Metabolic Rate, Thermal Insulation, and the Assessment of Environment

Abstract

“Hot” is a relative term in environmental physiology, just as it is in physics. For the newborn pig or newborn baby an environmental temperature of 32°C coupled with low air movement appears to be a “comfortable” environment, but for the mature pig or man it is “hot.” A further distinction is that under dry conditions the taxing effects of a given high temperature are greater for the pig than for man because the pig cannot sweat. “High temperature” should therefore be considered with reference not to actual temperatures but rather to particular zones of temperature. For the animal under discussion, these zones have been described in terms of thermal neutrality, least thermoregulatory effort, or comfort. These zones occur at different places on the temperature scale not only for different species but also for animals of the same species that are at different stages of development or adaptation. There has been some preliminary discussion of this subject in Chapter 1.