Do broiler chicks have a cognitive representation of food quality?: Appetitive, behavioural and ingestive responses to a change in diet quality

Abstract

It has been observed that when a new diet formulation, or a new batch of the same diet formulation, is presented to poultry, there is a transitory suppression of feeding. It appears that the birds do not recognise the food as being edible, or classify it as being ‘unknown’. In order to understand more about food recognition and rejection, the aim of this experiment was to determine whether cognitive processes are involved. Sixteen groups of four broiler chicks were used, and were fed a low quality diet in their home pens. The groups of chicks were trained to run a winding maze to gain access to a high quality diet in a test trough for 15 min per day. When training was completed, the feed in the test trough for eight of the groups was changed to that which they received in the home pen, while the other eight groups received no change as a control. Time to traverse the runway did not show an immediate decrease on the day after the change ( P>0.05) as would be expected if the birds used a cognitive comparison to determine speed of approach to the test trough. However, the experimental groups were significantly slower compared to the control groups after 4 days ( P<0.05). The behaviour observed on the day of the change was indicative of frustration with more scratching and hurried movements shown ( P<0.05), and less pecking at feed ( P<0.01). Food consumption was lower for experimental groups compared to control groups on all days from the day of change onward ( P<0.001). It was concluded that although there was no definitive evidence for the presence of a cognitive representation of food, this may have been due in part to the testing of groups of birds rather than individuals, and the way in which food quality is perceived. The occurrence of behaviours indicative of frustration suggest that a cognitive expectation may have been present.