Something new, upside down and on my back – Presence of cattle does not affect measures of fearfulness in broiler chickens

Summary

Keeping broiler chickens on pasture with cattle may increase range use of the chickens and reduce predation by predatory birds. Previous studies suggest that increased range use is associated with less fearfulness, as for example measured by a tonic immobility (TI) test, an inversion test or a novel object test.
During three years, four batches of broilers (110-120 broilers each) were TI tested at four weeks of age and then allocated to control (single species broiler group on pasture) and treatment (pasture with ten cattle) balanced for seconds in TI. The last batch of broilers was additionally tested for their reaction to three novel objects and a random sample (41 broilers) was tested for their initial reaction to a simulated predator (held upside-down/inverted by feet for a maximum of 30s) before and after pasture. After six weeks on pastures all broilers were TI tested again.
Descriptive statistics revealed: There was no difference between broilers ranging with cattle and broilers ranging only with conspecifics for duration in TI (treatment (mean ± sd): 129s ± 142s, control: 127s ± 136s) or in the reaction to a novel object. The intensity (wingbeats/s) in the inversion test was lower for both groups after pasture, but the delta between before and after pasture was greater for broilers with only conspecifics (1.6 ± 1.9) compared to broilers with cattle (0.8 ± 1.8). Fearfulness in broilers appeared in our study not to be affected by the presence of cattle on pasture.