Apparent Non-Muscular Thermogenesis in Cold-Exposed Phasianid Birds
Birds maintain homeothermy during cold exposure by two mechanisms: heat loss is curtailed by behavioral/insulative adjustments and internal heat production is elevated through an increase in metabolic rate. According to the well-accepted contention, the increase in heat production in birds is accomplished by muscular shivering. This contention is based on the following facts: 1) The cold-induced increase of metabolic rate is accompanied by an increase in the electrical activity (EMG) of skeletal muscles (Steen and Enger, 1957; West, 1965), 2) A simultaneous increase in muscle-body temperature gradient occurs (Steen and Enger, 1957; Hohtola, 1982), 3) Birds lack both the anatomical substrate and the physiological mechanisms for brown-adiposetissue-type thermogenesis (see Hissa, 1988).
KeywordsHeat Production Cold Exposure Breast Muscle Muscle Temperature Major Muscle Group
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