Circadian Rhythm in Cattle: Why Lighting Strategy Now Drives Productivity

In modern dairy farming, lighting is too often seen as a passive utility. In reality, it's a powerful tool - directly influencing biological performance, animal well-being, and operational outcomes.

At the center of this influence lies the circadian rhythm: the internal clock that governs cows' metabolic, hormonal, and behavioral cycles.

What is Circadian rhythm and why does It matter? 

The circadian rhythm is a 24-hour internal timing system regulated by light-sensitive neurons in the brain. In cows, this system governs:

• Melatonin production: Darkness activates melatonin, promoting rest. Light suppresses it, keeping cows alert and active.
• Hormonal regulation: Stable circadian patterns support lactation hormones (e.g., prolactin), reproductive cycles, and growth factors.
• Immunity and stress response: Well-aligned rhythms enhance immune competence and reduce cortisol-driven stress.

Disrupted light cycles, such as 24-hour lighting or poor spectral quality, can impair feed conversion, fertility, and milk yield.

The business case for circadian-aligned lighting

Dairy research shows that extending photoperiods to 16–18 hours of daylight, followed by 6–8 hours of darkness, can increase milk yield by 3–7%.

This happens through:

• Increased feeding time and metabolic efficiency
• Improved milk hormone expression
• Reduced rest and disruption stress

However, these gains only materialise when light quality, spectrum, consistency, and biological timing are optimised - not simply when brightness increases.

Designing lighting systems for biological needs

A high-impact lighting system includes several core components:

Photoperiod management: Milking cows benefit from a Long Day Photoperiod (LDPP), which means 16–18 hours of light and 6–8 hours of full darkness.

In contrast, dry cows respond better to a Short Day Photoperiod (SDPP), typically 6–8 hours of light and 16–18 hours of darkness. An effective lighting climate for lactating cows includes an automated regime delivering 16–18 hours of 200 lux per m², followed by a consistent dark phase.

Light spectrum: Specific lighting spectrums, used in combination with correct intensity, uniformity, and scheduling, have been shown to support higher milk yields.

Under the RUDAX concept from HATO, the Lactivus Technology spectrum is tailored for dairy cows - suppressing melatonin and stimulating IGF-1 (Insulin-like Growth Factor 1). This keeps cows active longer, helping to sustain high milk output over extended periods.

Consistency and Predictability: Like humans, cows benefit from a predictable environment. A lighting system that delivers consistency allows cows to anticipate feeding, resting, and activity times - reinforcing biological rhythms that directly support milk production. Routine and predictability are key in balancing stimulation and rest.

Light as a Biological Input 

Lighting is a biological input with direct improvements in milk volume, feed efficiency, animal comfort, and carbon performance. When aligned with cows’ circadian rhythm, light becomes a productivity lever, not just an expense.

For any forward-looking dairy operation, upgrading to biologically intelligent lighting is one of the lowest-barriers to higher-returns.