Endocrine Aspects of Stress: Evaluation of Stress Reactions in Farm Animals

Abstract

Any evaluation of stress reactions must include a consideration of the kind of stress stimulus being studied as well as the kind of animal being subjected to the stress stimulus. For farm animals subjected chronically to aversive situations that cannot be alleviated through some behavioral response, an activation of primarily the hypothalamo-pituitary corticoadrenal system should be expected. Since this system is activated not only by stress stimuli, however, but is also influenced by endogenous factors giving rise to circadian and ultradian variations, these stress independent aspects of corticoadrenal activity must be determined, before any stress dependent changes can be revealed. Similarly, any evaluation of the effect of stress on an animal must include the same consideration of the type of stress stimulus and the kind of animal being studied. In animal husbandry, the effect of stress on growth, reproduction and resistance to disease is of particular interest. The possible interaction between stress reactions and the endocrine aspects of these other body functions is obvious.When studying this interaction, however, it is necessary to consider more carefully than has been done so far the biological rhythms of the hormone secretion, not only as far as the stress hormones are concerned, but also as far as other hormones are concerned.