Warm white light and flicker free power key to calmer flocks, Hato tells Armagh conference

Published on : 30 Sep 2026

Max Obers, chief executive of Hato Lighting

Laying hens reared under warm white light of around 3,000 Kelvin are calmer and less prone to aggressive behaviour and feather pecking than birds reared under cold white light, Max Obers, chief executive of Hato Lighting, told the Parklands Poultry Conference in Armagh on Tuesday (29 September).

Mr Obers said the company employs 220 people and works solely on improving the welfare and performance of animals through lighting, and that over five decades it had learned how to change the behaviour of poultry "within seconds" in producers' sheds.

How birds see light
He said poultry perceive light differently from humans. People have three types of cone in the eye, which pick up blue, green and red, whilst poultry have more cones and can also see ultraviolet light, so the spectrum a chicken perceives is wider and birds see in far more colour than we do. Birds also take in light through the brain as well as the eyes. When light intensity is above 4 lux, the red part of the spectrum in particular penetrates the skull and is absorbed by the hypothalamus and the pineal gland, which means light can still influence a bird that is completely blind.

Mr Obers said Hato had identified eight aspects of light that matter in a poultry house, all of which can be measured on farm, and he covered three of them: spectrum, colour, and flicker.

Spectrum and colour temperature
He said some farmers use a single colour, only white, only blue, or only green or red, and that this will never benefit the overall performance of the flock. "The closer your light will be to the sunlight outside, so the wider the spectrum is, the better it will be for the performance of your flock and development of the birds overall," he said.

LED lights can be built to produce any spectrum, and a full spectrum is seen as white light. Colour temperature is measured in Kelvin, with the warmer white of sunrise at around 3,000 Kelvin and the colder white of midday sun at around 5,000 Kelvin. Mr Obers said the warmer the light, the calmer the hens will be, and the higher the Kelvin, the more active they become. With lights that can switch between warm and cold white, farmers will see activity rise within seconds of making the change.

Where a producer can choose only one setting, Mr Obers said 3,000 Kelvin warm white performs best overall for laying hens and rearing. Some rearers use cold white light at the start of the growing period because it stimulates activity and muscle development in pullets, but he said tests in the Netherlands over the last decade had shown that pullets reared under cold white light were more active once they reached the laying farm and had more problems with aggressive behaviour and pecking. For that reason most of the facilities Hato supplies that choose a single light go for warm white. If the infrastructure allows both, he said it is beneficial to start pullets on a colder white light and then move to warm white for the rest of rearing.

Red and blue light
Mr Obers said red light is a useful tool in laying flocks. When aggressive behaviour or pecking breaks out, keeping the white light on and mixing in extra red will stop it immediately. "Ideally, you never need it, but once it happens, it's nice to have it," he said. Once the flock has settled, a few hours or a day later, the red should be taken out again and the normal lighting programme resumed.

Monochromatic blue light, with all the red removed, makes birds freeze and sit still, which he said is useful for handling, vaccinating, and populating or depopulating the house. He said it is a common assumption that birds stop moving because they cannot see blue light, but that they see it very well. Lux is calculated on the spectrum humans can see, whilst gallilux takes in the full range poultry perceive, and blue light measured at 3.79 lux registers 34.5 gallilux. Why birds sit still under blue light has not been scientifically proven, he said, but it is thought to simulate a clear night with a full moon, when birds keep still for fear of predators. "It's not scientifically proven, but it works very well within your facility," he said. He showed a video of broilers being caught first under warm white light and then two minutes later under blue light, and said it works the same way for laying hens.

Flicker
Mr Obers said standard lights running on 230 volt AC switch on and off very rapidly. Humans cannot see this, but poultry can, and because they also perceive light through the brain Hato has seen more stress and poorer performance in flocks lit this way. Most of the systems Hato supplies run on 48 volt DC to give a stable light. With a measuring tool, a flicker index below 0.06 and a flicker percentage below 10 can be considered completely flicker free. Without one, he said farmers can dim their lights right down and film them in slow motion on a smartphone, and if the lights are seen going on and off there is too much flicker in the house.

Training birds into the system
Mr Obers also explained how lighting can train birds to go into the system at night. He advised installing lights in several dimming groups, four in a multi-tier house, and at the end of the day dimming the under-system lights first, then the aisle lines, then the in-system lines and finally any perch lines above the system, over about 15 minutes. In a flat-deck house the inside and outside lines can be put on separate dimming groups to the same effect.

A video shown during the talk demonstrated Hato's Corax main lighting and Bubo system lighting being dimmed in sequence, with birds that had learned the behaviour in the rearing shed responding in exactly the same way in the laying shed. Mr Obers said Hato has tools to measure all eight aspects of light and offered to follow up with producers through webinars and discussions.