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Basic Rules for Lighting Programs

Guidelines for growing period
Start pullets with 20 to 22 hours of continuous and bright (30 to 50 lux, 3 to 5 foot-candles) light during the first week of age. Alternatively, an intermittent lighting program (4 hours of light followed by 2 hours of darkness) can be used during the first week of age. The dark period (or periods) serves as 'resting time' and helps strong chicks show the weak chicks how to find feed and water.

The light intensity should be 30 lux (3 foot-candles) during the first week of age, after which it can be reduced to 5 to 10 lux (0.5 to 1.0 foot-candles) in cages or to 15 lux (1.5 foot-candles) when grown on the floor. The higher light intensity for floor-grown birds will allow the birds enough light to navigate their environment. In cages, there should be 10 lux (1.0 foot-candles) at the feeder and 5 lux (0.5 foot-candles) inside the cage.

Reduce the day length weekly to reach 9 to 10 hours at 10 weeks of age or, if longer, the day length dictated by greatest natural day length in open or brown-out houses. In Hy-Line Brown and CV-22 varieties, a constant day length of 9 hours may be used to control excessive body weight after 10 weeks of age.

The light intensity in the grow and lay houses should be similar because pullets can be stimulated to start egg production by an increase in light intensity, even if the day length is unchanged. Therefore, the light intensity in the grow house should be gradually increased in increments of 5 lux (0.5 foot-candles) per week to the intensity used in the lay house, starting 2 to 3 weeks before the pullets are moved.

Guidelines for laying period
Onset of sexual maturity (egg production) generally depends on 4 requirements:

  • a minimum chronological age which is genetically determined (17 weeks)
  • a minimum body weight (see tables of 18-week target body weight for individual Hy-Line varieties)
  • a nutrient and energy consumption to support production
  • a constant or increasing day length of at least 12 hours

Light stimulation should not be provided until flocks reach the optimum body weight (see tables of 18-week target body weight for individual Hy-Line varieties). Flocks which are light-stimulated into production at lower body weights will likely produce below normal egg weight and suffer from reduced peak production and post-peak dips in production.

Timing of light stimulation can be used as a tool to help attain desired egg size. In general, earlier light stimulation will result in a few more eggs per hen, but at a tradeoff for slightly reduced egg weight. Later light stimulation will result in a few less total eggs, but a slightly larger egg weight earlier in production. In this way, lighting programs can be customized to best meet the egg size demand of a particular market.

Provide light stimulation when the target body weight is reached, usually around 17 to 19 weeks of age. The appropriate target body weight depends in part on the variety of hen and in part the desired egg size. Stimulation at a relatively early age or low body weight will result in production of a greater number of eggs with a lower average egg size, which will negatively impact chick quality. Stimulation at an older age or a heavier body weight will produce a few less eggs, but of greater average egg size.

The initial light increase should be no less than 1 hour (especially in open or brown-out houses). Increase the day length by 15 to 30 minutes per week or once every 2 weeks until 16 hours of light is reached. Preferably, the period of increasing day length stimulation should last until peak production (i.e., until about 30 weeks of age). The light intensity at housing should be 15 to 30 lux (1.5 to 3.0 foot-candles) in light-controlled houses and 30 to 40 lux (3 to 4 foot-candles) in open-sided houses.

Allow no decrease in day length or light intensity in adult layers. Such decreases in day length will adversely affect egg production.

Guidelines for housing styles
It is necessary to first determine what style of houses are being used regarding light control for both growing and laying. For the purpose of designing a flock lighting program, each house has to be designated either dark-out or open.

Dark-out means there is essentially no outside light coming in the house that would physiologically affect the flock's maturity. In that case, the outside natural day length can be ignored and the lighting program be planned using only artificial lights. That said, it is beneficial to consider and synchronize the time of lights-on and -off with the natural sunrise and sunset, respectively, under the constraints of the artificial day length.

Open house styles mean there are windows, curtains, or even just enough light leakage through fans and air vents that allow outside natural daylight to significantly illuminate the interior of the house. In many cases this cannot be avoided, but a lighting program with the desired light patterns can still be planned using artificial interior lighting added to the natural daylight changes occurring outside.

Sometimes it is not clear whether a house is sufficiently dark-out or not, and these houses are often called brown-out. It is mostly light-controlled, but not totally dark, as some light gets in through the ventilation, etc. The question is how to consider the house, open or dark-out?

  • One method is to measure the light intensity with a light meter. Compare the maximum mid-day light intensity with the lights on to the intensity with the lights off (measuring just the light leakage from outside). If the light leakage is less than 10% of the maximum value, it is probably insignificant in stimulating the birds and can be ignored (i.e,. consider the house dark-out). However, if it is more than 10% of that maximum value, it probably needs to be considered open.
  • Another method is just to observe the flock's activity. With the lights off, will the flock awaken and become active when the sun rises, just from light leaking in from outside? If so, then consider the house as open for this purpose. Even with these guidelines, it is still a judgment call whether a significant portion of the flock is being affected by outside light.


Light-controlled growing to light-controlled laying

  • Step-down day length from 20-22 hours of light the first week of age to 9-10 hours of light at 10 weeks of age and hold constant.
  • Increase day length 1 hour at the 18-week body weight target. Add 15-30 minutes per week until 16 hours total light is reached and hold constant.

Light-controlled growing to open or brown-out laying

  • Step-down day length from 20-22 hours of light the first week of age to either
    • 9-10 hours of light at 10 weeks of age or
    • 1 hour less than the natural day length the flock will be exposed to after moving to the layer house.
  • Increase day length to
    • natural day length or
    • a minimum increase of 1 hour at the 18-week body weight target.
  • Add 15-30 minutes per week (or every 2 weeks) until either
    • 16 hours total light or
    • at least the longest natural day length of the year.

Open or brown-out growing to light-controlled or brown-out laying

  • Step-down day length from 20-22 hours of light the first week of age to either
    • 9-10 hours of light at 10 weeks of age or, if longer,
    • the longest natural day length the flock will be exposed to from 8-18 weeks of age.
  • Increase day length 1 hour at the 18-week body weight target.
  • Add 15-30 minutes per week (or every 2 weeks) until either
    • 16 hours total light or
    • at least the longest natural day length of the year for brown-out. 

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