Consistency of Measurement of Social Status in Dry-sows Group-Housed in Indoor and Outdoor Systems
Each of two 20-sow groups consisted of gilts ie virgin sows (one third) and sows (parity 2–5, ie sows which had given birth 2–5 times). One group was housed indoors with a straw-covered lying area and dunging area. Another group was housed outdoors with a covered straw lying
area and two rooting fields. Behavioural observations were made on both groups: indoor sows were observed for 4h day−1, for 10 days (40h); outdoor sows were observed for 6h day−1, for 21 days (l26h). Social interactions were classified as threat, bite, knock
and push. Continuous data on the type of interaction and the winner or loser were recorded. Four measures of social status, based on social behaviour, were calculated: i) displacement index; ii) level of interaction; iii) success in interactions; and iv) matrix dominance. Spearman rank correlation
coefficients between different ranked measures of social status within each group (outdoor or indoor) were significant for displacement index, success in interaction and matrix dominance. The level of interaction did not correlate with other measures (except for matrix dominance in the indoor
group). Measures of displacement, success in interaction and matrix dominance provide highly consistent and correlated measures of social status.