Temperature profoundly influences physiological responses in animals, primarily due to the effects on biochemical reaction rates. Since physiological responses are often exemplified by their rate dependency (e.g., rate of blood flow, rate of metabolism, rate of heat production, and rate of ion pumping), the study of temperature adaptations has a long history in comparative and evolutionary physiology. Animals may either defend a fairly constant temperature by recruiting biochemical mechanisms of heat production and utilizing physiological responses geared toward modifying heat loss and heat gain from the environment, or utilize biochemical modifications to allow for physiological adjustments to temperature. Biochemical adaptations to temperature involve alterations in protein structure that compromise the effects of increased temperatures on improving catalytic enzyme function with the detrimental influences of higher temperature on protein stability. Temperature has acted to shape the responses of animal proteins in manners that generally preserve turnover rates at animals' normal, or optimal, body temperatures. Physiological responses to cold and warmth differ depending on whether animals maintain elevated body temperatures (endothermic) or exhibit minimal internal heat production (ectothermic). In both cases, however, these mechanisms involve regulated neural and hormonal over heat flow to the body or heat flow within the body. Examples of biochemical responses to temperature in endotherms involve metabolic uncoupling mechanisms that decrease metabolic efficiency with the outcome of producing heat, whereas ectothermic adaptations to temperature are best exemplified by the numerous mechanisms that allow for the tolerance or avoidance of ice crystal formation at temperatures below 0°C. © 2012 American Physiological Society. Compr Physiol 2:2151‐2202, 2012.

Body condition scoring of sheep was first developed as a technique in the 1960s. Unlike live weight, it circumvents the issues of skeletal size, breed and physiological state and is not influenced by gut fill or the length and wetness of the fleece. This review outlines the use of the technique and the relationships between body condition score and other physical measures. In addition, it summarises the literature, across a range of breeds and environments, on the effects of body condition score on reproductive and lactational performance, and the growth and survival of the offspring to weaning. We have proposed that while the relationship between body condition and production traits is positive, it is unlikely to be linear. Where appropriate, the review outlines areas that would benefit from further research. Finally, it outlines what a suitable body condition score profile might be for a ewe over the entire breeding cycle.

The accuracy of predictive models (also known as mechanistic or causal models) of animal responses to climate change depends on properly incorporating the principles of heat transfer and thermoregulation into those models. Regrettably, proper incorporation of these principles is not always evident. We have revisited the relevant principles of thermal physiology and analysed how they have been applied in predictive models of large mammals, which are particularly vulnerable, to climate change. We considered dry heat exchange, evaporative heat transfer, the thermoneutral zone and homeothermy, and we examined the roles of size and shape in the thermal physiology of large mammals. We report on the following misconceptions in influential predictive models: underestimation of the role of radiant heat transfer, misassignment of the role and misunderstanding of the sustainability of evaporative cooling, misinterpretation of the thermoneutral zone as a zone of thermal tolerance or as a zone of sustainable energetics, confusion of upper critical temperature and critical thermal maximum, overestimation of the metabolic energy cost of evaporative cooling, failure to appreciate that the current advantages of size and shape will become disadvantageous as climate change advances, misassumptions about skin temperature and, lastly, misconceptions about the relationship between body core temperature and its variability with body mass in large mammals. Not all misconceptions invalidate the models, but we believe that preventing inappropriate assumptions from propagating will improve model accuracy, especially as models progress beyond their current typically static format to include genetic and epigenetic adaptation that can result in phenotypic plasticity.

