Dairy farmers: Long-day lighting a good investment


MADISON, Wis. –      Improving the lighting in dairy barns and regularly keeping the lights on during the shorter days of fall and winter is one of the most profitable investments a farmer can make-even better than milking three times a day, according to a dairy scientist.

“Using scheduled, supplemental lighting-also called ‘long-day lighting’ increases milk production and makes a safer working environment,” said Gunnar Josefsson.

Josefsson conducted an eight-week study last year on a dairy farm with about 350 cows.

“Annual profit can range from $62-$67 per cow. Pay-back time depends on the specifics of an operation, but six months to a year is a good average estimate, and takes into account increased feed costs,” he said.

How it works. Long-day lighting works by overriding a cow’s natural reaction to shorter days, which signal the approach of winter and a scarcity of food.

Josefsson explains that cows are naturally “programmed” to decrease milk production as day length decreases in order to save energy for essential needs such as maintaining body condition and providing for an unborn calf.

Cows on dairy farms, however, are well-fed year round, and do not need to decrease milk production to survive winter conditions.

Long-day lighting, typically 16 hours of light followed by eight hours of darkness, may reduce stress on cows and will make barns safer workplaces.

Sure bet. As investments go, Josefsson says that long-day lighting is a good one.

For a 200-cow barn, adding long-day lighting might cost $8,000-$10,000 but, with subsidies and financing from power suppliers, a farmer might have to pay only half that.

There are no additional labor costs, except occasionally cleaning the light fixtures, and each lamp should last six to seven years.

Electricity costs will increase somewhat, but new lamps are likely more efficient than existing fixtures.

Risk. Josefsson said that some farmers are concerned that long-day lighting will create problems with stray voltage, but he thinks improved barn lighting adds little or no such risk if installed correctly.

“Use 240-volt light fixtures and hire a licensed electrician who is familiar with farm installation and stray voltage prevention,” he said.

In addition, farmers can reduce both stray voltage and fire risks by replacing old wiring; power suppliers often offer cost-sharing programs for such renovations.

In order to start a long-day lighting program, farmers should install metal halide or fluorescent lamps in their barns and use them to supplement natural light, providing the cows 16-18 hours of light per day. Many free-stall barns get plenty of natural light, so farmers may turn the lights off during most of the daytime hours.

Farmers can use a formula, available from Josefsson or county extension agents, to calculate how much lighting they need, or they can consult a light equipment dealer.

Crucial aspect. Josefsson warns that it is crucial for farmers to turn the lights on and off at the same time each day, and suggests installing a timer to ensure consistency.

Achieving long-day lighting while milking three times a day may require some creative planning and staggered schedules for operating the barn lights.

Also, dust and droppings from flies and birds reduce light intensity substantially. Josefsson suggests cleaning the fixtures twice a year and checking the light levels with a meter.

Uninterrupted exposure to long-day lighting over the course of many months can lead to diminishing returns from milk production, so Josefsson recommends that farmers allow the cows to experience natural day length for some time each year, such as during their dry period.

This will reset the cows’ biological clocks. The cows will then respond to long-day lighting when they start to produce milk again.

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