ABSTRACT
Broiler breeder chickens show apparently abnormal behaviours when subjected to routine quantitative food restriction during rearing. By using a combination of videorecording and radiotelemetry, this experiment addressed the question of whether such behaviours are associated with de-arousal. In each of 2 years, 3 female chickens had radiotelemetry devices (Data Sciences) implanted surgically at 12 weeks of age, for measuring putative physiological indices of arousal (heart rate, blood pressure, body temperature, telencephalic EEG). Subsequently, when caged individually and moving freely, they were monitored over 2 days when their daily food ration (60 g pellets provided at 0900 h) was all eaten in <10 min. Their behaviour (nine categories) and arousal indices were recorded in every minute during the photoperiod (0700 to 1900 h), using special computer software for videorecording (Noldus) and radiotelemetry (Dataquest LabPRO) analyses. Most time was spent in behaviour categories stand, push bar and feeder directed. Heart rate, blood pressure, body temperature, and relative powers in delta (1-4 Hz) and theta (4-8 Hz) frequency bands of the EEG power spectrum were all highest during feeder directed, whereas heart rate, temperature and delta EEG were all lowest during stand. Judging from significant correlation coefficients between times spent in different behaviours and corresponding physiological variables, across the day, and between ranked mean values of the 6 birds, other trends were also evident. For example, total time spent in all (non-food directed) oral behaviours was related positively to an index of de-arousal (slow wave EEG) and negatively to an index of arousal (heart rate). Collectively, however, these results provide apparently conflicting evidence of both arousal and de-arousal being associated with every behaviour analysed. This conclusion is explicable if abnormal behaviours are related to arousal in a homeostatic way [Savory, C.J., Kostal, L. Temporal patterning of oral stereotypies in restricted-fed fowls: 1. Investigations with a single daily meal. Int. J. Comp. Psychol. 1996, 9:117-139.], being both stimulated by it and reducing it.
