Hens that are kept under free range conditions automatically have more freedom of movement. Those birds that use their freedom abundantly tend to lay less eggs however. Breeding therefore should focus on responding to this behaviour.
By Wiebke Icken , and Dr. Rudolf Preisinger, Lohmann Tierzucht, Cuxhaven, Germany
With the aid of a new transponder technology, the free-range behaviour and laying performance of layers can be tested simultaneously. Lohmann Tierzucht, together with the Bavarian State Research Centre in Germany, investigated the laying behaviour of 272 Lohmann Silver hens in Electronic Pop Holes (EPH) and Funnel Nest Boxes (FNB).
These systems made it possible to record automatically each separate visit to the free-range area as well as the egg number by every single hen in the flock. The hens were housed in an aviary with an adjoining winter garden at the Thalhausen experimental station of the Technical University of Munich. To identify each single hen in the EPH and FNB, every hen was tagged with a transponder on one leg. During the whole investigation period of one year, the winter garden was continuously accessible for the hens.
The frequency of passages (number of passages between the in- and the outside area) and the duration of stay in the free-range area of each hen was recorded daily. A large fraction of the hens (35%), did not use the winter garden at all. They were not even once registered at one of the four EPH throughout the whole year. The percentage of hens that used the winter garden (at least once in a 28 day period), increased during the observation period. As soon as a hen was familiar with the winter garden, she visited the free-range area nearly every day. Expected effects, like a reduction of the share during autumn and winter, were not found.
The highest number of passages through the EPH was registered in the second laying period (15 passages per hen per day). Thereafter, the frequency decreased from a level of 13 passages in the fifth laying period to eight passages in the 12th laying period. The average length of stay in the winter garden showed an antagonistic trend to the frequency of passages. At the beginning of the observation period, the average visit to the winter garden had a duration of 14 minutes, whereas from laying period seven to the end of the observation, a single stay took an average of more than 30 minutes.
The number of passages and the duration of stay in the winter garden showed a big variation from hen to hen. There were some hens which returned to the barn after a short glance into the winter garden, whereas others stayed nearly day and night outside. Most of the passages through the EPH were registered in the morning between 6 am and 8 am as well as in the afternoon between 4 pm and 5 pm. The average stay in the winter garden per hen per day was about 2.5 to 4 hours. At four o’clock in the morning, the artificial light in the barn was switched on and at 8 pm, it was switched off. From 8 am onwards, the hens were looking intensively for the FNB to lay their eggs. The laying performance of the hens were calculated for each 28-day laying period, beginning with the first correct registered egg in the FNB.
A bacteria infection in the third laying period caused the very late peak of the laying performance (94,2%) in the sixth laying period. The laying performance stayed on a slightly lower level thereafter, with a drop to 86% during the 12th laying period. The estimated heritabilities for the egg number were generally at a low level, varying from one laying period to the next.
Positive and negative correlation
Genetic and phenotypic correlations were estimated for the traits: frequency of passages, length of stay in the winter garden and laying performance. A highly positive correlation between the frequency of passages and the length of stay were expected and validated by the close relationship between both traits. Negative genetic correlations were estimated between both parameters for the ranging behaviour and the laying performance. Only a slightly negative trend could be found in the correlation between the traits: frequency of passages and laying performance, whereas a moderate negative correlation was detected between the traits: length of stay in the winter garden and laying performance.
Until now, no literature could be found which describe the correlations between the two free range parameters (frequency of passages and length of stay) and the laying performance, like in this investigation. Therefore, the EPH and FNB first showed the possibility to simultaneously record the free-range behaviour and egg number for each hen in a group housing system, with a justifiable effort under field conditions. It is being reviewed, how the recorded data can be integrated into the current breeding programme to improve and sustain the nest and free-range acceptance.
To conclude, it can be said that layers do have a constant free-range behaviour pattern throughout the day. After getting familiar with the new production environment, many hens pay their first visit to the outside area nearly two hours after the lights were turned on. About half an hour later, they went back to the barn to lay their eggs and meet other needs such as feed and water consumption.
During the whole day, layers switch between in-and outdoors several times. Variation in free-range activity from hen to hen showed that hens with a high passage frequency tend to lay less eggs than hens with only two to three passages per day. However, about 35% of the hens do not go out. This is probably due to their fear of exploring a new environment and not due to laziness. It is not important for them to have a high free-range activity, but rather in the production system visiting nest boxes for laying purposes.