The effects of a light: dark cycle during incubation on white Leghorn layer chick development and behaviour

During incubation there are many external environmental variables that can affect chick development. Artificial light exposure could be a key factor underlying embryo-development, post-hatch performance and post-hatch behaviour. In-ovo light stimulation is known to impact the development of brain lateralisation and subsequent visual development throughout embryogenesis. Currently it is standard practice for industrial hatcheries to incubate eggs under complete darkness. The impacts of this photoperiod on chick welfare and development have not been fully considered to date. Here we investigated the effects of light during incubation on white leghorn layer chick behaviour, development and welfare. White leghorn chicken eggs were incubated in temperature controlled photoperiodic boxes under 16L:8D full spectrum white light (n=24) and under constant darkness (n=24; 0L:24D). After hatching, the chicks were split into 8 pens across 2 experimental rooms. Chick body weight (g) was taken at hatching, and then weekly until cull at 4 weeks of age. Chick behaviour was analysed using BORIS behavioural analysis software. Body mass data was analysed with analysis of variance (ANOVA) using statistical software program R version 4.3.1. Chicks incubated under 16L:8D had significantly higher body weight than those incubated in darkness. Chicks incubated in 0L:24D achieved a similar growth rate to those incubated under 16L:8D at week 2, but by week 4 the effect of light treatment on body weight manifested again. Phenotypic changes can be influenced by the environment through epigenetic effects and light can alter metabolic and physiologic characteristics. Further analysis is underway to examine the effects of light during incubation on the time and length of the hatching window, chick behaviour, the neuroendocrine system as well as cage enrichment usage.
Funded by the BBSRC (SLM) and The Animal Welfare Foundation (LJH & SLM). LK is supported by an EASTBIO DTP. All work was performed under ARRIVE guidelines and ethical review.