When cows are exposed to long days, 16 to 18 hours, research has shown they will give 4 to 5 pounds more milk per day. Long days can be created by exposing the cows to artificial or a combination of natural and artificial light.

In a tie-stall barn that can be accomplished by installing a row of light-emitting diode tubes, T-8 or T-5 fluorescent fixtures, over the feed alley. In a free-stall barn, light-emitting diode, metal halide or high-pressure sodium lamps are normally used unless the ceiling height is less than 10 feet. Then light-emitting diode or high-output T-8 fluorescent fixtures would likely be recommended.

Long-day lighting will generally not work for farms milking three times per day because it’s nearly impossible to achieve six to eight hours of darkness due to milking schedules. It might be possible to achieve for a select number of groups but likely not the entire herd.

Most dairy barns are too dark. Improving barn lights and operating them according to a specific schedule can improve both the profitability and working conditions on a dairy farm. That technique is known as long-day lighting or photoperiod control. It has been well researched in the past 20 years.

Benefits are many.

  • increased milk production
  • improved heifer growth
  • more enjoyable
  • safer working conditions

Investment creates profit

Studies have shown that exposing cows to supplemental light during the short days of fall and winter can increase milk production by about 5 percent to 16 percent. But cows also eat more, and there’s a cost to install and operate the lights. The increased milk yield pays for the extra feed and the cost of the lights – and still leaves a net profit. Estimated investment costs and pay-back periods for lights in a 40-cow tie-stall barn range from $1,672 paid back in 111 days to $2,125 paid back in 332 days

Create 16-18 hours light, 6-8 hours dark

Most of the experiments with long-day lighting have provided supplemental light, extending the fall and winter days in September through March or April – creating 16 to 18 hours of light per day. The effects of the technique are well-documented. A producer can expect a substantial production increase by using a consistent program of 16 to 18 hours of light followed by six to eight hours of darkness. Note that consistent night-off and early morning-on timing is necessary to achieve an increase in milk production.

Workplace safer, more productive

Trivial accidents such as slips and falls happen during barn chores. They may be disabling and are occasionally fatal. Good lighting helps workers spot obstructions and slippery areas. Better lighting also makes it easier to notice cows in heat, cows with health problems, cows off feed, poor feed quality, etc. In addition most people appreciate a well-lit workplace and consequently may become more productive.

Improve lighting in stall barns

Cows are stimulated to produce more milk when they register longer days through their eyes and brain. The average light intensity in the barn needs to be at least 15 foot-candles at cow-eye level. That can be achieved by installing sealed fluorescent-light fixtures over the manger. Avoid using incandescent lamps because they are not energy-efficient and have a short bulb life. In most stall barns natural daylight is insufficient. Therefore the manger lights need to also be on during the day. To ensure consistent light and dark periods, a timer should be installed.

Improve lighting in

free-stall barns

To stimulate milk production, provide an average of 15 or more foot-candles in all areas where cows spend time. Be sure to provide sufficient light also to outside free-stall rows. Certain work areas such as treatment, breeding and feeding require 20 or more foot-candles. Metal-halide and high-pressure sodium lamps provide good light output and have a long lamp life. Both represent energy-efficient options for free-stall barns.

The amount of natural light in non-insulated, naturally ventilated free-stall barns during daytime typically exceeds 20 foot-candles. Thus the lights can normally be turned off for most of the day and operated only during early-morning, late-afternoon and evening hours. Install a timer to achieve consistent on-off times. A photo sensor should be installed to save energy during normal days, but automatically keep the lights on during exceptionally dark winter days.

Appropriate for most dairy operations

Long-day lighting is profitable and feasible for stall barns and free-stall barns of all sizes. Farmers should take advantage of the opportunity to improve profitability and working conditions. A simple light meter can tell whether the amount of light in a stall barn is too dim. Measuring light levels after the installation can verify that new lights deliver light levels required to stimulate milk production. Area utility-company representatives and county agents may be able to assist with measuring light levels – or provide a light meter on a loan basis. Otherwise a simple light meter can be purchased for $100 to $150.

This material was developed by the Wisconsin Healthy Farmers, Healthy Profits Project, whose goal is to find and share work-efficiency tips that maintain farmer health and safety, and also increase profits. Visit bse.wisc.edu or call 608-262-7408 for more information.