The allocation of space allowance treatments within each room (see below) ensured that there were few differences between rooms in average stocking density. Both farms had water sprinklers for hot weather (activated when the outdoor temperature was above 12 °C), located over the slatted part of the pen. Sprinklers came on for 45 s every 30 min between 0800 h and 2000 h. Farm B had air heaters for cold weather.
PRRS were present on both farms and probably also PMWS at Farm B. There were no outbreaks of clinical disease, but the causative agent which is thought to be porcine circovirus type 2 (PCV2) was present (Danish Veterinary Laboratory, Copenhagen).