University of California, Cooperative Extension


Revised September 2002

 Ralph A. Ernst, Extension Poultry Specialist, Animal Science Department, University of California, Davis CA 95616


Lighting programs are among the most important environmental management tools affecting flock performance. As there is an interaction between lighting programs used during the growing and laying period, it is important to plan a coordinated program for the life of each flock. This publication addresses lighting program decision making during the growing period. For information on lighting during the laying period request Poultry Fact Sheet No.14.

Sexual Maturity (age at 50% egg production)

The age at which pullets mature has a direct influence on their performance. Research has shown that each genetic stock has an optimum age at sexual maturity (+ or - 5 days) to produce the maximum possible egg mass (egg number x egg weight). Managers should continually evaluate the optimum age to light stimulate pullets even if they are using the same strain because breeders are continually selecting for earlier sexual maturity.

Producers usually want a lighting program which will maximize the value of eggs produced by the flock during the subsequent production cycle. This optimum program may differ with genetic stock, cycle length, housing date and possibly other factors.

The age at sexual maturity is affected to some extent by any changes in photoperiod which occur between hatch and subsequent photostimulation. Relatively consistent effects on age of sexual maturity have been demonstrated using 24 hour photo-schedules. Three types of lighting programs have been studied in which day-length either a) remains constant, b) increases or decreases gradually in small increments, or c) changes abruptly by several hours.

A. Constant day-lengths. When pullets are reared under constant day-length, sexual maturity depends on the duration of the light phase with 10, 12, or 14 hour day-lengths resulting in the earliest sexual maturity. Shorter or longer day-lengths result in later sexual maturity. In commercial practice day-lengths from 6 to 18 hours have been used successfully to raise replacement pullets. A day-length of 8 hours is probably the most commonly used constant day-length program. This program is moderately restrictive of age at sexual maturity and allows the manager to change pullets to a photo stimulatory program at any age desired. This provides some flexibility so that sexual maturity can be advanced or delayed depending on current egg prices or demand for eggs. Program 1 in Figure 1 illustrates a program which utilizes constant day length.


B. Decreasing day-lengths. When compared to gradually increasing or constant day-length, gradual decreases in day-length during the growing period consistently delay sexual maturity. Differences in sexual maturity of as much as 5 weeks have been observed when increasing and decreasing day-lengths were compared. Step-down lighting programs in which the light phase is reduced to less than 10 hours per day are more restrictive than those ending with 12 to 14 hour day-lengths. Decreasing day-lengths are most often used when pullets are grown in open-type housing without light control, however, constant day-length programs can also be used in these situations. Program 2 in Figure 1 is an example of a typical program using decreasing day-length.

C. Abrupt changes in day-length. Abrupt changes in day-length are sometimes made during the growing period with the assumption that they will have little affect on sexual maturity; however, research has shown that decreases in day-length as early as 3 weeks of age will delay sexual maturity. Abrupt increases or decreases in day-length have a much greater affect on age at sexual maturity if they occur at older ages but before egg production begins. Program 3 in Figure 1 is an example of a typical program using abrupt changes in day-length.

Housing Type

In conventional houses, without light control, the only programs possible are those which utilize a day-length equal to or longer than the shortest day-length which will occur during the growing period. A table showing sunrise, sunset and day-length at your latitude is invaluable for use in designing pullet lighting programs for open housing. Detailed information is available in U.C. Leaflet No. 21067, Lighting For Poultry.

Light Intensity and Cannibalism

Lower light intensities tend to reduce picking and cannibalism. This is particularly true at intensities below 5 foot candles (or about 50 lux). A minimum light intensity of 0.5 foot candles measured at the feed trough level is adequate for developing pullets, however, the lighting system should be designed with some tolerance because lamp output declines in old lamps, and is further reduced by dust and dirt on the lamps.

Red lamps have been used for growing pullets at various times with the idea that they will reduce cannibalism, however, research has shown that this reduces the persistence of egg production. For this reason and because red lamps are less energy efficient, they are not recommended for replacement pullets.

Choosing Lamps

Any light source could probably be used to light poultry. The more energy efficient types of lamps are recommended to reduce costs. For poultry houses with low mounting heights the new PL type warm white fluorescent lamps of 5 to 15 watts have proven to be an excellent choice. Their lower wattage and light output per lamp result in a more uniform distribution of light intensity while retaining the high efficiency of fluorescent lamps. They are available with a standard screw-type base so that they can be used to replace incandescent lamps. A recent study of PL type lamp performance in commercial poultry houses showed that the lamps had retained 96 percent of their original light output after one year, and 90 percent after two years of use. In houses where lamps can be mounted 12 to 20 feet above the birds, larger wattage fluorescent lamps are an excellent choice.

Energy Efficient Programs

When pullets in light controlled houses are provided a constant day-length of 8 hours this light period can be divided into short cycles of 15 minutes of light and 45 minutes of dark. Pullets perceive the intermittent photoperiods the same as a constant photoperiod. This program has been extensively researched by Purina Mills and is called a Bio-mittent® program. It is recommended for replacement pullets from 3 weeks of age until a stimulatory photoperiod is started.

This program reduces the time lights are on from 8 hours to 2 hours and 15 minutes per day for a savings of about 75 percent in lighting costs. Under experimental conditions this program has resulted in a decrease in feed consumption and slightly higher pullet weights at 20 weeks of age without detrimental effects on subsequent performance.

The same intermittent schedule can be used during the period when artificial light must be provided for a step-down lighting program. The light cycle must always start and end with at least 15 minutes light. Longer light periods within the light phase have no effect on sexual development. Therefore, you can turn lights on anytime during the skeleton photoperiod to service birds or equipment. Keep in mind that feed and light savings will not be realized when lights are on. Bio-mittent® light could be applied between 3 weeks of age and age of photostimulation with any of the programs shown in Figure 1.

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