A plethora of behavioural, physiological, immunophysiological, product
ion and health traits have been employed in measuring animal welfare.
Most procedures have been developed to measure stress reactions. Caref
ul interpretation is needed when considering individual measures and t
heir association with animal well-being since too little is known abou
t the physiological mechanisms and coping strategies involved in long-
term stress responses. As an alternative animal welfare has been measu
red by integrating several indices although problems arise in terms of
weighing individual indicators. Other measures, such as prepathologic
al states, that may be more closely associated with suffering or poor
welfare have not been used to a great extent. It is suggested that a h
olistic approach is taken when evaluating new housing systems for pigs
with respect to animal welfare, which combines measurement of prepath
ological states and stress reactions.