Among the many arguments to oppose the activists’ attacks on professional poultry farming that we address with M.A.C., the time has come to deal with the management of lighting in poultry farms, which is another topic often used instrumentally by those who, rejecting a scientific approach, describe intensively protected farms as places of torture.
The influence of light on animal welfare cannot be defined with the same criteria that we apply to people.
What counts is intensity, frequency, gradualness and above all knowing how much and how it affects animal welfare. In fact, it is no coincidence that light management is one of the many attentions the industry pays to the animals it breeds. It has now been scientifically verified that, although it is intangible, light has an important impact on poultry welfare.
By studying the relationship that chickens and hens have with light, it was found that light sources are perceived very differently by them than by us humans. This is because the structure of our eye is very different from that of a chicken. This alone explains why judging the lighting of a farm is a subject that can only be addressed by trained and experienced people and not by those who often wear blinders and sunglasses.
Why do chickens and laying hens need light?
Let us try to answer in the simplest way that nevertheless stems from precise findings that guide animal welfare.
Egg production for laying hens is guided by the hours of light.
The length of the day is important. Lighting programmes and light colour influence reproduction, but only in the sense that they are designed and applied so that the light is pleasant and the dark/light alternation is constant and not as variable as it is in different seasons and geographical areas.
Both chickens and laying hens also need light to express their behaviour. Light stimulates them, makes them active, helps them to orient themselves in the space they inhabit, to find nests, food and water.
Curiosity: chickens know that they are prey, an awareness contained in their DNA, an atavistic condition that has allowed them to develop a special capacity for vision: they see in every direction, at all times and can control what they eat with one eye and the environment with the other.
Light also creates shade, which is managed on farms. In fact, laying hens seek shade to hide, rest and lay their eggs. They need to feel comfortable and safe in the nests.
For the same reason, light is also managed to prevent shading where it is least appropriate, to prevent ‘unintentional’ areas of shade from causing eggs to be laid outside the nests.
How do chickens and laying hens see the light?
Chickens and laying hens see a wider portion of the electromagnetic spectrum than we do. They can see UV-A radiation, which is therefore visible light to them. They are also more sensitive to red and blue light and also perceive light through their skin and skull, which influences their biorhythm and sexual development.
The bright area in the graph below shows what humans can see. The darker area, both to the right and left of what is shown as visible to humans, is the part of the electromagnetic spectrum visible to chickens and laying hens and serves to explain to the more sceptical why the vision of chickens and laying hens is different from that of humans, as well as to give further confirmation that assessing the quality of light by non-experts can be “rather difficult”.
Returning to light in the strict sense and how the knowledge developed on this subject has given rise to special care for chickens and laying hens, it has been internationally established that on farms the legal minimum hours of darkness must be 6 hours for broilers and 8 hours for laying hens, all controlled by automatic clocks or computers. After the 6 hours of sleep for chickens and 8 hours for laying hens, the lights come on and a new day begins. This is why from midnight onwards you can already see sheds with lights on, which is unfortunately often used to make people believe that chickens and hens are kept in 24-hour light.
In sheds with windows, farmers exploit the natural decline in light at dusk and the increasing dimness in the shed to encourage the animals to prepare for the night. In sheds without windows, dusk is simulated by special dimmers. This ritual allows the animals to get used to a condition that is predictable for them and therefore does not cause them stress (of light) and to go to their favourite place to prepare for sleep. In the dark, chickens and laying hens immediately start sleeping. The inside of the sheds is made dark already around 6 p.m. in winter and 10 p.m. in summer.
What kind of light should be used in animal husbandry to ensure the ‘luminous’ well-being of animals?
Birds in the eyes have 85% cones and 15% rods; humans have 5% cones and 95% rods. This is why chickens can already recognise colour at a light intensity of 8 lux while people start to recognise colour at 20 lux.
Chickens see more than we humans do. When it is almost dark for us there is still light for them. So when it comes to light intensity for chickens, experts express themselves using not the Lux, but the Gallilux, which is the unit of measurement of light intensity based on the spectral sensitivity of chickens. For convenience in this article we will continue to use Lux.
Let us now summarise the most important issues on light in poultry farming by adding a few details
Regular laying of eggs is linked to the hens’ regular exposure to light. Light stimulates the pituitary gland to secrete the hormones necessary for laying and it is therefore important that the duration of light is constant and (like room temperature) also appropriate to the animal’s age. In general, daily light exposure gradually increases (one hour per week) from 8-10 hours (when the animal is 16 weeks old) to 16 hours from 22-23 weeks onwards.
If the farm is permeable to natural light (as this varies over the course of the year also in relation to the geographical location of the farm), periods of artificial light are provided in the morning before the start of daylight and in the evening before darkness, so that the total duration of illumination per day is always equal and constant.
Now for a little technicality: the minimum light intensity on farms according to EU animal welfare regulations is 5-10 lux. However, it is widespread good practice to keep an intensity of 25-30 lux which allows farmers a proper inspection of animals and equipment.
The definition of darkness in a farm may also be of some interest: the dark phase, which for convenience is called night, must have a light level of less than 0.5 lux for it to be considered as such.
The intensity of the light periods and the lack thereof must be uniform in the area frequented by the hens. For this reason, the lamps are positioned in the hen house so that there are no dark or excessively lit areas.
The care to be taken to avoid shady areas where it is not appropriate stems from the fact that laying hens, by their very nature, seek out dark places to lay their eggs, so shady areas must be kept to a minimum as the hens must be prevented from laying their eggs outside their nests.
The editorial staff of M.A.C.
