 °C. Females at T _a = 5 °C had longer bouts than males, but maintained higher torpor T _b; there were no sex differences at T _a = 13 °C. Neither body mass loss nor food intake differed between the two T _as. Hamsters entered torpor primarily during the scotophase (subjective night), but timing of arousals was highly variable. Hamsters at both T _as generated short, shallow torpor bouts between deep bouts, suggesting that this species may be capable of both hibernation and daily torpor.     

Metabolic rates,food consumption and thermoregulation in seasonal acclimatization of the Cape porcupine Hystrix africaeaustralis

Summary Metabolic rates by means of oxygen consumption (VO₂) at various ambient temperatures (T _a) and food consumption as well as water intake and thermoregulation were compared between individuals of the Cape porcupine Hystrix africaeaustralis acclimated to T _a=32°C with a photoperiod of 16L:8D summer-acclimated and T _a=10°C; 8L:16D winter-acclimated. The lower critical temperature as well as overall minimal thermal conductance were lower for the winter-acclimated porcupines when compared to summer-acclimated ones, while VO₂ at the thermoneutral-zone was significantly (P<0.001) higher in the winter-acclimated porcupines. Dry matter intake, apparent digestible dry matter intake, gross digestible energy intake, as well as water intake, were significantly higher in the winter-acclimated porcupines. Yet, while dry matter intake increased 4 times in the winter-acclimated porcupines, apparent digestible dry matter increased only at a rate of 2.9 times. This difference is better reflected in terms of digestibility efficiency which in the winter-acclimated porcupines is only at a rate of 67.5% while in the summer-acclimated porcupines it is at a rate of 90%. From the results of this study, it is possible to assume that heat production in the winter-acclimated porcupines is partly increased by food intake. Increased heat production on the one hand, and a decrease in overall minimal thermal conductance on the other, seem to be important mechanisms in winter acclimatization of the Cape porcupine.     

Comparison between the coat temperature of the eland and dairy cattle by infrared thermography

Little is known about the thermoregulatory response of the eland, a tropical animal often raised in temperate climate. We compared the surface temperature (T_s) of the eland with that of similarly sized Holstein–Friesian dairy cattle at three different ambient temperatures (T_a) to get better evidence about thermal response. The T_s of all body areas (neck, dewlap, trunk, body forepart, barrel, body hind part, forelimb and rear limb) did not differ at T_a 29.2 °C, but at T_a 12.5 °C all the areas of the eland (except the neck) had lower mean T_s than those areas in cattle. At T_a 0.4 °C, only the eland dewlap had a lower T_s and the eland neck had a higher T_s than that in cattle.     

The thermoregulatory limits of an Australian Passerine,the Silvereye (Zosterops lateralis)

(1) The thermal capabilities of Australian silvereyes (Zosterops lateralis, 11 g) were investigated both at low and high ambient temperatures (T_a) during the photophase and scotophase. (2). The peak metabolic rate (PMR) induced by helium–oxygen (79:21 %, He–O₂) exposure during the photophase was 15.64±1.55 mL O₂ g⁻¹ h⁻¹ at an effective lower survival limit T_a (T_pmr) of −39.7±6.1°C. (3). Above the thermoneutral zone (TNZ), metabolic rate, body temperature (T_b), and thermal conductance increased steeply, but they were able to withstand a T_a of 39°C. (4). Our study shows that silvereyes are able to tolerate an impressive range of T_a from about −42°C to at least +39°C and are able to produce enough heat to maintain a thermal difference between T_b and T_a of up to 80°C.     

Energy metabolism and thermoregulation in pygmy lorises (Nycticebus pygmaeus) from Yunnan Daweishan Nature Reserve

