Biometric measurement of static space required by weaned piglets kept in groups of eight during 6 weeks

Adequate space allocation is deemed to be an important criterion for animal welfare in modern pig farming. However, it is not a simple matter to determine how much space a group of pigs needs, and precise, animal-based data about the floor area needed by the body dimensions of group-housed pigs in different weight categories are currently lacking. So as to collect biometric data on the static space of weaned pigs kept in groups and to evaluate current spatial requirements, an automatic measurement of the floor area covered by the pigs’ bodies within groups was performed. Consequently, the resulting free space in a pen, available for (non-) locomotor behaviours, was calculated. In three batches, two groups of eight piglets each were formed after weaning. Using three-dimensional cameras that recorded a piglets’ pen from top view and a software for image analysis, the exact static space of a group considering different body positions was measured and specified in square centimetres. Measurements were taken weekly for a total period of 6 weeks per batch. The area covered by the bodies of a group of eight piglets increased almost linearly with increasing average bodyweight (R 2 = 0.99, n = 1645 images). The highest mean static space was measured in Week 6 (1.54 m2, average bodyweight: 25.2 kg) when 100% of piglets were lying with less than 50% huddling. When 100% of piglets within a group were lying, more than 50% huddling reduced the mean static space to 1.4 m2 (P < 0.05). When all pigs of a group were lying, significantly more space was covered than in situations when all pigs of a group were standing (1.54 m2 vs 1.36 m2, P < 0.05). Exclusively in Week 1, when piglets were lying with more than 50% huddling, the space covered by the group was slightly reduced compared with the situation when 100% of piglets were standing. By the automatic method, realistic results on the static space of piglets kept in groups were achieved. Space requirements of the largest animals in the most space-demanding body positions should be the basis for space recommendations for nursery pigs.