Lighting Programs in Broiler Breeders and Dark Out

Providing an optimal light program during pullet rearing and breeder production starts with understanding how chickens are stimulated by light. Light intensity, light coloring and day length all play a major role in preventing or stimulating sexual maturation. Ideal day length for rearing pullets is 8 hours to prevent early sexual development and therefore assure that flocks begin lay and maintain egg production in a more uniform manner. Transitioning pullet operations to solid side wall dark out facilities requires attention to detail regarding light tight facilities. No light leaks from outside sources are acceptable in pullet housing where day length during the rearing period should not exceed 8 hours.

Even a small light leak which allows tiny light rays into the barn is enough light to stimulate exposed pullets into early lay and lead to an overall reduction in egg numbers through 65 weeks of age. In addition to assuring that day length is strictly controlled, it is also important that intensity should be maintained after the initial brooding period to 5 lux or 0.5 foot candles. This low light intensity reduces excessive activity in flocks which will improve uniformity, livability and feed conversion. A second important consideration is assuring light quality is consistent throughout the facility. Light sources which do not provide uniform light output or cause dark or bright areas will result in excessive pullet activity and can even cause birds to dig holes in the bedding material in response to the non-uniform light and result in an uneven floor level around feeder lines that can limit feeder access. Light intensity should not vary more than 20-30% from the lightest to darkest areas of the barn. A third consideration is the color of the light or Kelvin. Kelvin is the measurement of how warm or cool a light source is with incandescent bulbs typically having a 2700 K or warm orange red color; compact fluorescent bulbs with a 4100 K which is a neutral light color or temperature and then some of the newer LED technology having as high as a 5000 or 6000 K which is a very cool or blue white light color or temperature. The ideal kelvin range for pullets is around 4,000 K which has been shown to have a calming effect on the birds resulting in less activity. Preparing birds for the lay cycle involves three major points, increasing day length and light intensity and providing a light color that stimulates reproduction. Stimulating birds into lay should begin around 20-21 weeks with a day length increase from 8 hours of light to 11-13 hours. The eleven hours of day length is common for production near the equator while 13 hour day length is common in the US for initial light stimulation period. Light intensity should increase from the pullet house level of 5 lux to 80 to 100 lux (8 to 10 foot candles). For best results it is important to maximize the degree of light intensity contrast between the rearing and production barns and to also minimize photo refractory periods within a 24 hour period. Photorefractions refers to the drop in light intensity which can occur if birds are housed in open sided or curtained houses. During the day, light intensity can be as much as 200 lux (20 footcandles). Yet once the sun goes down, if the artificial light quality is poor, light intensity may drop to as little as 5 to 10 lux (0.5 or 1 foot candles) and the drop in light intensity is almost perceived by the birds as part of the dark period. It is also important in the breeder barn that the Kelvin rating of the light source is in the warm range or below 3000 K since this is important for stimulating follicle development or reproduction. This is one reason why sodium lamps are commonly used in breeder houses, they are a warm or low Kelvin light source (2100K). Never decrease intensity or duration of light once birds are placed into production. 

Lighting sources are also very different in energy usage with incandescent bulbs having the highest cost of operation although they are the cheapest to purchase. The high pressure sodium lamps are more efficient than incandescent bulbs but do require a ballast which increases initial cost. Compact fluorescent bulbs use about 60-65% of the energy as incandescent bulbs (with similar wattage ratings). However fluorescent bulbs tend to be more sensitive to power fluctuations and low level dimming and while relatively inexpensive, they do have a higher replacement rate than incandescent bulbs. LED or light emitting diodes is a new light technology that is gaining popularity in the US primarily because of bulb durability, light quality and the high efficiency level as compared to incandescent bulbs (~80% more efficient than incandescent bulbs) Currently LED bulbs are 40-80 times more expensive than incandescent bulbs but as this technology becomes more widely adapted in the poultry industry, new prototypes are being introduced that are more economical. Key considerations for LED bulbs is assuring the bulbs are designed for poultry house use, have no openings for heat dissipation which can allow dirt or moisture to enter the bulb, verify light angle output to assure adequate light coverage (minimum of 140-160° light angle output is recommended) and that the bulbs are compatible with existing dimmers.