BY
Role of light on egg production
Birds are more sensitive to light compared to humans. Hence, effective Lighting Management is essential in poultry management. Lighting can influence the onset of lay, early egg size and the total number of eggs produced. Lighting varies from differing environments including both open and brown houses. Care should be taken to maintain light intensity at the same levels or even higher during the last weeks of rearing. 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
- Wavelength between 400 and 700 millimicrons (nanometer) ® Visible to eye
- The longer wavelengths (Red) of visible light are more capable of reaching the brain than shorter wavelengths.
- The intensity of sun’s light rays varied due to
- Position of the sun
- Cloudiness
- Dust and moisture in the air
- Length of day light varies due to the relative position of the earth to the sun
In Northern Hemisphere
- In Northern Hemisphere
- Cloudiness
- Dust and moisture in the air
- Length of day light varies ® due to the relative position of the earth to the sun
In Northern Hemisphere
- June 21st Longest day of the year
- December 21st Shortest day of the year
- (In southern hemisphere it is reversed)
- Day light occurs from 15 to 30 minutes before sunrise and darkness occurs 15 to 30 minutes after sunset is due to the curvature of earth’s surface and thus the length of light day is somewhat longer than the hours between sunrise and sunset. But the time between sunrise and sunset is usually considered as the “light day”
Types of light
There are four common light types used in poultry houses are
- Incandescent – Cheapest; necessitates reflectors, short bulb life (750-1000 hrs)
- Fluorescent – 3 to 4 times more efficient than incandescent bulbs; 10 times longer life than incandescent bulb
- Mercury vapor – Long life (24,000 hrs); requires several minutes to warm up; cannot be used in houses with low ceilings.
- Compact Fluorescent (CF) Lighting – More energy efficient. One-fifth energy of fluorescent light is needed to provide same light intensity (lumen)
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,
- The distance between bulbs should be 1½ times the distance from the bulb to the bird level.
- The distance from the bulbs to the outer edges of the house should be only ½ the distance between bulbs.
- In cage system, the bulbs should be placed in such a way that their rays fall on the feed and on the birds.
- Clean reflectors increase the light intensity at bird level by 50%, compared with no reflector.
- Avoid cone shape reflectors since they confine the light rays to limited area. Better to use flat type reflector with rounded edge.
- In case of deep litter system, the bulb is to be placed at 7-8’ height whereas in cage house, keep in aisle.
- Avoid hanging bulbs by a cord in open houses
- Very dirty bulbs emit about 1/3 less light than clean bulbs.
- Light bulbs should be cleaned once in two weeks.
Light effects during growing period
Decreasing the length of light day during growing period will lead to
- Increase the age at sexual maturity
- Increase the number of eggs laid during the first half of the egg production (but not in total number of eggs laid)
- Increase the size of the first eggs produced.
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,
- The length of the light day should never increase for growing pullets.
- The length of the light day should never decrease for laying pullets.
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
Instructions for growing and laying light programs in open-sided houses
- 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.
- Out-season flock
Two methods can be adopted
- 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.
- 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.
NB
In growing step down lighting from 3rd week onwards and bring to 12 hours lighting ( natural and if required artificial light ) 7th week onwards Stimulate lighting based on body weight. We advice you to stimulate light as soon• as the bird reaches 1100 grams of body weight. It is important that you do not increase the length of day until you are prepared to start• stimulation During production, it is essential not to decrease the length of day as it would affect• the outcome of the eggs Light stimulation also helps you either to delay production or increase egg weight at• the start While transferring pullets from dark out rearing facilities to alternative housing• systems with natural light stresses the birds.
LIGHT AND LIGHTING FOR POULTRY
Light is an important aspect of an animals environment. Avian species as well as mammalian species respond to light energy in a variety of ways, including growth and reproductive performance. The value of regulating the photoperiod of poultry and livestock to stimulate reproduction has been recognized for many years and is used regularly by commercial poultry and livestock farmers. For chickens there are three major functions of light: 1. to facilitate sight, 2. to stimulate internal cycles due to day-length changes, and 3. to initiate hormone release. Providing light for chickens has become a little more complex during the last 15 years than just screwing in a bulb and flicking on a switch. Now there are a wide variety of lighting programs and devices available to poultry producers, each with its own characteristics and applicability to rearing chickens. However, before we get to the details, I have found that most people are slightly confused about what light is and what aspects of it are important to rearing poultry. I would therefore like to elaborate on this just a little.
