Investigating the effect of pen shape and pen size on group flight distance of extensively managed ewes

Abstract

This study investigated the effect of pen shape and pen size on the group flight distance of extensively managed ewes, and how flight distances of individual ewes compared when recorded in group and isolated settings. Within eight groups of 25 sheep, six focal animals were randomly selected (N = 48 ewes). Over four days, groups were placed in four different sized and shaped pens and flight distances (m) of focal animals were recorded. Pens designs were small rectangle (3.3 m x 7.2 m), medium rectangle (4.8 m x 5.8 m), large rectangle (11 m x 19.6 m) and curved/concave (with 31.5 m perimeter). Following a previously validated protocol, flight distance (m) was also recorded when focal sheep were physically isolated from conspecifics. There was no association between the isolated flight distance and group flight distance of focal animals (n = 39, r(37) = 0.03, P = 0.83).Group flight distance was significantly affected by pen design (P < 0.001), being greater in large pens and smaller in small pens. To account for these pen effects, group flight distance was adjusted and analysed as a proportion of the largest dimension of each pen. To test this mathematical adjustment, pen and other variables predicted to have an influence on adjusted group flight distance were analysed as fixed effects in linear mixed models. A statistically significant Day x Pen interaction was found (F9,84 = 3.01, P < 0.004), although post-hoc pairwise comparisons showed that this interaction had no clear pattern across days or pens. The simple mathematical adjustment and statistical modelling made group flight distances comparable by accounting for day and pen effects. These results suggest that analysing group flight distance as a proportion of the pen in future welfare assessments will enable comparisons to be made between sites.