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💡 Artificial Lighting and Livestock Welfare

Why Lighting Matters for Welfare

Light affects livestock welfare through multiple pathways: regulating circadian rhythms that control sleep-wake cycles, hormone production, and immune function; enabling visual orientation and social interaction; influencing reproductive physiology; and affecting behaviour and stress responses. Inappropriate lighting — too bright, too dim, wrong spectrum, or without adequate dark periods — causes welfare harm.

Species-Specific Lighting Needs

Cattle

Cattle respond strongly to photoperiod (day length). Long photoperiod (16 hours light) increases milk production through melatonin suppression and IGF-1 stimulation. Welfare considerations include:

• Minimum intensity: 150–200 lux at eye level for normal vision and behaviour
• Dark period: minimum 8 hours of low light (<50 lux) or darkness for normal circadian function
• Continuous 24-hour lighting impairs sleep and is a welfare concern
• Very dim light (<50 lux) continuously impairs normal visual behaviour and social interaction

Pigs

Pigs require adequate light for normal social behaviour and welfare:

• Legal minimum in the EU: 40 lux at pig level for minimum 8 hours per day
• Welfare recommendation: 100–200 lux during active periods
• Very low light promotes inactivity and may increase tail biting risk
• Complete darkness is used in some transportation systems to reduce aggression — this is a welfare compromise
• Provide dark areas in pens where pigs can sleep — pigs, like other animals, benefit from sleeping in reduced light

Poultry

Lighting in poultry production is extensively studied and regulated:

• Broilers: minimum 20 lux during active period; minimum 6 hours darkness (UK/EU requirement)
• Very low light (5 lux) throughout promoted inactivity in broilers — associated with increased metabolic disease
• Intermittent lighting (light-dark cycles within a day) can promote activity and reduce metabolic disease in broilers
• Laying hens: photoperiod controls egg production — 16 hours light standard; welfare concerns with 24-hour lighting (historically used)
• Spectrum: UV light exposure improves poultry welfare and behaviour; limited UV in standard LED systems is a welfare concern

Light Spectrum and Welfare

Many livestock species perceive ultraviolet (UV) light that humans cannot. Chickens in particular have four cone types (vs three in humans) and can see UV wavelengths. Standard LED lighting provides minimal UV, potentially impairing colour vision, social recognition, and foraging behaviour in poultry. Full-spectrum or UV-enhanced lighting is increasingly available and should be considered in poultry welfare improvements.

Circadian Disruption

Continuous lighting without adequate dark periods disrupts circadian rhythms across all species, causing:

• Impaired sleep quality
• Hormonal disruption (melatonin suppression)
• Immune dysfunction
• Behavioural abnormalities

All housed livestock should receive a regular period of reduced light or darkness equivalent to normal night duration.