WHAT IS LIGHT?
Visible light is just a tiny portion of the total electromagnetic spectrum, which includes radio waves, microwaves, x-rays and gamma rays. The light environment can be classified in three ways: wavelength, intensity and duration. Each of these aspects will be discussed relative to rearing poultry.
WAVELENGTH OR COLOR OF LIGHT
Research has shown that the color of light can have many different effects on behavior, growth and reproduction in poultry. Birds sense light through their eyes (retinal photoreceptors) and through photosensitive cells in the brain (extra-retinal photoreceptors). Since long wavelengths of light (towards red end of the spectrum) penetrate the skin and skull more efficiently than short wavelengths, it has been observed that growth and behavior are linked to retinal photoreception (and shorter wavelengths) whereas the reproduction has been linked to extra-retinal photoreceptors. From these observations it has been reported that blue light has a calming effect on birds, however, red has been used to reduce cannibalism and feather picking. It has also been shown that blue-green light stimulates growth in chickens while orange-red stimulates reproduction. Birds have pigmented oil droplets on their cone cells that correspond to peak sensitivities of 415 nm, violet; 460 nm, blue; 510 nm, green; and 560 nm, yellow for young birds with a peak at 580 nm, orange for adults. Recently, it has been shown that the lens of birds is transparent to light in the UVA range (320-400 nm). However, they probably see brightness of color different from humans. These facts are important to remember when selecting a light source for illuminating poultry.
The lighting industry uses four methods to describe light color but only one really applies to selecting lighting for poultry, chromaticity. Chromaticityis the measure of a light source’s warmth (warm light) or coolness (cool light) expressed in degrees Kelvin. The scale runs from 2000 to 7000K. Chromaticity values of 4000K and higher are considered cool (mostly blue light), those around 3500K or 3600K are called “balanced” or “neutral” and those of about 3000K or lower are considered warm (more red light). A color temperature designation is truly accurate only for an incandescent lamp because it produces a continuous spectrum. Fluorescent and HID (high-intensity discharge; HP Sodium and Metal Halide lamps) lamps are said to have a “correlated” (apparent) color temperature and are thus always described using the term correlated color temperature (CCT) (Knisley, 1990).
Chromaticity is the measure of a light sources’ warmth (warm light) or coolness (cool light) expressed in degrees Kelvin. The scale runs from 2000 to 7000K. Chromaticity values of 4000K and higher are considered cool (a lot of blue light), those around 3500K or 3600K are called “balanced” or “neutral” and those of about 3000K or lower are considered warm (more red light). A color temperature designation is truly accurate only for an incandescent lamp because it produces a continuous spectrum. Fluorescent and HID (high-intensity discharge; high pressure (HP) Sodium, Low pressure sodium and Metal Halide lamps) lamps are said to have a “correlated” (apparent) color temperature and are thus always described using the term correlated color temperature (CCT).
WHAT KIND OF LAMPS ARE AVAILABLE TO POULTRY PRODUCERS?
Incandescent, Fluorescent, Metal Halide and High-Pressure Sodium lamps are currently being used in poultry production facilities for laying hens, breeder flocks and growing meat birds. The incandescent bulb is the current standard by which others are compared, relative to poultry production.
Incandescent bulbs produce light by passing an electric current through a tungsten filament, heating it to incandescence. These lamps provide light energy over the entire visible spectrum, however much of the electrical energy is converted to heat energy as infrared. They have a light efficiency of about 8 – 24 lumens per watt and a rated life of about 750-2000 hours. A tungsten-halogen incandescent lamp will last about 3000 hours with an efficiency of about 20 lumens per watt.
Fluorescent lamps produce light by the passage of an electric current through a low-pressure vapor or gas contained within a glass tube. The ultraviolet radiation given off by the mercury-vapor arc stream produced along the length of the tube is absorbed by the phosphor material coating the inside of the glass tube, causing it to fluoresce at wavelengths that are seen as visible light. The wavelengths emitted depend upon the phosphors used in coating the tube. The new CF lamps all use a special triphosphor coating, resulting in light emitted in discrete wavelengths from each of the primary colors, red-orange, green and blue, giving an appearance of balanced white light. There are several styles of the CF lamps, including twin, quad and spiral tubes. They come in 5, 7, 9, 13, 16, 22, and 28 watt sizes with efficiencies of 50 to 69 lumens per watt and rated lifetimes of greater than 10,000 hours. Recent research has demonstrated that some may last more than 20,000 hours under poultry house conditions. However, these lamps will decrease their light output by about 20 – 30% over their lifetime, (Darre and Rock, 1995) and this must be considered upon initial installation. All fluorescent lamps require a ballast. The CF lamps have been used successfully in all types of poultry operations, including caged layers, (Darre, 1986) breeder flocks, growing broilers (Andrews and Zimmerman, 1990; Scheideler, 1990), growing pullets and turkeys. Research by Widowski, et al., (1992) indicated a preference for CF lamps over incandescent lamps by Leghorn layers.
