How to get the most out of long-day lighting

Andreas milking parlor

Long-day lighting has been around on many farms for years.

Most of the time it works, but after reading a few recent research studies and walking through multiple barns, the question came up of how much maintenance do lights require and when does electric cost outweigh the benefits.


Over 20 years ago, research proved that long-day lighting would positively benefit milk production by almost 10 percent.

Since then, many producers retrofitted their barns for long-day lighting, which improved milk production and decreased worker injuries.

Many things have changed since then, such as better light design that actually has full output on a cold day, 20-year-old lights that are not all working, and most importantly, milking more hours per day.

Brighter lights

A study from Wisconsin recommends cleaning lights twice a year in a long-day lighting system so that lights do not become dim from dust and fly specks — which we all know rarely happens with everything we have going on.

Who has time to climb up and clean each light in the barn? With this in mind, when are we wasting electricity with our long-day lighting being too dim?

The recommendation is to have 15 foot-candles or greater of light everywhere in the barn.

Some studies have found a response down to 10 foot-candles, but the recommendation is to start at 20 foot-candles when installing a new system.

Unfortunately, from the time we replace and install new lights, they only get weaker, either by collecting dust and fly specks or the design of most lights that dim over time.


The other problem found in long-day lighting studies from New York and Michigan, designed to look at LED lights versus florescent lights, was lack of milk performance enhancement from either type.

This brought up a question often asked by a 4-year-old, why?

Further investigation discovered that a few other fundamentals were missing. They are probably missing on my home farm and yours, if you milk three times a day.

Long-day lighting is effective when 16-18 hours of light follows 6-8 hours of uninterrupted darkness. What happens on many farms is that one shift of milking is during the dark period.

When the cows walk into the parlor’s full light, out the window goes the long-day lighting advantage. Since then, follow up studies have looked at making long-day lighting work on these farms.

Lighting zones

Separating the milking barn into lighting zones controlled separately can allow for 6 hours of darkness in at least part of the groups.

Studies have found that, when possible, at least the fresh cows should experience proper long-day lighting. In areas of the barn where workers still need to move cows without affecting those on long-day lighting after the lights shut off, red lights or dim lighting below 5 foot-candles should be used.

Cows do not sense this level of lighting as daylight, but workers can still see enough to move.

Short days

Another part of effective long-day lighting is allowing the cows to experience short days during the dry period.

Short days can be hard to achieve since the ideal short day is 8 hours of light followed by 16 hours of dark.

When short days are achieved, production can increase by 6.8 pounds per day along with an increase in fat and protein in the following lactation.

While you might not be able to achieve true short days, using artificial lighting for less than 16 hours per day will help improve the outcome of long-day lighting.


Many operations are looking at upgrading their barn lights to LED’s to save on electric cost. There are many factors to consider when upgrading your barn.

The first is making sure your barn lighting is adequate. For about $100, a light meter can be purchased to check the light and shadows in your barn at a height of 3 feet in the freestalls and 5 feet in the alleys.

LEDs have many designs, including special fixtures, Edison base screw-in lamps, and 4-foot-tube lamps that fit in modified fluorescent fixtures.

Remember when replacing older lights with LEDs that the important part is not the watts or energy usage, but rather the lumens, or light output.

LEDs tend to come in color variations of white to blue, with blue being preferred for dairy operations.

These lights cost twice as much to install but will last twice as long with three quarters the operational cost of fluorescent lights.


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