Two experiments were conducted to investigate the physiological responses of Bos taurus (Angus cross, n = 6) and Bos indicus (Brahman, n = 6) cattle to prolonged heat and humidity, as can occur during live export by sea. Each experiment was carried out in climate-controlled rooms, where heifers were exposed to 15 d of sustained heat and humidity. The treatment was designed to be representative of a long-haul, live-export voyage leaving a southern Australian winter and traveling to a Middle Eastern summer. Wet bulb temperature (WBT) was used to give a combined measure of dry bulb temperature and relative humidity and was increased over several days, culminating in 5 d at 32 degrees C WBT between d 7 and 11. By d 11, the respiratory rate and core body temperature increased (P < 0.001) compared with values at lower ambient temperature on d 1 and 2 when climate-controlled rooms were not operating. Feed intake of Bos taurus was reduced (P < 0.001) by d 11, whereas that of Bos indicus did not change (P = 0.14). Despite no diurnal variation in climatic conditions, core body temperature of both Bos taurus and Bos indicus continued to show a circadian amplitude of approximately 1 degrees C throughout the hottest period. This amplitude increased during the recovery period after heat was removed (up to 1.8 degrees C for Bos indicus and 1.6 degrees C for Bos taurus). Water intake for both Bos taurus and Bos indicus increased when WBT increased (P < 0.01 on d 11). Significant acid-base and blood electrolyte imbalances occurred in both Bos taurus and Bos indicus, with changes in Bos taurus being more substantial and prolonged. The increase in respiratory rate coincided with a decrease in the partial pressures of carbon dioxide and bicarbonate in venous blood. However, during the hottest period, average daily venous blood pH remained unchanged. When the heat load was reduced after d 11, the blood pH decreased, indicating metabolic acidosis. Blood pH declined from 7.44 to 7.36 for Bos taurus (P < 0.001) and from 7.44 to 7.38 for Bos indicus (P < 0.001). Other parameters measured include heart rate; packed cell volume; plasma and urine Na, K, and Cl; urine pH; and specific gravity. Our results suggest that Bos taurus cattle experience significant physiological changes during exposure to prolonged and continuous high heat and humidity, with alterations persisting for some days after the heat-stress conditions subside. Bos indicus experience similar but less pronounced physiological changes.

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Does it matter that rodents used as preclinical models of human biology are routinely housed below their thermoneutral zone? We compile evidence showing that such rodents are cold-stressed, hypermetabolic, hypertensive, sleep-deprived, obesity-resistant, fever-resistant, aging-resistant, and tumor-prone compared with mice housed at thermoneutrality. The same genotype of mouse has a very different phenotype and response to physiological or pharmacological intervention when raised below or at thermoneutrality.

In the face of climate change, the life history traits of large terrestrial mammals will prevent them from adapting genetically at a sufficient pace to keep track with changing environments, and habitat fragmentation will preclude them from shifting their distribution range. Predicting how habitat-bound large mammals will respond to environmental change requires measurement of their sensitivity and exposure to changes in the environment, as well as the extent to which phenotypic plasticity can buffer them against the changes. Behavioural modifications, such as a shift to nocturnal foraging or selection of a cool microclimate, may buffer free-living mammals against thermal and water stress, but may carry a cost, for example by reducing foraging time or increasing predation risk. Large mammals also use physiological responses to buffer themselves against changing environments, but those buffers may be compromised by a changing physical environment. A decrease in the available food energy or water leads to a trade-off in which the precision of homeothermy is relaxed, resulting in large daily fluctuations in body temperature. Understanding how large mammals prioritise competing homeostatic systems in changing environments, and the consequences of that prioritisation for their fitness, requires long-term monitoring of identifiable individual animals in their natural habitat. Although body size predicts general ecological and energetic patterns of terrestrial mammals, high intraspecific and interspecific variability means that a species-directed approach is required to accurately model responses of large mammals to climate change.

SUMMARY The alleged high net energy cost of running and low net energy cost of walking in humans have played an important role in the interpretation of the evolution of human bipedalism and the biomechanical determinants of the metabolic cost of locomotion. This study re-explores how the net metabolic energy cost of running and walking (J kg–1m–1) in humans compares to that of animals of similar mass using new allometric analyses of previously published data. Firstly, this study shows that the use of the slope of the regression between the rate of energy expenditure and speed to calculate the net energy cost of locomotion overestimates the net cost of human running. Also, the net energy cost of human running is only 17% higher than that predicted based on their mass. This value is not exceptional given that over a quarter of the previously examined mammals and birds have a net energy cost of running that is 17% or more above their allometrically predicted value. Using a new allometric equation for the net energy cost of walking, this study also shows that human walking is 20%less expensive than predicted for their mass. Of the animals used to generate this equation, 25% have a relatively lower net cost of walking compared with their allometrically predicted value. This new walking allometric analysis also indicates that the scaling of the net energy cost of locomotion with body mass is gait dependent. In conclusion, the net costs of running and walking in humans are moderately different from those predicted from allometry and are not remarkable for an animal of its size.