Cattle or no cattle? Presence of cattleon pasture does not affect 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 shorter durations spent in Tonic Immobility (TI), a measure of fearfulness. Does duration spent in TI differ between broilers housed with or without young cattle on pasture? During two years, three batches of broilers (approx. 110-120 broilers each) were TI tested at four weeks of age and then allocated to control (only pasture) and treatment (pasture with ten cattle) balanced for seconds in TI. All broilers were kept for six weeks on pasture with or without cattle and were then TI tested again. TI tests were performed by one handler. Broilers were carried individually to the testing area, turned on their back and held with one hand over the head and one on the sternum for 10 s. The time until the broiler righted itself was measured as time in TI (max. 600 s). If a broiler righted itself earlier than 10 s after release, TI was not induced and the described process was repeated (max. 5 attempts). Number of attempts necessary to induce TI and duration in TI were compared between treatment and control group after six weeks on pasture. Due to the small number of replicates (at group level) we used descriptive statistics and visual inspection for interpretation. Duration in TI was lower in broilers ranging with cattle (mean ± sd 139 s ± 150 s) compared to broilers ranging with conspecifics only (150 s ± 146 s), but number of attempts did not differ (2 ± 1). Due to the small difference (10 s) found, we conclude that the presence of cattle did not influence the fearfulness measured by number of attempts and duration in TI.