The pygmy loris (Nycticebus pygmaeus) is a small prosimian living in Vietnam, Laos, eastern Cambodia and the south part of China. In China it is only found in Pingbian, Hekou, Jinping, Luchun of Yunnan. As N. pygmaeus is seriously threatened by hunting, trade and habitat destruction, it is listed in Appendix II of CITES, and in 2006 the IUCN classified it as “vulnerable”. In order to understand the characteristics of energy metabolism and thermoregulation of N. pygmaeus, the resting metabolic rate (RMR) and body temperature (T_b) at different ambient temperature (T_a) of pygmy lorises, as well as body mass, energy intake, digestable energy intake, digestability and the thermal conductance were measured in captivity. The results obtained mainly are as follows: (1) Pygmy loris feed dry food averaged 12.90 ± 1.02 g/d. They could gain 214.87 ± 16.65 kJ/d from food intake, and earned 200.15 ± 16.36 kJ digestable energy intake per day with 90.13 ± 1.34% of the digestability. (2) The T_b at room temperatures was a little low (35.23 ± 0.16 °C) and varied with T_a from 25 °C to 35 °C. There was a positive relationship between T_b and T_a, which was described as: T_b = 27.22 + 0.34T_a (r = 0.880). (3) The resting metabolic rate (RMR) of the pygmy loris was 0.3844 ± 0.0162 mlO₂/g/h, which was 51.91 ± 1.90% of the previous predicted rate by Kleiber (1961) [21]. (4) The average thermal conductance of the pygmy loris (N. pygmaeus) was 0.0449 ± 0.0031 mlO₂/g/h/°C. These characteristics of energy metabolism and thermoregulation of N. pygmaeus in Yunnan Daweishan Nature Reserve might be considered as the adaptive characteristics to their environment in tropical semi-evergreen forests and secondary forests.     

Seasonal effects on the thermoregulation of invasive rose-ringed parakeets (Psittacula krameri)

Invasive species are a major threat to global biodiversity. Rose-ringed parakeets Psittacula krameri are widely established outside their native range and are successful invaders in many countries, including South Africa. Physiological and behavioral responses to environmental conditions are considered to be major factors that influence the abundance and distribution of birds. As rose-ringed parakeets are able to tolerate wide varieties of climatic conditions as invaders, it is important to understand their physiological responses to these. This study examined the effects of seasonal changes in ambient temperatures (T_a) on metabolic rate and body temperature (T_b) of captive-bred rose-ringed parakeets. Resting metabolic rate at various T_a and basal metabolic rate were significantly lower in winter compared to summer, and the thermo-neutral zone was broader in winter than in summer. There was no significant difference in body mass (M_b) between seasons. These parakeets showed seasonal thermoregulatory responses that represented energy conservation as expected, rather than cold tolerance. They were relatively tolerant of low T_a and showed no hypothermia at 5 °C. Our results suggest that this species is physiologically and behaviorally equipped to cope with a range of climatic situations and this partly explains their global success as an invader species.     

Effects of cortisol administration on development of the thyroid and adrenal axes in rats

Intraperitoneal (IP) injections of cortisol were administered to neonatal male rats on postnatal days 1 to 4. Plasma triiodothyronine (T₃), thyroxine (T₄) and corticosteroids were determined on days 5, 10, 13, 16, 20, 30 and 60 of age, and all animals were weighed weekly. Neonatal cortisol treatment resulted in depressed body weight gain and transient depression in plasma T₄. These results indicate that while body weight is significantly affected by cortisol treatment ontogenic patterns of plasma T₃, T₄ and corticosteroids develop normally.     

Thermoregulation in leopard tortoises in the Nama-Karoo: The importance of behaviour and core body temperatures

Despite being ectotherms, reptiles have an ability to thermoregulate which is enhanced by adopting a variety of behavioural mechanisms. Different behavioural postures, the use of retreat sites and selection of microhabitats enable reptiles to maintain their core body temperatures (T_b) above that of ambient temperatures (T_a) in winter or below T_a maximum in summer. This study describes the daily activity patterns of leopard tortoises (Stigmochelys pardalis) in relation to T_b and T_a, and the extent to which leopard tortoises can manipulate their T_b in response to seasonal changes in T_a. Ten and nine leopard tortoises were radio-tracked in 2002 and 2003, respectively and cloacal T_b and behaviours observed. Core T_bs were measured using Thermocron iButtons^™ surgically implanted into the body cavities of 4 and 5 adult telemetered tortoises for summer and winter 2003, respectively. There were seasonal differences in the extent to which certain behaviours were practiced and the time of day that these occurred. Leopard tortoises generally had unimodal activity patterns in winter and bimodal ones in summer. In winter tortoises were active at lower T_bs, and at lower T_a, than in summer. Tortoises maintained their core T_b well below T_a minimum profiles in summer and well above these in winter. Core T_b closely followed the increase in T_a minimum profiles in the mornings, however tortoises exhibited an extended thermal lag when T_a minimum profiles cooled overnight. By using different behavioural mechanisms in summer and winter, leopard tortoises maintained their core T_b at different levels compared with T_a minimum and maximum profiles. Consequently although they are ectotherms, they maintained their core T_b independent of T_a.     

