The Basics of Light Management for Egg Layers

Eric Gingerich DVM
Diamond V


Light is used to control the sexual maturity of the egg layer and to allow normal behaviors such as eating, drinking, foraging, etc. Birds detect differences in day length by penetration of light waves through the skull to photoreceptors in the pineal gland and hypothalamus of the brain. This is where hormonal and behavioral control occurs to control the birds’ circadian rhythm and reproductive function.

A light clock will be needed that can increase time in 15 minute increments. Incandescent, florescent, or LED lights can be used as long as their temperature rating is 2700 K. The wattage of the bulb will be determined by the reflection off the walls and the height of the bulb from the birds. As a rule of thumb, one should be able to read a newspaper easily at the level of the feed trough.

Light Management

Light in Chicken House

Layers are quite sensitive to the effects of light. My mother had 30 DEKALB Brown hens in Indiana in an old hog house. She got them at point-of-lay in May from a local grower. The flock was doing great and producing at 100% until August 1st. All of a sudden, production dropped to near zero. She called her son the vet. I asked if she had been giving them light. No was her answer. The decrease in day length from the longest day on June 22 to August 1 had caused a de-stimulation of the birds’ ovaries. A quick trip to the hardware store for a light clock set at 16 hours, a light fixture, and a 40-watt bulb did the trick.


The rule of thumb is to never increase day length during the grow period in order to not stimulate the bird into production before the pullet is ready for egg laying.

Young chicks are started off with long day lengths for the first 3 weeks to allow sufficient time for eating. Normally, a 22-hour day is given the first week, 18 hours the second, and 16 hours the third.

At 3 weeks of age, the daylength will be constant until the body weight for stimulation is reached. The day length used is dependent upon the housing used. If the housing is light-tight with no outside daylength influence, a 10 to 12 hour day is used.

If the house has outside light leaking in that will influence the birds, the day length must be determined by finding the longest day between 6 and 18 weeks of age from at sunrise and sunset table for your location. If the flock is grown with outdoor access or open sided housing, add 30 minutes prior to the sunrise time and 30 minutes after the sunset time to account for twilight. Primary breeder management guides, breeder representatives, and charts of local sunrise/sunset times are sources of information for determining the day length to use.


Each primary breeder has determined the appropriate body weight for stimulating their strain of bird into production with increasing day length. This weight can be found in the breeder’s management guide. Stimulation target weight is usually around 17 to 18 weeks of age. It is important to not increase day length until the stimulation body weight is reached in order to prevent reproductive problems if birds are stimulated too early or too late.

When the target body weight is reached, increase day length used during growing by 30 minutes per week at least for 4 weeks. If a day length of 16 hours has not been reached at that point, continue the increase at the rate of 15 minutes per week until at least a 16-hour day length is reached.

Examples of Lighting Schedules

Example 1

Week Day Length Light Clock
On Off
1 22 hours 1:00 am 11:00 pm
2 20 hours 2:00 am 10:00 pm
3 18 hours 3:00 am 9:00 pm
4 16 hours 4:00 am 8:00 pm
5 14 hours 5:00 am 7:00 pm
  6-17 (2.90 lbs) 12 hours 6:00 am 6:00 pm
18 13 hours 5:00 am 6:00 pm
19 14 hours 5:00 am 7:00 pm
20 15 hours 5:00 am 8:00 pm
21 15.25 hours 5:00 am 8:15 pm
22 15.5 hours 5:00 am 8:30 pm
23 15.75 hours 5:00 am 8:45 pm
24 16 hours 5:00 am 9:00 pm
25 16.25 hours 4:45 am 9:00 pm
26 16.5 hours 4:30 am 9:00 pm

Example 2
Open house, January 15 hatch date, Lancaster PA, 40° latitudes. The longest day would be May 8 (16 weeks) which is sunrise at 4:30 am and sunset at 7:30 pm twilight included.

Week Day Length Light Clock
On Off
1 22 hours 1:00 am 11:00 pm
2 18 hours 3:00 am 9:00 pm
3 16 hours 4:00 am 8:00 pm
4-16 (2.90 lbs) 15 hours 4:30 am 7:30 pm
17 15.5 hours 4:15 am 7:45 pm
18 16 hours 4:00 am 8:00 pm
19 16.5 hours 3:45 am 8:15 pm
20 17 hours 3:30 am 8:30 pm

Eric Gingerich DVM
Diamond Technical Services Specialist – Poultry