When a Parkview Dairy in Delhi, Calif., completed a new dry cow and close-up facility in 2025, one design choice stood out: the barn is illuminated with red light at night. While unusual, the decision reflects a growing interest in how nighttime environments can influence cow physiology, particularly in the dry period when endocrine, immune and metabolic systems are under heavy transition stress.
The idea did not originate from a single study or trend. According to Dr. Vladimir Tadic, veterinarian with Azores Veterinary Practice who is familiar with the facility, the concept emerged from a broader awareness of circadian biology and a recognition that traditional barn lighting often overlooks how cows perceive light at night.
“You go to all these dairies, and it’s just regular white light, incandescent or LED,” Tadic explains. “We know about circadian rhythms, and just like with humans, cows are going to have a certain circadian rhythm. But we rarely talk about the influence that different wavelengths, creating different colors, could have on an animal, their healing and recovery processes, and their longevity.”
So the question stands: Why red light?
Circadian Rhythms, Melatonin and the Biological Night
Light exposure regulates circadian rhythm through the pineal gland. In darkness, cows produce melatonin, a hormone involved in signaling rest and regulating downstream processes such as stress response, immune function and metabolic balance. White and blue wavelengths can suppress melatonin production, even at relatively low intensities, potentially blunting the biological “night.”
“They’re trialing how red light impacts their dry cows and following them from dry all the way to close up, then into their next lactation,” Tadic says.
In this facility, red lighting (625 nm to 740 nm) is only used in the dry cow and close-up pens, not in the lactating barns. The red light is not meant to stimulate cows or increase production but as a way to avoid unnecessary circadian disruption during a critical recovery window.
“If the light exposure isn’t the right length of time or the right wavelength, it could be throwing things off reproductivewise or productionwise,” Tadic says. “If animals are less likely to rest, their milk yield is going to be lower.”
While this dairy is still collecting data on their lighting system, the biological rationale behind red lighting is consistent with known physiology. Potential advantages include:
- Preservation of melatonin secretion during nighttime, supporting normal circadian signaling
- Reduced stress hormone activation, as melatonin plays a role in moderating cortisol release
- Improved endocrine stability ahead of calving, which could support insulin sensitivity and calcium metabolism
- Immune system support, particularly important as cows prepare for the inflammatory demands of calving
- Enhanced rest and tissue recovery, including mammary tissue remodeling and rumen epithelial repair during the dry period
Recent work published in Frontiers in Veterinary Science adds some more context to the cattle lighting conversation. Researchers evaluated how different light spectra affected melatonin and physiological markers in lactating cows. Longer-wavelength light, particularly yellow (565 nm to 590 nm), was associated with higher melatonin levels and changes in immune and inflammatory indicators.
This work supports the idea that longer wavelength light might be beneficial for cattle at night.
A Management Tool, Not a Magic Fix
Cost, infrastructure and labor realities mean most dairies are unlikely to retrofit existing barns solely for light spectrum management. In the case of this dairy, the lighting choice was made during new construction, making implementation more feasible. Even then, they view it as one environmental component, not a replacement for sound nutrition, stocking density management or transition protocols.
“When you look at a dairy, different colored lighting isn’t really something that a lot of people consider, but I think it’s an important input that can change a lot of things for an operation,” Tadic says.
As research continues to evolve, lighting could prove to be one of the more overlooked variables in dry cow management.
