Artificial Lighting and Livestock Welfare
Artificial lighting in livestock housing affects both production and welfare through circadian rhythm regulation, behaviour, and hormonal systems. Understanding the welfare implications of different lighting programmes enables management decisions that support both productivity and animal wellbeing.
Lighting and Circadian Rhythms
Animals have endogenous circadian clocks that synchronise physiological processes to the daily light-dark cycle. Disruption of these rhythms — by constant light, completely light-free environments, or irregular lighting schedules — causes physiological stress, disrupts sleep, alters hormone secretion, and impairs welfare. Livestock welfare standards increasingly specify not just minimum lighting intensity but also lighting duration and dark periods.
Dairy Cow Lighting
Long-day lighting programmes (16-18 hours light, 150-200 lux minimum) increase milk yield by approximately 8-10% in dairy cows through melatonin suppression and IGF-1 stimulation. This is one of the most consistently evidence-based lighting interventions in agriculture. Providing 6-8 hours of continuous darkness maintains circadian rhythm integrity and is compatible with the welfare and production benefits of long-day lighting.
Night lighting that enables adequate observation and monitoring without disrupting dark periods uses lower-intensity lighting during dark hours while maintaining safety for stockpeople.
Poultry Lighting
Broiler lighting programmes require careful welfare consideration. Constant bright lighting was historically used to maximise feeding and growth but is associated with leg problems, eye disorders, and reduced rest. EU welfare regulations now mandate minimum 6-hour dark periods. Dim light during the dark period rather than complete darkness improves bird safety while maintaining circadian function.
Laying hen lighting programmes manipulate photoperiod to control sexual maturity timing and maintain laying throughout the year. The step-up lighting programme — gradually increasing day length — mimics natural spring lengthening and is compatible with hen circadian welfare.
Pig Lighting
Pigs require minimum 40 lux for 8 hours daily under EU welfare standards. Higher lighting levels (>100 lux) are associated with increased activity and reduced stereotypy in sows. Continuous artificial darkness impairs welfare through disruption of circadian rhythms and reduced opportunity for normal daily behaviour patterns. Natural light (through windows or roof lights) provides preferred spectrum and circadian cues.