Understanding lighting in broiler houses

(Editor’s note: Jennifer Timmons is an assistant professor at the University of Maryland Eastern Shore.)

As poultry growers you are well aware that the simple process of providing light to birds has become a little more complex during the last 20 years.
Lighting programs have evolved into much more than just screwing in a light bulb and turning on a switch. So why have lighting programs become more detailed? Why do birds even need light?
When it comes to chickens there are three main functions of light. The first is to facilitate sight so that birds are able to navigate their environment. The second function is to stimulate the bird’s internal cycles due to changing hours of daylight. This allows the birds to synchronize essential physiological functions, such as body temperature and various metabolic steps that assist with feeding and digestion. The third function of light is to initiate hormone release for growth rate and sexual maturity.
Lighting programs not only have an important role in bird health and performance, but they are also an important component of animal welfare guidelines and audit checklists.
In addition to the several benefits of light, darkness also plays an important role in bird health and performance. It has been reported that melatonin, a hormone produced by the pineal gland (a small gland located in the brain) and linked with the bird’s biological clock, may also be associated with immune function and disease resistance.
Melatonin is produced by animals only during dark periods, and it has been reported that birds provided with sufficient dark periods have fewer health related problems compared to birds exposed to continuous light.
There are three important aspects of the lighting environment: light intensity, duration, and wavelength. Light intensity is measured in terms of foot-candles (light level at the working surface). A foot-candle is defined as the amount of illumination by a standard candle at a distance of one foot.
The light output of a bulb is measured in lumens, and light intensity (foot-candles) is directly proportional to lumen output.
For example, if you desire 1.0 foot-candle in your poultry house and you are getting 0.5 foot-candle near the sidewall with a 450 lumen bulb, you will need to install bulbs that produce at least 900 lumens.
Light meters can be used to measure light intensity in the poultry house. In order to obtain the most accurate measurement, it is important to measure light intensity at bird level and to angle the meter toward the nearest or brightest source of light. Typically growers are interested in making sure that all birds receive at least the minimum recommended level of light.
Therefore it is recommended to measure light intensity near the side wall half way between light bulbs where it is the darkest. Researchers from the University of Georgia, Mike Czarick and Brian Fairchild, reported that a variation of 20 percent or less in light intensity should be expected with a properly installed lighting system.
If you wish to maintain a specific light intensity, it is recommended to use the lowest light intensity found in the house as the measurement. In fact once the specified light intensity is achieved, the dimmer can be marked to maintain that light intensity for future flocks.
Although it is recommended to check light intensities a couple of times a year, since bulbs will become dirty overtime and can decrease the level of light they produce by 20% or more.
If you decide to purchase a light meter, it is important to buy a meter that can accurately measure light intensities below 0.1 foot-candles because most poultry companies recommend maintaining low light intensities in broiler houses (after brooding). Czarick and Fairchild recommend a light meter with a resolution of 0.01 foot-candles and have an accuracy of around 3 percent.
There are a wide variety of lighting programs available and many growers have asked the question: What is optimal light intensity to achieve optimal performance? Most research results have suggested that it is best to have a minimum of two foot-candles of light during the brooding period.
When it comes to older birds however, optimal light intensity will depend on a number of factors such as breed, bird size, and number of hours of light each day. It is difficult to compare studies that report results of light intensity on performance because many of these studies use different breeds, raise birds to different ages and expose birds to different photoperiod lengths. You cannot compare “apples to apples” with these studies, and as a result discussion on this topic continues.
In addition to lighting schedule and light intensity, wavelength is also an important factor that influences bird performance. It has been reported that different colors have many different effects on behavior, growth, and reproduction. However, research results are inconsistent because of study differences in light source, light schedule, breed, and age of birds.
Another factor to consider as we enter into the summer months is the light that enters the house through the tunnel fans. When tunnel fans are in the sidewall, a limited number of birds may be exposed to high light levels. However, more birds are exposed to high levels of light when tunnel fans are in the end wall. This typically is not an issue with younger birds or when moderate to high light intensities are used.
However, the behavior of older bird raised during the summer months may be influenced by the high intensity light entering through the end wall tunnel fans.
It is well documented that feed and water consumption are related. Typically water consumption will trend with feed consumption. As water consumption increases, feed consumption increases and vice versa. Additionally, most growers observe there are typical drinking and eating patterns for birds on lighting programs.
The higher intensity light entering through the tunnel fans may influence water (and feed consumption). Czarick and Fairchild reported an example of this scenario in a 2016 University of Georgia factsheet.
Birds given a six-hour dark period from 9 p.m. to 3 a.m. did not respond with increasing water consumption when the lights came back on at 3 a.m., but instead responded to light from the morning sunrise.
This suggests that the higher intensity light received from the tunnel fans prolonged the dark period perceived by the birds and thus altered their water consumption.
This reduction in water intake can result in lower feed consumption, and may influence the weight of the birds at market age.
The authors more recently reported the results of a preliminary study which compared the performance of 14-day-old chicks provided 24 hours of light at placement to the performance of chicks provided 20 hours of light and 4 hours of dark.
The authors reported no differences in weight and feed conversion of the chicks raised with the two lighting programs.
Additional studies using different lighting programs during brooding will be conducted with market age broilers.
It is clear the lighting plays an important role in a broiler’s environment. However, there is more research needed in this area especially as new lighting technology emerges to address increasing energy costs, and more is learned how bird behavior is influenced by lighting programs.