[Measurement of floor space allowance of Lohmann Silver hens using biometric data]

Space allowance for laying hens is one of the most disputed criteria of modern laying hen husbandry. Fast and cheap methods to achieve reliable data about the space occupied by laying hens are missing. This studie is based on a method, that can be used to measure the space ocupied by laying hens using digital images from above. 100 hens were photographed digitally when walking or scratching freely on a blue coloured wooden plate that had been placed in a sheltered outdoor scratching area. The birds were 65 weeks old and in the 47th laying week. The body width and the floor area covered by the hens were measured from the photographs by the KobaPlan color contrast planimetric method using a personal computer. Another 50 hens were randomly caught and weighed in order to get an estimate of the average bird weight of the herd. The mean floor space covered by the hens was 545.4 cm2 (SD: +/- 51.9) and their mean width was 173.9 mm (SD: +/- 8.9). The mean weight of the 50 hens was 2085.8 g (SD: +/- 234.0 g). Compared to the space allowance in the German "Kleingruppenhaltung" (small colony cage holdings) Lohman Silver laying hens occupy more than half (68.2% resp. 60.6%) of the minimum floor space of 800 cm2 per hen resp. 900 cm2 for hens heavier than 2 kg (Nutztierhaltungsverordnung 2006). Subsequently less than half of the floor space (32.6% resp. 39.8%) can be used for movement or other normal behaviours including social behaviour. Compared to the floor space of 750 cm2 per hen as laid down in the European Council Directive 1999/74/EC, 72.5% of the floor space in furnished cages is covered by the birds. Further data on the floor space covered by the body size of layers in different situations and from different genetic strains can be gained using the KoBaPlan method in order to estimate reasonable space allowances for laying hens in modern husbandry systems which in particular should enable the hens to perform normal behaviour. This is evenly important for hens which start laying with less than 2 kg but exceed 2 kg while in production as given in the German regulation.