Summary
This thesis explores how light intensity, spectral composition, and uniformity affect dairy cow physiology and behavior, finding that red light fails to constrict pupils (suggesting ipRGC involvement is necessary) and that non-uniform low-intensity red light reduces walking speed. While practical findings are specific to agricultural settings, the underlying photobiological principles—particularly around ipRGC stimulation and photoperiod-driven melatonin suppression—have broader relevance for circadian lighting design.
Key Findings
- Red light did not constrict the pupil in dairy cows, while blue and white light did, suggesting direct ipRGC stimulation is required for a steady-state pupillary light response.
- A 5-week study on 40 cows found no significant effect of light color (blue, red, or white) during a 16-hour daytime photoperiod on milk production.
- Plasma melatonin concentration was higher during dim night light than during daytime light across all spectral conditions, confirming photoperiod-driven melatonin suppression.
- Non-uniform, low-intensity red light caused cows to reduce walking speed in an obstacle course, highlighting the importance of light uniformity for visual comfort and safety.
- Field measurements on four Swedish dairy farms revealed that low-intensity and low-uniformity lighting was commonly used, suggesting widespread suboptimal light environments.
Categories
The Science of Light: Investigates spectral composition, intensity, and uniformity of light on physiological responses including pupillary light reflex and melatonin in dairy cows, with relevance to ipRGC stimulation.
Sleep & Circadian Health: Examines photoperiod manipulation (16h light/8h dark) and melatonin concentration responses to different light colors and intensities, relevant to circadian entrainment principles.
Author(s)
S Lindkvist
Related Publications
The Science of Light
- Phototransduction by retinal ganglion cells that set the circadian clock
- Color appearance models
- The mammalian circadian timing system: organization and coordination of central and peripheral clocks
- Diminished pupillary light reflex at high irradiances in melanopsin-knockout mice
- Melanopsin is required for non-image-forming photic responses in blind mice
Sleep & Circadian Health
- Phototransduction by retinal ganglion cells that set the circadian clock
- The mammalian circadian timing system: organization and coordination of central and peripheral clocks
- The two‐process model of sleep regulation: a reappraisal
- Melanopsin is required for non-image-forming photic responses in blind mice
- Strange vision: ganglion cells as circadian photoreceptors