INVITED REVIEW: The usefulness of measuring glucocorticoids for assessing animal welfare
Publication Type: |
Journal Article |
Year of Publication: |
2016 |
Authors: |
C. R. Ralph, A. J. Tilbrook |
Publication/Journal: |
Journal of Animal Science |
Keywords: |
11-beta-hydroxysteroid dehydrogenase type-1, agriculture, amygdaloid complex, corticosteroid-binding globulin, corticosterone, cortisol, dairy & animal science, electrical-stimulation, free serum, isolation/restraint stress, luteinizing-hormone, pituitary-adrenal axis, plasma corticosteroids, stress responses, tissue cortisol activity, welfare assessment |
ISBN: |
0021-8812 |
Abstract:
Glucocorticoids (corticosterone in birds and rodents and cortisol in all other mammals) are glucoregulatory hormones that are synthesized in response to a range of stimuli including stress and are regularly measured in the assessment of animal welfare. Glucocorticoids have many normal or non-stress-related functions, and glucocorticoid synthesis can increase in response to pleasure, excitement, and arousal as well as fear, anxiety, and pain. Often, when assessing animal welfare, little consideration is given to normal non-stress-related glucocorticoid functions or the complex mechanisms that regulate the effects of glucocorticoids on physiology. In addition, it is rarely acknowledged that increased glucocorticoid synthesis can indicate positive welfare states or that a stress response can increase fitness and improve the welfare of an animal. In this paper, we review how and when glucocorticoid synthesis increases, the actions mediated through type I and type II glucocorticoid receptors, the importance of corticosteroid-binding globulin, the role of 11 beta-hydroxysteroid dehydrogenase, and the key aspects of neurophysiology relevant to activating the hypothalamo-pituitary-adrenal axis. This is discussed in the context of animal welfare assessment, particularly under the biological functioning and affective states frameworks. We contend that extending the assessment of animal welfare to key brain regions afferent to the hypothalamus and incorporating the aspects of glucocorticoid physiology that affect change in target tissue will advance animal welfare science and inspire more comprehensive assessment of the welfare of animals.