A concept of welfare based on reward evaluating mechanisms in the brain: anticipatory behaviour as an indicator for the state of reward systems

In this review we attempt to link the efficiency by which animals behave (e conomy of animal behaviour) to a neuronal substrate and subjective states t o arrive at a definition of animal welfare which broadens the scope of its study. Welfare is defined as the balance between positive (reward, satisfac tion) and negative (stress) experiences or affective states, The state of t his balance may range from positive (good welfare) to negative (poor welfar e). These affective states are momentary or transient states which occur ag ainst the background of and are integrated with the state of this balancing system, As will be argued the efficiency in behaviour requires that, for i nstance, satisfaction is like a moving target: reward provides the necessar y feedback to guide behaviour; it is a not steady-state which can be mainta ined for long. This balancing system is reflected in the brain by the conce rted action of opioid and mesolimbic dopaminergic systems. The state of thi s system reflects the coping capacity of the animal and is determined by pr evious events, In other words, this integrative approach of behavioural bio logy and neurobiology aims at understanding how the coping capacity of anim als may be affected and measured. We argue that this balancing system under lies the economy of behaviour, Furthermore we argue that among other techni ques anticipation in Pavlovian conditioning is an easy and useful tool to a ssess the state of this balancing system: for estimating the state of an an imal in terms of welfare we focus on the conditions when an animal is facin g a challenge, (C) 2001 Elsevier Science B.V All rights reserved.