For groups of pigs to cope adequately with their housing conditions they need sufficient
static space (occupied by the body of the pig), activity space (for movement between different
functional areas and behaviours relating to these) and interaction space (for appropriate
social behaviour). Estimates for static space have been presented for thermoneutral conditions,
but are expected to increase substantially as temperature increases. The present paper
models the relationship between ambient temperatures above the comfort zone, and thermoregulatory
lying behaviour in finishing pigs. Estimates of the effect of posture on floor
occupation were obtained and presented as ‘k-values’ (k = floor area occupied (m2)/body
weight2/3 (kg)) to correct for the effect of pig size. A literature review was conducted to collect
information on three aspects of lying behaviour: lying frequency, posture (lateral, semi
lateral or ventral lying) and level of space sharing (huddling) in response to increasing temperatures.
The lowest and highest values found were: increase in lying down: 0.2–0.66%,
reduction in space sharing: 1.7–4.9% and increase in lateral vs sternal lying: 0.8–2.3% per ◦C
temperature increase. Extrapolation of k values in the comfort zone to T = 31 ◦C suggests a
range of k-values from k = 0.0331 to k = 0.0385 for static space. In the second part of this
paper we analyse video data from a pig building in which groups of 18 pigs were kept in
large pens (1.67 m2 per animal) at temperatures ranging from 16 to 32 ◦C. We find a value
of k = 0.0339 at T = 31 ◦C for static space, which is at the lower end of the range predicted
from literature. A possible explanation for this relatively low additional space requirement
is that the animals coped by increasingly using the slatted area (with sprinkler system) as
a lying area. The study confirms earlier suggestions that the amount of space required by
EU legislation is insufficient for pigs at the end of the finishing period, even at relatively
low temperatures. In situations where the average room temperature exceeds the comfort
zone, pigs need additional space to cope with their housing system, or alternative methods
to cool themselves down.