Automatic weighing of individual laying hens in aviary housing systems

1. This study investigated when and where body weight and flock-uniformity should be determined in an aviary system by using automatic weighing systems. 2. An Individual Poultry Weighing System (IPWS) was developed to record time, duration, location and body weight of visits of individual hens to 4 weighing scales. 3. The number of hens that visited the weighing scales per 3 h period varied from less than 10 during the dark-period to more than 60 during the light-period. 4. The average number of visits per individual hen was 1.4 and the average number of successful weighings per hen was 0.6 during the light-period. 5. Body weight showed a diurnal rhythm: the difference between the maximum body weight at night and the minimum body weight in the morning was 63 g. 6. The location of the scales influenced number of visits, number of weighings, mean body weight, flock-uniformity and duration of visits. 7. Body weight per 3 h period did not differ between hens which were individually recognised and those which were not. 8. Flock-uniformity was 2.6% higher during the light-period if it was based on weighings of identified hen visits. 9. The average duration of the visits to the scales in the middle of the feeding tier during the light-period was 63 s. 10. Of all the hens that visited the scales during a 24 h period, 54% visited them only once. 11. Automatic weighing systems without individual hen recognition can deliver reliable management information on mean body weight and flock-uniformity in aviary systems if the weighing scales are located on the feeding tier in the middle of the house and if they are used during the light-period.