- Department of Animal Environment and Health, Swedish University of Agricultural Sciences
Previous research on the effect of stocking density on welfare has focused on adverse effects on health and behaviour. Absence of such effects does not mean that space allowance is optimal from the animals’ point of view. This thesis aimed to assess optimal space allowances by studying spatial distribution and behaviour. The importance of lower densities was studied using a combination of preference and motivation testing. Broilers were increasingly attracted to the pen walls as stocking density increased. This attraction seems to stem from an attempt to minimize disturbances by conspecifics, which increased with stocking density (paper I). Such environmental influences on spacing need to be corrected for when studying the social component of spatial distribution: attraction/avoidance between animals. When such corrections were made, broilers were found to avoid each other if stocked at densities above 2.4 birds/m² (paper II). Broiler chickens showed a considerable motivation for densities below 15 birds/m2. To get to lower densities, they crossed barriers that deterred 20-25% of broilers from obtaining feed after 6 hours of feed deprivation (paper III). When environmental influences were accounted for, fattening rabbits avoided their conspecifics at all densities studied, suggesting that the optimal stocking density lies below 5 animals/m² in this species. Furthermore, they seemed less attracted to each other when a wooden enrichment structure was present (paper IV). Fattening rabbits spent more time lying sternally at higher densities, possibly because other behaviours were increasingly impeded. In enriched cages less time was spent on cage manipulation, social contact and drinking. This time was instead spent gnawing and exploring the structure, suggesting that in barren cages such behaviour was redirected towards conspecifics and cage materials (paper V). The results show the importance of correcting for environmental influences when assessing the social component of spatial distribution. Additionally, the use of multiple distribution indices is recommended.
broiler chickens; rabbits; stocking density; group size; cages; density; spatial distribution; behaviour
Acta Universitatis Agriculturae Sueciae
2011, number: 2011:8
Publisher: Department of Animal Environment and Health, Swedish University of Agricultural Sciences
Animal and Dairy Science
Behavioral Sciences Biology