An important element in modern poultry farming systems, is the lighting programme. Pullets, layers, breeders and broilers all have different needs. Starting with understanding the quality of light and what birds are seeing. Then choosing the right light source, as a bulb is not just a bulb. Various options are available at different costs, but also rewards.
By Ken Semon, North American technical service manager, Cobb-Vantress, USA
It comes as no surprise to any householder that advancements in lighting technology are being made at a feverish pace. Choosing a light source is a very different experience to a few years ago. Today, incandescent light bulbs are being phased out by more energy efficient alternatives including compact florescent bulbs (CFL) and light emitting diodes (LED), available in a full range of shapes and sizes depending on intended use. Whether purchasing lighting for the home or poultry house, it's important to understand the differences between light sources and the terminology often included on light bulb packaging.
Being a knowledgeable consumer in choosing a light source can not only potentially lower your electric bill, but also impact on flock performance. It's important to choose the correct light source depending on whether broilers, pullets or hens are being reared.
High on the list of important selection criteria include the type of bulb, its wattage, lumen output or intensity, lumen/ watt ratio, temperature (°K), cost, lifespan and warranty.
What poultry growers need to consider when choosing lighting
The driving force behind advances in lighting technology is energy conservation. The primary factor in a power bill is electricity cost x watts consumed. Simply put, the easiest way to reduce your electric bill is to reduce watt consumption. However, when it comes to poultry production, it's not so simple. Other factors must be considered such as lumen output, cost, lifespan, warranty and quality. Table 1 shows a comparison of several different types of bulbs and how they compare in each of these criteria.
[PDF: Table 1: Summary of table bulbs]
While the upfront cost for CFL and LED bulbs is considerably higher than for incandescent bulbs, it's easy to see from the table why they have gained acceptance in recent years. They are much more efficient in terms of the lumen/watt ratio and additionally have a much longer life expectancy than incandescent bulbs. Simply put, despite the higher initial cost, CFL and LED bulbs are far more efficient and will cost less in the long run.
High pressure sodium (HPS) bulbs, commonly used in open truss hen houses, have the highest lumen/ watt ratio; however they are also the most expensive bulb on the list. New house construction and retrofits are moving away from using HPS bulbs and towards either CFL or LED bulbs. In countries where solid side wall housing is common, new hen houses (12 m width) are being equipped with two rows of 18 watt LED tube lighting with 4 metre spacing.
Measuring light intensity at bird level
It's important to recognise that broilers, pullets and hens have different lighting requirements when it comes to intensity. Light output, or lumens, can be measured with a light metre but not all light metres have the same sensitivity. It's important to use the correct light metre for maximum accuracy considering the type of bulb used (CFL versus LED). The standard units of light intensity measured in poultry houses are either the
foot-candle (FC) or lux (1 FC equals approximately 10 lux).
Light intensity measured at bird level should be uniform throughout the house from side to side, front to back. Careful consideration should be given to light bulb placement since intensity quickly falls off as the distance from the bulb increases and, likewise, intensity rapidly increases the closer to the bulb. Typical bulb spacing is usually around 20 ft (6.5 m) centres, however enhanced uniformity can be achieved by placing bulbs closer together. Floor light intensity is greatly affected by bulb placement/ ceiling height and bulb design (lateral light dispersion).
How to reduce lumen depreciation in poultry houses
All light bulbs lose light intensity over time, and the rate of depreciation varies greatly depending on bulb type and quality. Physical depreciation over time can't be controlled. Observed depreciation in commercial houses can range from 4-8% per year for LED's and 12-18% per year for CFL's. However, depreciation due to excessive dust and dirt accumulation that can potentially reduce luminosity from 10-20% can be controlled by cleaning bulbs between flocks. As illustrated by table 2, a typical 100 watt incandescent bulb produces approximately 1600 lumens. A similar intensity can be achieved with a 23-26 watt CFL or 16-20 watt LED bulb.
[PDF Table 2: Equivalent Lumen Output/Light Source.]
Effect of colour, temperature and wavelength on poultry production
Bulb temperature is specified in degrees Kelvin. Bulbs with a high Kelvin rating (>5,000°K) will have a bluish hue, while those with a low Kelvin rating (2,200-2,700°K) will have a more yellowish hue to the human eye (Figure 1). The relationship between wavelength and colour/ temperature (°K) is the lower the temperature, the longer the wavelength.
[PDF: Figure 1: Light spectrum - Artifical light]
Colour, temperature and wavelength are important characteristics in poultry production as the longer wavelengths are necessary to stimulate photoreceptors and the pituitary gland, resulting in reproductive hormone release necessary for sexual development and egg production (Figure 2). Natural sunlight is a blend of all colour wavelengths although with a slight tilt toward red and infrared making it the perfect light for photo stimulation (Figure 3). Light bulbs in the 2,200-2,700°K range are manufactured to mimic natural sunlight as closely as possible.
[PFD: Figure 2: Human and poultry spectral sensitivity | Figure 3: Natural sunlight spectrum]
Due to this fact, it is recommended to use bulbs with 2,700°K or less in hen houses to stimulate egg production (photo 1), while broiler houses typically use bulbs rated between 3,000-5,000°K (photo 2). Light frequencies can be read with a Spectroradiometer.
Cost savings per flock
A 2009 study at Auburn University showed that replacing 32 HPS bulbs with 100- 23 watt CFL bulbs (1600 lumens each) resulted in a grower savings of $1,890/ flock or ~$6.00/ day! This study was done using an electricity cost of $0.11/ kWh, average for the location where the study was conducted. Considering that the cost of electricity in many countries far exceeds this, the savings per flock will be much greater. A point to note in the study is that the CFL bulbs were placed in two rows on 10 ft (3.25 m) centres, 1-1.5 ft (0.3 – 0.45 m) off slat edge (total of 84 bulbs) down the house length. Eight supplemental bulbs were used per side at the cool cell (six bulbs) and fan ends (two bulbs). Light intensity was measured to be between 5-8 foot-candles with no shadows.
Tables 3 and 4 illustrate the annual cost of hen house lighting per bulb at various power rates, and per hen house (@ $0.11/ kWh).
[PDF: Table 3: Annual cost of hen house lights (per bulb) (courtesy Dr Gene Simpson, Auburn University) Assuming ~5,000 hrs./flock, full intensity (44 week cycle). | Table 4: Annual power cost and savings for hen house lights (courtesy Dr Gene Simpson, Auburn University) Assuming 5,000 hrs./flock, full intensity, 40' x 500' house.]
Bulb of choice
The future for poultry house lighting will continue to shift in the direction of CFL and LED bulbs due to energy efficiency. It appears likely that LED bulbs will eventually become the bulb of choice as quality standards continue to improve and prices come down. The many advantages of LED bulbs including wattage draw, lifespan, warranty and in some instances rebate programmes make it feasible to consider LED bulbs in all new poultry house construction. The one note of caution when choosing LED bulbs for use in clear curtain-sided hen houses, common throughout the US industry, is to ensure sufficient, uniform light intensity that stimulates hens into production. Growers need to make wise business decisions at all times, and choosing the correct light source will pay dividends in energy savings and enhanced performance.
[Featured in World Poultry magazine no. 8 - 2014]