Abstract
Animals are exploited by man for several different purposes. According to many, society should be concerned about the welfare of these animals. Currently, an increasing need exists to be able to assess and improve animal welfare. In this thesis a concept of welfare is applied that states that 'welfare is
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determined by the balance between positive and negative experiences'. This definition implies that an interaction exists between stress- and reward systems in the brain and that negative experiences can be compensated by positive experiences.
This thesis describes a study that investigates whether the spontaneous behavioural response that animals display when they expect a reward (anticipatory behaviour) can be used as a welfare indicator. This concept is based on existing knowledge about the influence of previous experiences such as stress on the sensitivity for rewards in both man and animals. The response (i.e. sensitivity) to rewards can therefore be indicative of previous experiences and may therefore be a tool to assess the state of an animal in terms of welfare. In this study the rat is used as a model and reward-sensitivity is determined by anticipatory behaviour which is evoked in this animal by classical conditioning. This means that through regular pairings of a stimulus (sound and/or light) with the arrival of a reward, the animal will form an association between this stimulus and the reward. Subsequently, the animal will display anticipatory behaviour at the presentation of the stimulus. This behavioural response can be investigated in the interval between the announcement and the actual arrival of the reward and is characterised by an increase in activity. This anticipatory increase in activity is determined by means of the analysis of the total frequency of all displayed behavioural elements.
The results show that previous experiences influence anticipatory behaviour for a reward and, thus, that this spontaneous behavioural response may serve as a welfare indicator. Furthermore, it became apparent that regular reward-announcements can counteract the consequences of stress. Interestingly, a reward in the form of an enriched cage (cage with several objects to increase the possibilities for species-specific behaviour) could even reverse the effects of chronic stress (depressive-like symptoms).
Summarizing, the results described in this thesis indicate that announcing and presenting rewards may be a useful tool to both measure and improve welfare of animals. Important to note is the fact that this tool is based on the spontaneous behavioural response of animals and is therefore, in contrast to the nowadays mostly used invasive and stressful methods, a non-invasieve method to assess welfare. Furthermore, the results indicate that enrichment of the currently used poor housing conditions of laboratory rats (and probably also other animals) can serve to counteract stress (e.g. induced by experimental procedures) and, thus, may be a simple first step to take to improve animal welfare.
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