Role of light on egg production
The egg production is associated with the length and intensity of the light received by the bird daily. Light stimulates the anterior lobe of the pituitary gland through optic nerve for the release of FSH and LH. Light energy also penetrates through the skull, skin and feathers. FSH increases the growth of the ovarian follicles. Upon reaching maturity, the ovum is released by the action of LH.
Important points regarding light
Candela (Candle)
A candela is the unit of luminous intensity of a light source in a specified direction
Lumen
The lumen is defined as the rate at which light falls on a square foot area surface which is equally distant one foot from a source whose intensity is one candela.
Foot-candle
Illumination on a surface is measured in foot-candles. A foot candle is defined as the intensity of light striking each and every point on a segment of the inside surface of an imaginary one-foot radius sphere with a one candlepower source at the center. Thus one foot candle equals one lumen per square foot.
Lux
A lux of light intensity is equal to one lumen per square foot.
1 foot candle = 10.76 lux
Types of light
There are four common light types used in poultry houses are,
Light management
The manner in which lights are installed in the poultry house has a role on their efficiency. Some of the important points regarding fixing bulbs in poultry houses are,
Light effects during growing period
Decreasing the length of light day during growing period will lead to
Light restriction alone delays the sexual maturity at the maximum of 3 weeks. If feed restriction is combined with light restriction we can delay up to 4 weeks period.
Light effects during laying period
Birds reared under increased day-light produce more eggs due to the release of FSH and LH from the pituitary. Brightness of light also has influence on egg production. On practical conditions, 1 ft candle light intensity is needed in layer houses. In multi-duck cage system, minimum of 0.5 foot candle light intensity is needed at the lower deck. For maximum egg production, 16 hours light is needed during peak egg production period. Reducing photoperiod during laying period seriously affects egg production. The artificial light can be given either in the morning, evening or both morning and evening.
Combination growing-laying light programs
Two important points to be consider regarding lighting are,
In-season flocks
Those birds grown during a period when the length of the natural light day is decreasing, at least during the last part of their growing cycle are called in-season flocks. As a general rule, chicks hatched between March 1st and August 31st in the Northern Hemisphere is called in-season flocks.
Out-season flocks
Chicks hatched between September 1st and February 28th are called out-season flocks since their growing period falls on increasing light-day.
Instructions for growing and laying light programs in open-sided houses
a) In-season flock
No artificial light is needed up to 20 weeks (in case of meat-type breeders 22 weeks). At 20 weeks of age increase the light to 13 hours. Then add 1 hr per week until it attains 16 hours light.
b) Out-season flock
Two methods can be adopted
i) Constant light-day program
Determine the length of the longest natural light day before the pullets reach 20 weeks of age. Maintain this period of daily light hours from the 3rd day until 20 weeks by supplementing artificial light with natural light. Then increase 1 hour of light at this stage and increase 1 hour every week until it reaches 16 hours total light period.
ii) Decreasing day-light program
Determine the total natural day-light hours when the pullets reach 20 weeks of age. Then add 7 hours. This represents the length of the light day from the 3rd day. Thereafter reduce the length of light day by 20 minutes per week. At 20 weeks of age increase the length of the light day by 1 hour. Then increase 1 hour per week until it attains 16 hours light per day.
Photo-refractoriness
Photo-refractoriness is a condition in which the bird is not capable of responding to long day lengths. Greater the stimulatory day length, the sooner and more pronounced the reduction in egg production due to photo-refractoriness.
Ahemeral lighting programs
When the total period of light and dark not equals 24 hours we can call it as ahemeral lighting cycle. There are two types: Longer day (14 hr light + 14 hr dark) and shorter day (11 hr light + 11 hr dark). Longer day cycle increases egg shell quality where as, shorter day cycle increases the egg production by 2%. However, these cycles are not compatible with normal working schedule and needs light proof houses.
