Stereotyped behaviour in broiler breeders in relation to husbandry and opioid receptor blockade

Abstract

Restricted-fed immature broiler breeder hens housed in pens showed stereotyped oral activities directed towards drinkers and pen walls, whereas ad libitum-fed control birds did not. The restricted-fed birds also spent far less time resting than controls, and their spot-pecking (at walls) appeared to increase with age. Restricted-fed birds that were moved to three tiers of battery cages, after an outbreak of fighting, showed increased preening in the bottom tier, most spot pecking in the middle tier and most drinker directed activity in the top and bottom tiers. There was physiological evidence of stress associated with the fighting but not with food restriction per se. In a second experiment, treatment with nalmefene, an antagonist of central opioid peptide receptors, caused dose-related partial suppression of stereotyped pecking in another group of caged restricted-fed birds. It is suggested that central release of opioids during stereotyped behaviour may be both positively reinforcing and dearousing, and that such behaviour may represent a successful coping strategy for alleviating stress associated with restricted feeding.