Fear-related behaviour in Japanese quail divergently selected for body weight

Abstract

The damaging effects of fear on a number of performance indicators in poultry and other farm animals are becoming increasingly recognised. More specifically, there is growing evidence for a negative association between growth and fearfulness (an underlying behavioural characteristic). The present study examined this putative relationship in Japanese quail from two genetic lines that had been selected over several generations for low (LBW) or high (HBW) body weight at 4 weeks of age and in those of a non-selected control (CON) line. HBW quail were substantially heavier than LBW ones at 31 days of age (197 and 34 g, respectively), with CON birds occupying an intermediate (104 g) position. Birds were observed individually and once only between 26 and 32 days of age in one of three putative tests of fear. Quail of the LBW line showed greater avoidance of a conspicuous novel object placed near the home cage and longer tonic immobility fear reactions, and they vocalized and struggled later and less often during brief mechanical restraint than did the HBW quail. Quail of the control line generally showed intermediate responses. Plasma corticosterone concentrations following mechanical restraint were greater in LBW quail than in CON or HBW ones. Consideration of the intra-individual correlations between behavioural and adrenocortical responses to restraint suggested that the nature of the relationship was labile and that it was sensitive to the background genome. Collectively, the present findings demonstrated that underlying fearfulness was greater in quail that had been genetically selected for low rather than high body weight. The present results thereby support the hypothesis that fearfulness and growth are negatively associated.