The effects of light during incubation and a post-hatch enrichment on white Leghorn layer chick development and behaviour

Light exposure during artificial poultry egg incubation could be a key element underlying embryo development, post-hatch performance and post-hatch behaviour. While previous research has primarily focused on mitigating negative effects, the influence of light during incubation in relation to positive animal welfare indicators and interaction with enrichment has received less attention. Here, we investigated the effect of light during incubation and an environmental enrichment on body mass and chick behavioural responses. We quantified behavioural time budgets and activity levels, environmental usage and interactions with the enrichment of a dark shelter. White Leghorn chicken eggs were incubated in temperature controlled photoperiodic boxes under either constant full spectrum white light (24L:0D) or darkness (0L:24D). The chicks were split into 8 pens across 2 experimental rooms post-hatch, and two pens per room contained a dark shelter. Results indicate that at 4 weeks old, chicks incubated under light were heavier compared to those incubated under darkness (p<0.05). The dark shelter enrichment did not have an effect on chick body mass development. Light during incubation had no effect on behavioural time budgets and activity levels, but the presence of the dark sheltersignificantly lowered foraging (p=0.01), decreased eating (p=0.01) and increased resting (p<0.001) behaviour. Together these results suggest that light during incubation can affect chick growth rates and this might be a consequence of alternated metabolic and physiologic processes. Data on the dark shelter showed that light during incubation does not influence how chicks would interact with the enrichment. However, chicks use this enrichment resulting in lower activity levels overall. These findings have the potential to synchronize behavioural patterns and therefore mitigate behavioural problems like feather pecking. The implementation of adequate light:dark cycles into commercial practice is not a huge cost, but it could have tremendous impact on the welfare of billions of chicks. Further research into the effects of environmental conditions in early life could improve chick health as well as enhance laying hen welfare in later life.