Thyroid hormones increase liver and muscle thermogenic capacity in the little buntings (Emberiza pusilla)

Thyroid hormones can increase energy expenditure and stimulate basal thermogenesis by lowering metabolic efficiency. In the present study, we examined the effects of thyroid hormones on basal heat production as well as on several physiological and biochemical measures indicative of thermogenic capacity to test our hypothesis that thyroid hormones stimulate increases in thermogenesis in little buntings. Little buntings that fed on thyroxine (T₄)–laced poultry food of 3 and 5 ppm concentrations showed increases in basal metabolic rate (BMR) during the 3-week acclimation. At the end, these buntings had lower body weights, higher levels of contents of mitochondrial protein, state 4 respiration and cytochrome c oxidase activity in liver and muscle, and higher concentrations of serum triiodothyronine (T₃) and T₄ compared to control buntings. These results support the argument that thyroid hormones play an important role in the regulation of thermogenic ability in buntings by stimulating mitochondrial respiration and enzyme activities associated with aerobic metabolism.     

Ventilatory physiology of the numbat (<Emphasis Type="Italic">Myrmecobius fasciatus</Emphasis>)

This study examines the ventilatory physiology of the numbat (Myrmecobius fasciatus), a small to medium-sized (550 g) termitivorous marsupial. Ventilatory parameters at thermoneutrality reflect the slightly low (83% of predicted) basal metabolic rate of the numbat, with ventilation frequency (ƒ_R; 30.6±3.65 breaths min^–1), tidal volume [V_T; 6.0±0.66 ml at body temperature and pressure, saturated (BTPS)] and consequently minute volume (V_I; 117.7±15.22 ml min^–1; BTPS) all being 80–87% of that expected for a marsupial of similar body mass. Oxygen extraction was 27.7±1.37% in the thermoneutral zone. As is typical of marsupials, numbats accommodated increased oxygen consumption rates at ambient temperatures (T _a) below the thermoneutral zone by increasing minute volume (up to 411.2±43.98 ml min^–1; BTPS at T _a=10 °C) rather than oxygen extraction. Minute volume at 10 °C increased more by changes in ventilation frequency (up to 45.5±4.85 breaths min^–1) than tidal volume (9.4±1.03 ml, BTPS), as is also typical for a small-medium sized marsupial.Abbreviations BMR basal metabolic rate - BTPS body temperature and pressure, saturated - EO ₂ oxygen extraction - ƒ _R ventilation frequency - STPD standard temperature and pressure, dry - T _a ambient temperature - T _b body temperature - TNZ thermoneutral zone - V _I minute volume - V _T tidal volume - O ₂ oxygen consumption rate Communicated by I.D. Hume     

Ventilatory accommodation of oxygen demand and respiratory water loss in a large bird,the emu (Dromaius novaehollandiae), and a re-examination of ventilatory allometry for birds

Ventilation was studied in the emu, a large flightless bird of mass 40kg, within the range of ambient temperatures from-5 to 45°C. Data for the emu and 21 other species were used to calculate allometric relationships for resting ventilatory parameters in birds (breath frequency=13.5 mass^-0.314; tidal volume=20.7 mass^1.0). At low ambient temperatures the ventilatory system must accommodate the increased metabolic demand for oxygen. In the emu this was achieved by a combination of increased tidal volume and increased oxygen extraction. Data from emus sitting and standing at-5°C, when metabolism is 1.5x and 2.6x basal metabolic rate, respectively, indicate that at least in the emu an increase in oxygen extraction can be stimulated by low temperature independent of oxygen demand. At higher ambient temperatures ventilation was increased to facilitate respiratory water loss. The emu achieved this by increased respiratory frequency. At moderate heat loads (30–35°C) tidal volume fell. This is usually interpreted as a mechanism whereby respiratory water loss can be increased without increasing parabronchial ventilation. At 45°C tidal volume increased; however, past studies have shown that CO₂ washout is minimal under these conditions. The mechanism whereby this is possible is discussed.Abbreviations BMR basal metabolic rate - BTPS body temperature, ambient pressure, saturated - EO ₂ oxygen extraction - EWL evaporative water loss - f _R ventilation frequency - RH relative humidity - RHL respiratory heat loss - SEM standard error of the mean - SNK student-Newman-Keuls multiple range test - STPD standard temperature and pressure, dry - T _a ambient temperatures(s) - T _b body temperature(s) - T _ex expired air temperature(s) - T _rh chamber excurrent air temperature - V _J ventilation - VO₂ oxygen consumption - V _T tidal volume - V/Q air ventilation to blood perfusion ratio     

