It comes as no surprise to any grower that advancements in lighting technology are being made at a feverish pace. Choosing a light source is a very different experience now than it was 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. When purchasing lighting, it's important to understand the differences between various light sources and the terminology included on the packaging. The right bulbs could not only lower your electric bill, but impact flock performance. And the light you choose will depend on whether you are rearing broilers, pullets or hens. The key selection criteria includes the type of bulb, its wattage, lumen output or intensity, lumen/watt ratio, temperature (°K), cost, lifespan and warranty. Bulb type The driving force behind advances in lighting technology is energy conservation. 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. 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. 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 bulbs 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 sidewall housing is common, new hen houses (12 m width) are being equipped with two rows of 18 watt LED tube lighting with 4-meter spacing. Light intensity It's important to recognize that broilers, pullets and hens have different lighting requirements when it comes to intensity. Light output, or lumens, can be measured with a light meter but not all light meters have the same sensitivity. It's important to use the correct light meter 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 and 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 vice versa. Typical bulb spacing is usually around 20 ft (6.5 m) centers; 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). Lumen depreciation 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, excessive dust and dirt accumulation can potentially reduce luminosity from 10-20%. Minimize this 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. Color, temperature and wavelength 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 color/ temperature (°K) is the lower the temperature, the longer the wavelength. Color, 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 color wavelengths although with a slight tilt toward red and infrared making it the perfect light for photo stimulation. Light bulbs in the 2,200-2,700°K range are manufactured to mimic natural sunlight as closely as possible. Cobb recommends using bulbs with 2,700°K or less in hen houses to stimulate egg production, while broiler houses typically use bulbs rated between 3,000-5,000°K. Light frequencies can be read with a Spectrora diameter. Economics 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) centers, 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). Bulb of choice 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. 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 decreased wattage draw, greater lifespan, warranties and in some instances rebate programs. The one note of caution when using 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.