Cold Cathode Flourescent Light (CCFL) is a tubular light that works by passing an electrical current through a gas or vapor, much like neon lighting. Cold cathode lights can come in many sizes and colors, and there are many advantages over neon and fluorescent lighting. The first advantage is that cold cathode lights do not get hot. Another is that a cold cathode light is up to five times brighter than neon lighting, and it has one of the longest lives of any lighting fixture at about 50,000 hours. Unlike incandescent bulbs, the longevity of one of these lights is not shortened by the repeated action of turning it on and off. Cold Cathode Lighting Systems are offered in several different systems for varying applications, with light outputs up to 709 lumens per linear foot (2340 lumens per meter). Dozens of pastel and neon colors are available, as well as a wide array of high-color-rendering white hues. Lastly, they are dimmable using current incandescent lamp dimmers. The disadvantage is their initial expense. There are also CCFL designed to replace long life incandescent lamps and lamps that are used in dimming applications. These CCFL lamps are virtually the same size and shape as the incandescent lamps they were designed to replace. They include an integrated miniature electronic ballast, fully dimmable to less than 5% .
High Pressure Sodium (HPS) lamps discharge an electric arc through a concentrated sodium vapor producing energy across the entire visible spectrum, but with the highest intensity in the yellow, orange and red regions. These are considered warm lights at about 2100K color temperature. They run at about 51-132 lumens per watt and come in wattages ranging from 35 to 1000. They have the longest rated life of all the lamps discussed, at about 24,000 hours. All HPS lamps require a ballast. These lamps require a warm up time to full illumination of between 5 and 15 minutes, which means that after a power outage, backup lighting may be necessary until full illumination has been achieved again. These lamps have been used successfully in poultry facilities, mostly in breeder houses and turkey facilities, with peaked roofs so that light distribution is more easily controlled (Andrews and Zimmerman, 1990).
Metal Halide (MH) lamps have ratings from 32 to 1500 watts and come in three different outer bulb finishes, clear, phosphor coated and diffuse. The MH lamps emit light across the entire visible spectrum, but are considered a cool light, having a lot of blue. They have efficiencies of about 80 to 100 lumens per watt and are rated at about 10,000 to 20,000 hours of life. MH lamps require a ballast also. Because these lamps must be mounted in a specific orientation (vertical or horizontal) they are not used much in the chicken house, but have been used in warehouse areas and egg handling rooms, where ceilings are high and efficient, bright lighting is required. These lamps also have a warm up period of between 5 and 15 minutes to achieve full illumination.
Light Emitting Diodes (LED) have been used for many applications where long life and reliability are required. Most run on low voltage (3.6 – 24 volts) and when put into an array, they can produce high light output in either a focused or wide angle beam. They come in many different colors, however there are currently two ways to make white light with LED’s. One method mixes multiple wavelengths of different LED’s to make white light (i.e. RGB); allowing the lighting designer to tune the white light to a specific color temperature, such as 2700K The second method uses a blue Indium-Gallium-Nitride (InGaN) LED with a phosphor coating to create white light. This is the method that results in the more commonly seen “white LED”. The LED arrays are relatively expensive, but are getting less expensive all the time. They are illuminated solely by the movement of electrons in a semiconductor material, and they last just as long as a standard transistor. Newer AC driven lamps are now becoming available.
The following table lists lamp types and some cost factors.
Figure 1. Lighting Source Comparison
INC CF CCFL MH HPS LED
Initial Cost Low Moderate Moderate High High Moderate
Operating Cost High Moderate Moderate Low Low Very Low
Efficiency* 8-24 50-69 50-100 80-100 51-132 51-115
Rated Life (hrs) 500-2000 10,000+ 50,000+ 15,000+ 24,000+ 50,000+
Color Temp (K) 2500 2700 Variable 3700-4000 2100 Variable
Efficiency is measured as the rated lumens per watt.
