ABSTRACT
This chapter describes the mechanisms used by animals to protect the thermal stability of the internal environment in face of fluctuations in ambient, or environmental, temperature. In stress, animals divert their resources so that the corrective mechanisms receive priority. Other activities, such as the productive functions so important in animal agriculture—growth, fiber production, reproduction, and lactation—are compromised until the stress is alleviated. Animals are well protected from the environment at large by the amazing integumentary organ system, the skin. A complete analysis of interactions between animals and their environment involves consideration of metabolism, homeostasis, homeorhesis, climatology, thermodynamics, behavior, stress, and adaptation. The subdiscipline called thermoregulatory physiology attempts to deal with all of these aspects. Animals lose heat to the environment through two basic mechanisms: sensible and insensible. Heat production, or metabolic rate, bears a complex relationship to ambient temperature. The process of acclimation starts with an acute response to the environmental change, then gradual changes start to occur.
