Beat the Heat : Reducing heat stress through floor cooling: effects on the indoor environment, hygiene, and behaviour in a commercial growing–finishing pig barn

Abstract

Climate changes are creating substantial future challenges in modern pig housing. This is due to more frequent, longer, and more intense heat waves. Even under present housing conditions, pigs in temperate climates are subject to heat stress, compromising welfare, health, and production with potential negative consequences for morbidity, mortality, and economic performance. Growingfinishing pigs have well-known morphological and physiological limitations in dissipating metabolic heat, making them particularly sensitive to warm housing conditions. This Licentiate thesis investigated floor cooling in partly slatted pens for growing-finishing pigs during warm conditions, evaluating its effects on the thermal and gaseous environment, hygiene, and behavioural indicators of heat load. The study was conducted during two consecutive summers (2022 and 2023) in two pig units on a commercial farm and included approximately 1400 growing-finishing pigs. A crossover design was used, with one unit cooled and the parallel unit serving as the control. Floor cooling was implemented by connecting a cooling unit to an existing water-based floor heating system embedded in the floor of the lying area. The results show that floor cooling reduced the temperature of the lying floor, the slatted dunging floor, and the ambient air at unit level. Additionally, ammonia and carbon dioxide concentrations were decreased, and pen and pig hygiene were improved. Pig behaviour was recorded weekly over 24 h and assessed across four observation periods per day. The behavioural observations showed that floor cooling increased the proportion of pigs occupying the lying area and decreased the proportion occupying the dunging area. The effect varied with observation period, with significant differences during the morning, evening, and night, but not at noon. Floor cooling increased the proportion of pigs lying in the lying area and adopting a lateral lying posture. Although standing and sitting occurred only to a limited extent, floor cooling reduced standing in the dunging area and sitting in both pen areas. Overall, floor cooling improved the thermal and gaseous environment, enhanced pen and pig hygiene and promoted behavioural thermoregulation. Floor cooling was successfully implemented in a commercial growing-finishing pig barn, and the findings demonstrate that the measure is a practical strategy for beating the heat in commercial growing finishing pig production.