Growth heterogeneity has emerged as a welfare challenge in feed restricted broiler breeders, as it may indicate unequal resource acquisition. Size sorting and skip-a-day feeding regimes are tools to mitigate such development, however few studies have actually tried to quantify any within flock welfare differences. In the present study, this was investigated by characterising the stress coping ability of small and large broiler breeders through the concept of coping styles. A set of behavioural tests were carried out at 4 weeks of age as well in every-day fed and skip-a-day fed groups at 18 weeks of age. It was found that small individuals at 4 weeks of age vocalized more and sooner in an open-field test and a tonic-immobility test, showed shorter tonic-immobility duration and shorter latency to first head movement during tonic-immobility and displayed consistently higher levels of pen activity, compared to large birds. At 18 weeks of age small every-day fed individuals tended to show shorter tonic-immobility duration and shorter latency to first head movement during tonic-immobility compared to large every-day fed birds. The concern that small broiler breeders would experience lower levels of welfare due to differences in stress coping ability was not supported by this study. On the contrary small broiler breeders seem to display higher levels of sociality and lower levels of fearfulness at 4 weeks of age, and also lower levels of fearfulness at 18 weeks of age, possibly indicating that small individuals are better suited to cope with the challenges of broiler breeder rearing.
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Last updated: 05/19/15