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1309 PD: Make money and save energy with dim night light

Gunnar Josefsson Published on 25 August 2009

Night light isn't just for your kid's bedroom. Dim light in your dairy barn may benefit your cows and improve your bottom line. It offers a solution to the dilemma for farmers milking 3X and wanting to use long day lighting, i.e. providing darkness for cows or light for workers during the night.

The amazing eye
At the high end of our eyes' operating range, full sunlight at noon on a clear summer day measures about 10,000 foot candles. A full moon on a clear night provides only 0.03-0.05 foot candles. Thus, full sun light is a staggering 200,000 to 300,000 times more intense than is light from a full moon. The human eye, as well as the cow eye, is an extremely adaptable biological instrument able to function in blazing sun or near darkness. This adaptability of the human eye makes dim light surprisingly usable for night time work, if the light is of sufficient high quality.



Why consider dim light?
Many dairy farmers use some light at night, allowing unobtrusive night inspection without the need to turn on the full light in the barn. Providing cows with basic lighting may also help them feel safer and remain more calm during the night. In fact, some European countries require that dairy farmers provide night light to meet animal welfare regulations. In Sweden, e.g., a light level of at least 5 lux (0.5 foot candles) is required in dairy barns at night.

Farmers interested in practicing long day lighting (LDL) have other reasons to consider using dim night light. Herds milking 2X are usually able to provide both the daily required 16 to 18 hours of bright light and the recommended 6 to 8 hours of uninterrupted darkness for lactating cows. After having completed their lactation on LDL, the dry cows need a break from the long days in order to be able to respond to LDL again, after freshening. The easiest way to organize this is to allow the dry cows to experience natural day length. Ideally, no artificial light should be used for dry cows. Depending on work routines and the season, artificial light might be needed for work in the dry cow barn. Using dim light at a level that is perceived as "dark" by cows can provide light needed for basic work, while allowing cows to continue experiencing naturally short day length.

Many dairy farmers with 3X milking have decided not to practice LDL. They concluded that they were obliged to choose their employees' need for night light over their cows' need for darkness (if using LDL) -- and use full light in the barn all night.

Research sheds light on the subject
Professor Alma Kennedy, University of Manitoba, is the authority on the effects of night light on cattle. Her research demonstrated that a level of 5 foot candles (1/3 of what is recommended when practicing LDL) had a considerable impact on the endocrine functions at night. This relatively low light level reduced the production of melatonin (the normal "darkness" hormone) by 50 to 75 percent. At the lower light levels of 0.5 and 1.0 foot candles, there was no such interference -- the production of melatonin remained the same as during absolute darkness (0.0 foot candles). The intermediate light intensities between 1 and 5 foot candles have not yet been studied. Based on these findings, Kennedy concluded that night light at levels up to about 1 to 1.5 foot candles can be used for night time work, without disturbing the endocrine balance of cows exposed to LDL.

Some farmers have installed red light for night time barn work, with the understanding that red light is perceived as "dark" by cows on LDL. Many farmers were not satisfied with the quantity and quality of this lighting for work purposes and returned to using full light all night long -- and stopped practicing LDL.


The dim white night light we describe here (about 1 foot candle) provides a far superior quality and quantity of light than red night light.

A word of caution is in order regarding the assumption that cows don't react to red light as "light." A study was carried out with a group of steers, provided true red (monochromatic) light at a somewhat increased light intensity, compared to the red light documented not to interfere with the production of melatonin -- the dominant darkness/night hormone. This study demonstrated that the animals did react to that level of red light as "light". Thus, increasing the level of red light in order to achieve better lighting for work is not an option -- since it would jeopardize the effectiveness of LDL.

On-farm experimentation and experiences
When considering the impact of dim light on cows, we can draw conclusions based on university research studies. But what can dim light do for employees working in the barn at night? Would dim light, at a level acceptable to cows on LDL, provide suitable work lighting? No formal studies are available to address this question.

Knowing that cows can tolerate white dim light at a level 20 to 30 times brighter than good moonlight, this issue was worth investigating further. In 2005, I collaborated with a commercial dairy (Majestic Meadows in Wisconsin), testing a dim light system providing an average of 1.3 foot candles. The owners found this light level acceptable for basic barn work at night. I have since designed numerous lighting systems for LDL on 3X dairies. The consistent feedback from farmers is that they are satisfied with the dim night light and surprised that workers are able to identify cows at a distance with this low level of light.

Is dim light profitable?
Using dim light can be a money-maker by allowing dairymen to combine two profitable herd management practices; i.e. 3X milking and LDL. Dairies approaching a 24/7 parlor schedule (whether 3X or 2X) are now able to take advantage of the full economic benefits of LDL -- about $100 net profit per lactating cow per year.

Dim night light can also be a money-saver. This new way of practicing LDL is based on light fixtures operating on low power to provide dim light for 6 to 8 hours per night. This can save 30 to 40 percent of the energy cost for operating light fixtures, compared to operating the same number of fixtures at full power all night long.


-- If you milk your cows 3X, or otherwise approach a 24/7 parlor schedule -- consider adding LDL to your box of profit tools. LDL is quite profitable also with unfavorable milk and feed prices and made possible by using dim light!

--For your new or improved barn lighting -- shop for a whole system solution rather than focusing only on fixtures. Ask potential vendors for a lighting plan that meets the lighting needs for all categories of cattle (lactating, dry and heifers) and accommodates your herd management routines and facilities.

-- Take advantage of rebates or other incentives offered by your utility or state energy conservation organization. In some areas, incentives for the most energy-efficient fixtures are as high as $90 per fixture.

-- Today's fluorescent fixtures represent modern, highly energy-efficient lighting technology. Be sure to choose fixtures suitable for the harsh environments in dairy barns and parlors; fully sealed and gasketed and approved for damp or wet locations. PD

Gunnar Josefsson
Dairy Consultant