The main findings of this study is that small broiler breeders at four weeks of age display a lower level of fearfulness accompanied with an increased level of social motivation. This is shown by small individuals displaying a shorter tonic immobility duration as well as a shorter latency to first head movement during the TI test, and performing more vocalizations and earlier vocalizations, both during a TI test and during an OF test.  Very few of the differences are found to persist to 18 weeks of age, although there are still indications that small individuals are less fearful than are large individuals during a TI test in every day fed animals.

The behavioural differences found between size groups are most pronounced  at 4 weeks of age, but to a lesser extent also persist to 18 weeks of age. No major differences were found between the feeding regimens. The  differences  found between small and large indviduals are not, however, indicative of small and large individuals adopting different coping styles. Such behavioural syndromes are characterized by more distinct and consistent differences in active avoidace behaviours and immobility behaviours across different behavioural tests than are found during this study.

The differences found, primarily those seen at 4 weeks, are still intriguing as it shows that smaller individuals are both less fearful and more socially motivated compared to large individuals. These differences suggest that small broiler breeders are less stressed and potentially better suited to cope with the high competition, multi-bird environment in which they are reared.    

For more details and figures, see subcatagories.