After the rearing period, broiler breeders receive extra light to give a stimulus for egg production. This normally is done at an age of approximately 20-21 weeks, depending on the development of the flock, the body weight etc. The light stimulus normally consists of two variables, day length and light intensity. Depending on the program, the day length increases in weekly steps from 8 hours to 11 hours and then to 12, 13 and eventually 14 hours. In the same period, the light intensity is also increased, from 2-5 lux with weekly steps of 5-15 lux to eventually 60-80 lux. With a normal developed flock we see that approximately 9-10 days after the first light stimulation we have the first eggs, and another 9-10 days later we have 5% production. This means that if we start the light stimulation at 147 days, we can expect the first eggs around 157 days, and 5% production at 167 days.

We usually do not want to increase the light intensity too quick, because over-stimulation of the reproductive system can lead to more issues with double yolks but also prolapse, peritonitis, pecking, aggressive behavior of the males etc.

However, a slow increase of the light intensity has a down side. When a bird feels the hormonal changes that lead to the production of the first egg, it will start looking for a nest. This is not done at the moment of producing the egg, because in nature it takes time to find a good spot for a nest, to bring bedding material to that nest, to line the nest with that material etc. This means that in accordance with the instinct of a bird, it will start to look for a good place for a nest already a week or even longer before that first egg is produced. The fact that in our production system there are suitable nests available in the houses doesn’t really change that instinctive behavior. This is not only the case in birds, for instance also women show “nesting” behavior before the baby is born, an instinct to make the environment ready for the newborn, although she knows very well that everything is ready already for weeks.

But in our chicken house it means that the first birds start to look for a good place to nest shortly after the light stimulation is given. As the birds reach 0.1% production at 157 days and 5%  production is reached at 167 days, a fraction of the birds is looking for the nests in the period from 150 days onwards, or shortly after the first light stimulation.

But for a bird, everything can be a nest, as long as it is comfortable, safe, protected, cosy etc. So when the light intensity is still at a low level, the litter is quite attractive for the birds to nest. This means that the first birds have more change to produce floor eggs, because when those birds are choosing their nests the light intensity is still low and the litter is relatively dark. We actually can see that in the field, as the floor egg percentage is going down when the production is increasing. This is not because the birds that are coming in production later are more intelligent to recognize our nests for what it is, but because the litter is becoming less attractive due to the increasing light intensity.

This means that for production and mortality it might be more safe to keep the light on a low intensity at the start, as light duration will bring the birds in production anyway, but for floor eggs we want to increase the light intensity more quickly.

The fastest increase will not be equal for every flock and every breed, but be aware that a slow increase might create more floor eggs.