Behavioural aspects of feeding constraints: do broilers follow their gut feelings?

Abstract

Many trials investigating issues relating to the feeding and growth of broiler chickens do not include behavioural observations. One example is the work by Burkhart et al. [Behav. Gen. 13 (1983) 295]. They proposed that one of the associated changes in broiler chickens as a result of selection for lean, efficient growth is alterations to satiety mechanisms in the brain leading to excessive food intake and compulsive feeding behaviour. They compared fast and slow growing chickens with or without ventromedial hypothalamic (VHM) lesions, and found no changes in the fast growing strain, and increased fat deposition in the slow growing strain. However, no behavioural measures were examined, and a reduction in activity of the slow growing line as a result of the VHM lesions would offer an alternative explanation of the results. The present paper briefly outlines some of the vast body of research which has been carried out on different aspects of feed intake and growth of broilers in order to highlight the multitude of disciplines involved and factors at play. One reason for the paucity of trials which incorporate behavioural aspects of feeding may be, that the study of feeding behaviour in the broadest sense span two quite diverse scientific objectives: One is concerned with satiety and the mechanisms behind intake control. The other is concerned with daily feed intake, which is one crude measure of feeding behaviour, and the resulting growth and efficiency. However, feeding behaviour and other behavioural aspects of feeding often play an important role in the interpretation of production results. Conversely, many behavioural studies of growing animals, such as modern broilers, would benefit from a more stringent incorporation of nutritional data and discussions of non-behavioural aspects of growth. More studies of the interactions among physiological capacity, genetic potential, and social effects on feeding behaviour and activity of broilers would greatly improve our ability to interpret experimental results.