Indicators of Stress in Poultry

SummaryStress is a term which is both difficult to define and identify. Many methods have been used to try to evaluate stress in poultry and other species; they include physiological and behavioural techniques and measures of productivity. Each is discussed and its usefulness for assessing stress under field conditions is considered. It is concluded that there is no simple, unambiguous method of assessing levels of stress under field conditions.Despite the many advances in physiological techniques, practical problems still exist. Variability in hormone levels make it difficult to determine what a normal level is and many of the techniques are confined to controlled conditions in a laboratory. Behavioural measures have limitations both at a practical and at an interpretational level. Strains react differently to similar stimuli, behaviours are hard to recognize and it is difficult to know what constitutes abnormality and what is simply an adaptation to a new environment. Productivity can never safely be used as an indicator of stress. Measures of productivity are essentially economic and relate to a flock of birds, the performance of individuals being ignored. Individuals vary in their response to stresses and an acceptable level of performance cannot be taken as indicative of the absence of stress within the flock.Many of the problems of methodology may be overcome in time, but the greatest obstacle of all is that of relating these measurements to welfare and in particular, to the feelings of an animal. The enormity of this barrier may eventually prove to be too great, but if the goal is ever to be achieved a multidisciplinary approach to the problem must be adopted.