The effect of loss of predictability and controllability of reward during frustration on behaviour in two strains of laying hens, Gallus gallus domesticus

In order to keep a high level of welfare an animal has to interact with the environment. Predictability and controllability of environmental stimuli seem to be of major importance. Loss of predictability and loss of controllability have a detrimental effect on animals. We hypothesised that both loss of predictability and loss of controllability would, among other behavioural effects of frustration, lead to an increase in the number of gakel-calls in laying hens. The gakel-call, expressed during the thwarting of behaviour, presumably is an indicator of frustration in laying hens. Predictability of reward was offered by a classical conditioning procedure, controllability of reward by operant conditioning. Assuming that controllability is predictability plus added control we also hypothesised that loss of controllability would lead to higher levels of gakel-calls than loss of predictability. Twenty hens of two commercial strains of laying hens, 10 ISA Brown Warrens and 10 ISA White Leghorns, were used. These strains of hens are known to differ in their reaction to frustration. They were subjected to frustration during a classical and an operant conditioning situation in a counterbalanced design. We found that in both conditioning situations the hens gave more gakel-calls in the frustration treatment than in the control treatment. No difference in levels of gakel-calls during frustration between classical and operant conditioning was found. Both loss of predictability and loss of controllability seem to impair a laying hen's welfare. The results suggest that the strains differ in behavioural strategy during frustration. When using the gakel-call as measure for welfare this difference in behavioural strategy should be taken into account.