Timidity in Japanese quail: effects of vitamin C and divergent selection for adrenocortical response

Male Japanese quail chicks of two genetic lines selected for low (LS) or high (HS) adrenocortical responses to mechanical restraint were housed in mixed-line groups of 24 in four compartments of a multitier brooder battery at 20 days of age. Quail in two of the four compartments were given vitamin C (ascorbyl-2-polyphosphate, APP, 1 g L-ascorbic acid/L) solution for 48 h, whereas the other birds received untreated tap water as usual before they were tested at 23 days of age. At test, each quail was placed individually in a dark, sheltered compartment of an emergence box and allowed 1 min to acclimatise before a door was raised allowing access to an illuminated and exposed area. Vocalisation and the latencies to head and full emergence were then recorded to measure its fear levels. More LS quail vocalised than did HS ones. They also emerged more rapidly from the sheltered compartment into the illuminated one than HS birds. These findings further support our hypothesis that decreased fearfulness has accompanied genetic selection for reduced adrenocortical responsiveness. Treatment with APP reduced the latency to emerge fully into the exposed compartment, and there were no line x treatment interactions. These results suggest that vitamin C supplementation alleviated fearfulness, regardless of existing line differences in this behavioural trait.