By Holly Webb, ASAS/ASAP communications intern
Animal Production 2016 speaker highlight: Alan Tilbrook
When investigating stress, measures of glucocorticoid blood concentration levels are commonly used. However, even in conjunction with behavioural or physiological measures, it is difficult to use measures of circulating glucocorticoids to assess the welfare or health status of an animal.
In an invited review recently published in the Journal of Animal Science, Dr Cameron Ralph and Prof. Alan Tilbrook from South Australian Research and Development Institute (SARDI) and The University of Adelaide, discuss the usefulness of measures of glucocorticoids (corticosterone in birds and rodents and cortisol in all other mammals) in the assessment of animal welfare.
The article describes the need for knowledge about the inputs that cause an increase in circulating concentrations of stress hormones, before using glucocorticoids as a measure to assess animal welfare. Authors highlight doubts about the usefulness of glucocorticoids and how they relate to the assessment of the animal welfare.
It is difficult to assess the welfare of an animal as the actions of glucocorticoids will impact behaviour and physiology and seldom can these be evaluated from blood concentrations alone. Also, different stimuli can result in similar stress responses, yet rarely can these be interpreted from peripheral measures and typical of endocrine hormones, stress hormones often have more than one function.
When assessing welfare, normal non-stress related glucocorticoid functions or the complex mechanism that regulates the effects of glucocorticoids are rarely considered. Increased glucocorticoid synthesis can indicate positive welfare states and a stress response may actually increase fitness and improve the welfare of the animal.
Authors further discuss animal welfare under the biological functioning and affective states frameworks, highlighting the dynamic interactions between both frameworks. The use of stress hormones to assess their affective state is challenging as both positive and negative emotional states can induce stress responses, making interpretation from measuring the end-point hormones virtually impossible.
The full article ‘INVITED REVIEW: The usefulness of measuring glucocorticoids for assessing animal welfare’, can be accessed here.