Why is providing adequate lighting important for meat chicken welfare?

In commercial systems, most meat chickens are housed in large sheds with artificial lighting. Unless these sheds provide access to an outdoor area or have curtained rather than solid sides, most birds will not have access to natural light.  

Meat chickens housed under commercial conditions are subject to artificial lighting schedules. These schedules often employ long daylengths with much shorter periods of darkness than those experienced during natural day and night cycles. Some farms will keep birds in long periods of bright light to encourage them to keep eating. Sometimes, coloured lighting (e.g. red or blue lighting) is used, known to be a cause of increased fearfulness or reduced activity levels in birds.

Chickens require a certain amount of light to encourage normal behaviours and improve health. Meat chickens, like other animals, use the external light-dark cycle to establish their circadian rhythm, which in turn regulates bodily processes and is an important determinant of behaviour, physiology and immune function. In the absence of natural light, artificial light needs to be provided at an appropriate intensity and duration. Meat chickens require adequate sleep for good health and welfare. Periods of darkness that encourage birds to rest are therefore essential.  

Providing meat chickens with short dark periods (e.g. 1 hour or 4 hours) has been found to result in poorer growth, poorer feed conversion efficiency, poorer leg health, poorer eye health, higher mortality, an absent or minimal circadian rhythm, reduced activity levels and a reduced behavioural repertoire compared to birds provided with longer dark periods. 

Light intensity (measured in lux) can be used to manage the activity levels of meat chickens, with higher light intensities associated with higher levels of activity. Higher levels of activity have benefits for bird health and behaviour such as improved leg health, reduced mortality, increased comfort and foraging behaviours. Conversely, low light intensity is associated with increased lameness, footpad and hock burn, and breast blisters. 

Light intensity in the shed can be varied to help improve bird welfare. Meat chickens prefer brighter lit areas in the shed for activity (including feeding and foraging) and darker areas for resting or sleeping. While there is generally some variation in light intensity across the shed floor (e.g. light coming through curtained sides, openings to a range, fans, and air vents), the aim has traditionally been to keep lighting uniform with the main purpose of encouraging birds to eat.

When meat chickens have access to natural light, they are generally more active, increase their behavioural repertoire (e.g. exploring, feeding, drinking, preening), and have improved foot and leg health. Natural light adds to environmental complexity, creating variety within the environment, further enhancing bird welfare. Natural light is brighter than artificial light and there is increased variation in intensity throughout the day which may explain the positive effects on bird welfare. Natural light also contains ultraviolet (UV) radiation which has been found to reduce stress and fearfulness in birds, decrease lameness, reduce mortality, and improve growth.

Birds provided with an outdoor area will have access to natural light for at least part of the day. However, whichever system they are housed in, most meat chickens will still spend most of their time indoors. Improving access to natural light in indoor climate-controlled sheds in Australia is not straightforward. To be successful will require innovative shed design and placement of light openings to maintain optimal shed conditions including temperature and humidity.