Figure 2. The spectral distribution of the incandescent, high pressure sodium, compact fluorescent and metal halide lamps
HOW BRIGHT AND HOW LONG?
Now that the physical aspects of the lamps have been discussed, it is time to turn our attention to intensity and duration.
LIGHTING LAYERS
Intensity: In natural light (window) housing the natural light is supplemented with 1.5 – 5.0 fc for the period when supplemental lighting is used. It has been found that birds exposed to very dim lights, say 3 hrs at.02 -.03 fc) prior to exposure to bright lights, say 8 hrs at .5 fc or more, might perceive this as sunrise and daylight and shift their biological clock as if exposed to 11 hours of normal light. However, the reverse, dim following bright, does not shift their perception. It appears that the threshold intensity for photostimulation is about .15 fc. However maximal egg production has been achieved at intensities between .5 and 1 fc.
The next important aspect is duration of light stimulation. Two rules exist for this.The next important aspect is duration of light stimulation. Two rules exist for this.
- Never Increase the duration or intensity of light during the growing period.
- Never Decrease the duration or intensity of light during the production period.
Duration depends upon the age of the chicken and type of housing you use. Chicks can be exposed to 21-23 hrs of continuous light at one and two days of age and then reduced to 15 or 16 hrs of light until the birds are three weeks of age. (Chicks have a very low fear response during their first three days of life and can be exposed to many environmental stimuli, such as new housing, light and dark, etc. without much adverse effect.) At three weeks of age, reduce the hours of light to 10-12 hours or as dictated by natural day length. In summer for open housing use decreasing hours of light up to six weeks of age and then hold constant to avoid delays in maturity. When target body weights are achieved start your stimulatory lighting program. Jump to 13 hours and then add 15-30 min per week until 16 hrs of light is reached. Light stimulation should continue until peak production is achieved.
However, according to Lewis et al. (1992) the sensitivity of the young pullet to an increase in photoperiod varies with age and is at a maximum between 9 and 12 weeks of age and thus increasing the photoperiod at or soon after 18 weeks has little effect on age at 50% lay. Therefore, the use of step-down – step-up lighting programs should be timed to bring the birds into lay at the age you wish, either early lay or late lay, starting the program between 9 and 12 weeks. With early lay you will get more, smaller eggs and with late lay you will get fewer, larger eggs, but the total egg mass at the end of lay will not be much different.
LIGHTING THE BROILER
Intensity: With blackout housing broilers can be exposed to 1 to 2 fc from day one to day three and then placed on .5 to 1 fc to processing. In natural light housing (window or curtain houses) the natural light is supplemented with .5 – 2.5 fc for the period when supplemental lighting is used. Duration depends upon the age of the chicken and type of housing you use. Broiler chicks can be exposed to 20-23 hrs of continuous light at one and two days of age and then reduced to 18 – 20 hrs of light until processed. Recent research has shown that darkness is just as important to the health and growth of birds as is light. During the dark phase, melatonin, a hormone released by the pineal gland, is released. Melatonin has been associated with immune function and disease resistance. Birds provided with sufficient dark periods have fewer health related problems, including sudden death, spiking mortality and leg problems.
WHERE SHOULD THE LAMPS BE PLACED IN MY BUILDING?
The distribution of light within your poultry facility will depend upon placement of the lamps. The lamps should be placed so that the maximum illumination value is spread over the largest area. This all depends upon the physical dimensions and equipment in your building. In both breeder/layer and broiler facilities, it is best to place the lamps such that the darkest areas have at least .5 -.75 fc of light. The number of feet between lamps will depend upon the size of the lamp and the physical surroundings of the building, such as walls, posts, ceiling reflectivity, etc. Just remember, your goal is to achieve even lighting throughout your building, at the desired brightness level for your birds. One last point, all the lamps described above, except the incandescent, will lose up to 20% of their original light output during their rated life, and must be considered in lamp placement (Darre and Rock, 1995). For example, if you desire no less than .5 fc at the darkest point and you use a CF lamp, at the end of the lamp life, or when dirty you may only have .4 fc or less. (If a lamp is rated at 100 lumens, it will have only 80 lumens toward the end of the lamp life.) Incandescent lamps will loose some but less of their original illumination value. Dirty lamps will also decrease light output, by as much as 15 to 20%, therefore it is important to clean the lamps off at least once per week.
