The effect of brooders on the synchronization of behaviour in broilers

Abstract: For the first weeks of their life chickens in nature sleep and rest on the ground under the brooding hen. However, broilers in conventional production are kept in very barren environment with high stocking densities which does not encourage sleep and rest. It has been hypothesized that the absence of a broody hen leads to the chickens being less synchronized in their behaviour and that this increases the risk of resting chicks being disturbed by other active chicks. The aim of this study was to investigate if access to brooders would influence synchronization of behaviour and, because of potentially better sleep, make the chickens less fearful and have a more lasting memory. 600 broilers of the fast-growing genetic line Ross 308 were raised in 10 floor pens with 60 birds in each pen. There were four pens with heated brooders (HB), three pens with cold brooders (CB) and three pens without brooders (C). The chickens behaviour was recorded in the home pens on 7 and 21 days of age to measure their synchronization. Fourteen chickens from each treatment were subjected to a reversal learning test at 2 weeks of age and at 9 and 19 days of age five chickens from each pen were put through a tonic immobility test. At 7 days of age chickens from the HB and CB groups were more synchronized in their comfort behaviours and the HB groups also had a tendency to be more synchronized in their standing behaviour. At 21 days of age chickens from the HB groups were more synchronized in their resting behaviour. However, chickens from the CB and C groups were more synchronized in their explorative behaviour. In the reversal learning test chickens from the CB groups made more right choices and less wrong choices compared to the other groups. There were no differences found between the treatments in the tonic immobility test. The results from this study indicate that access to heated brooders for the first three weeks of life made the chickens more synchronized in their resting behaviour. However, more synchronized resting was not found to have an effect on their fearfulness nor on their performance in a reversal learning test. Further research would be needed to evaluate what effect access to heated brooders, and what effect synchronization, has on sleep disturbances.