by James Bailey
"ANC Consultant of the Year", 2000, 01, 02, 03, 04, 05, 06, 07

How does Photoperiod Work?
According to Geoffrey E. Dahl, assistant professor of animal and avian science at the University of Maryland, "exposure to light suppresses secretion of the hormone melatonin in cows as in other species. So, as the length of photoperiod increases, there is a reduced duration of high melatonin concentrations in the blood. The pattern of melatonin influences secretion of other hormones, particularly prolactin and insulin-like growth factor-I. Researchers believe that changes in IGF-I are important to the increase in milk yield observed in cows on long days."

Benefits of Long Day Lighting
There is a range in response when using long day lighting but the typical response is an increase of 5 pounds of milk per cow per day on both high and low producers! We have had several ANC customers start using long day lighting and have seen their average go up 4-5 pounds per cow per day. Usually it takes about 2-4 weeks to see a change relative to normal daily variation in milk production.

Experiments have shown no effect of long day lighting on milk lactose, protein, or solids. Slight differences have been seen in fat content, and in one experiment it increased and in another it decreased as a percentage.

Cows exposed to long day lighting situations will also consume more dry matter, but this is in response to higher milk production as they strive to meet the resulting increased demand for energy.

We would like to bring to your attention that it is not recommended to use long day lighting on your dry cows. According to Dahl, recent experiments have shown that dry cows on regular short day lighting periods "produced 7 pounds per day more when they freshened than cows exposed to long day lighting during their dry period." They suspect that the short days "reset" the cow's ability to respond to long day lighting in the next lactation.

Implementing Long Day Lighting
When implementing long day lighting on your dairy you need to make sure cows have exposure to 16-18 hours of continuous light along with a 6-8 hour period of darkness. If you place cows under 24 hours of continuous light you will gain no milk response. In 3x milking situations where cows are exposed to parlor lighting it can become more difficult to maintain 6 hours of uninterrupted darkness. This may call for the use of multiple lighting schedules within separate barns. The installation of timers to control the lights is recommended, since timers remove human error and keep the lighting schedule constant. Timers can also be set to turn lights off once full daylight intensities are reached, to help reduce electrical costs. According to Dahl "Dim red bulbs (about 4 watts) can be used to facilitate cow movement and observation during darkness because the red light has no effect on the cow's perception of darkness and, thus, melatonin secretion."

Responses to photoperiod are best at a light intensity of, at the very least, 10 foot candles at three feet from the floor in all areas where cows will be located. You should probably shoot for a target intensity of 15- 20 foot candles just to factor in problems such as dirt buildup which would block some of the light. In order to determine the light intensity of your barn or free stall you will need to use a light meter. Light meters can be obtained from an electrical supplier and most of our ANC consultants already have and use them! When installing lighting be sure to have all wiring and placement done in a proper manner by a professional to prevent any problems with stray voltage, inadequate lighting, etc.

When it comes to deciding what type of lights you should install you need to look at efficiency and the mounting height that would work best for your current facilities. The most common lights used are fluorescents, metal halide, and high-pressure sodium due to their energy efficiency. Dahl states that "in tie-stall and stanchion barns the relatively low ceilings allow use of fluorescent lights only (mounting height of 8-10 feet). In freestalls, lights can often be mounted at heights of 12-16 feet, so metal halide or high pressure sodium lamps are more appropriate."

Profitability
Even in times of low milk prices the use long day lighting is profitable. Typically, you can expect returns of about 30-40 cents per cow per day based on research data done at the University of Maryland. At a return of 34 cents per cow per day, a $69.95 investment in lighting (per cow) could be recovered in 206 days, about one fall/winter season. Keep in mind that this data was figured using an exsisting facilities and new construction costs could further reduce the required payback period.