Changes in body core temperatures and heat balance after an abrupt release of lower body negative pressure in humans

Changes in body core temperature (T _cor) and heat balance after an abrupt release of lower body negative pressure (LBNP) were investigated in 5 volunteers under the following conditions: (1) an ambient temperature (T _a) of 20 °C or (2) 35 °C, and (3)T _a of 25 °C with a leg skin temperature of 30°C or (4) 35°C. The leg skin temperature was controlled with water perfusion devices wound around the legs. Rectal (T _re), tympanic (T _ty) and esophageal (T _es) temperatures, skin temperatures (7 sites) and oxygen consumption were measured. The intensity of LBNP was adjusted so that the amount of blood pooled in the legs was the same under all conditions. When a thermal balance was attained during LBNP, application of LBNP was suddenly halted. The skin temperatures increased significantly after the release of LBNP under all conditions, while oxygen consumption hardly changed. The release of LBNP caused significant falls inT _cor s under conditions (1) and (3), but loweredT _cor s very slightly under conditions (2) and (4). The changes inT _es were always more rapid and greater than those ofT _ty andT _re. The falls inT _ty andT _re appeared to be explained by changes in heat balance, whereas the sharp drop ofT _es could not be explained especially during the first 8 min after the release of LBNP. The results suggest that a fall inT _cor after a release of LBNP is attributed to an increase in heat loss due to reflexive skin vasodilation and is dependent on the temperature of venous blood returning from the lower body. It is presumed thatT _es may not be an appropriate indicator forT _cor when venous return changes rapidly.     

Oxygen dissociation of whole blood studied polarographically

The polarographic current of whole blood is in excess of that given by plasma at the same oxygen tension. The magnitude of this difference depends on (a) the oxygen content of the sample and thus is determined by the red blood cell content and by the state of oxygen saturation of hemoglobin, and (b) on the rate of dissociation of oxyhemoglobin and therefore is influenced by changes in pH, pCO₂, and temperature. The total current at 37°C. is proportional to the oxygen content of the sample and can be used to determine the latter. The theoretical basis of the studied phenomena is discussed in detail.     

Influence of Feeding Inorganic Vanadium on Growth Performance,Endocrine Variables and Biomarkers of Bone Health in Crossbred Calves

The nutritional essentialities of transition element vanadium (V) as micro-nutrient in farm animals have not yet been established, though in rat model, vanadium as vanadate has been reported to exert insulin-mimetic effect and shown to be needed for proper development of bones. The objective of this study was to determine the effect of V supplementation on growth performance, plasma hormones and bone health status in calves. Twenty-four crossbred calves (body weight 72.83 ± 2.5 kg; age 3–9 months) were blocked in four groups and randomly assigned to four treatment groups (n = 6) on body weight and age basis. Experimental animals were kept on similar feeding regimen except that different groups were supplemented with either 0, 3, 6 or 9 ppm inorganic V/kg DM. Effect of supplementation during 150-day experimental period was observed on feed intake, body weight gain, feed efficiency, body measures, endocrine variables, plasma glucose and biomarkers of bone health status. Supplementation of V did not change average daily gain (ADG), dry matter intake (DMI), feed efficiency and body measures during the experimental period. During the post-V supplementation period plasma insulin-like growth factor-1 (IGF-1), triiodothyronine (T₃) and thyroxin (T₄) concentrations were increased and observed highest in 9 mg V/kg DM fed calves; however, levels of insulin, glucose, parathyroid hormone (PTH) and calcitonin hormones remained similar among calves fed on basal or V-supplemented diets. Bone alkaline phosphatase (Bone-ALP) concentration was increased (P < 0.05); however, plasma protein tyrosine phosphatase (PTP) level decreased (P < 0.05) in 6 and 9 mg V/kg DM supplemented groups. Plasma hydroxyproline (Hyp) and tartrate-resistant acid phosphatase (TRAP) concentration were unchanged by V supplementation. Blood V concentration showed positive correlation with supplemental V levels. These results suggest that V may play a role in modulation of the action of certain endocrine variables and biomarkers of bone health status in growing crossbred calves.