Walking behaviour of heavy and light broilers in an operant runway test with varying durations of feed deprivation and feed access.

Behaviour in general and locomotion in particular are influenced by physical abilities and environmental conditions in broilers. Little is known, however, about the motivation to perform behavioural activities in broilers. The distinction between motivation and ability is relevant as a lack of motivation has consequences for the interpretation of inactivity in broilers in terms of welfare. The aim of this study was to measure effects of varying motivation and physical ability on the distance broilers would walk for a food reward in an operant runway in limited time. Since body weight is recognised as an important aspect of physical ability, a high and a low body weight group were used to study the impact of physical ability. These two body weight groups were tested in an operant runway. Motivational aspects were manipulated by different feed deprivation durations before testing and by different feed access times during testing. With a similar duration of feed deprivation before testing and a similar feed access time during testing, birds with a low body weight walked a longer distance than birds with a high body weight. Distance walked in the runway was not influenced by age. Within a body weight group, birds walked a longer distance after a longer feed deprivation period before testing and walked a longer distance with shorter feed access time during testing. The latter effect was stronger in the low body weight group than in the high body weight group indicating a better physical ability. This experiment showed that distance walked was affected both by physical ability and motivation