July 26, 2001

Make Milk with the Right Amount of Light

Keeping barn lights on a timer may increase dairy cows’ milk production by 8 to 10 percent, according to a North Dakota State University dairy specialist.

Manipulating photoperiod (the ratio of light to darkness) can increase milk production of your cows by altering the hormone melatonin, according to J. W. Schroeder of the NDSU Extension Service.

Melatonin increases when the barn becomes dark. Increasing the photoperiod decreases melatonin and increases the hormone insulin-like growth factor (IGF-1), which prompts an increase in milk production.

"What you should expect to see is a gradual increase in milk yield of 8 to 10 percent, no changes in milk protein percent or somatic cell count, and a very slight decrease in milk fat percent. This should occur within one month of starting the lighting program along with a gradual increase in feed consumption," Schroeder says.

The concept of manipulating photoperiod has been around for some time. Recent research at the University of Maryland further documents this procedure. So how do you go about it?

Keep lights on a timer. Cows must have between 6 and 8 hours of darkness and 16 to 18 hours of light. Illumination must be 20 footcandles per 50 feet of barn length. To calculate the number of fixtures needed for your facility, use the following equations.

width of barn x length of barn = barn area in square feet

barn area x footcandles needed x outdoor lighting constant = lumens needed

(outdoor constant = 3 for a barn with curtains, 2 for a tiestall barn)

lumens needed ÷ wattage per lamp

(250 watt lamp = 20,500 lumens; 150 watt lamp = 14,000 lumens; 400 watt lamp = 36,000 lumens)

For example, in a 112 foot long by 56 foot wide barn, the area is 6,272 square feet. (56 feet x 112 feet = 6,272 square feet) The number of lumens needed for this freestall barn with curtains is 376,320. (6,272 sq. ft. x 20 footcandles/50 ft. of barn length x 3 outdoor constant = 376,320)

The number of 250 watt fixtures needed is 18. (376,200 ÷ 20,500 lumens = 18 fixtures)

"Typically, it’s not too difficult to manipulate the photoperiod," Schroeder says. "The main guideline is to keep lights on for 16 to 18 hours by using a timer. For herds that are milked three times a day, achieving the required hours of darkness may be a bit more difficult. However, dim red lights like those used on scoreboards can be used. It appears that these lights, which can be purchased at large hardware stores, do not suppress melatonin."

Schroeder notes that research results indicate that when BST is administered to herds to boost milk production, manipulating photoperiod will still give an 8 to 10 percent boost to milk production.

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Source: J.W. Schroeder, (701) 231-7663, jschroed@ndsuext.nodak.edu
Editor: Tom Jirik, (701) 231-9629, tjirik@ndsuext.nodak.edu