With increasing global temperatures, the risk of heat stress for farm animals is growing. As pigs are not able to sweat and in livestock houses they generally do not have the opportunity to wet themselves, an ambient temperature above the upper critical temperature (UCT) leads to reduced welfare and performance.
In the “Review on cooling technologies for pigs” technologies are described on cooling pigs kept on farms. This includes cooling of pigs, e.g. by sprinklers/showers, floor cooling, and fans for air circulation. Techniques also include those on cooling the environment, e.g. by heat exchangers, fog/mist, cooling pads, air conditioner, underground tubes, and underfloor air inlets. The knowledge in this review aims to support welfare inspectors in the field of climate control on pig farms, in particular at high temperatures.
Validity
Although temperature differences between countries during summer are large, the information and recommendations are valid for all European pig farms. There are not many legal requirements included in the respective EU Welfare Directives on indoor climate in pig houses, although some countries have more detailed rules. This implicates that inspectors need both animal based and environment based indicators to assess whether pigs experience heat stress and to enforce these open formulated legislative requirements by applying cooling technologies.
Upper critical temperature
Theoretically, heat stress starts when the ambient temperature exceeds the upper critical temperature of the thermoneutral zone. Above this temperature, pigs will actively increase heat loss to maintain their core body temperature. It should be noted that also between the upper limit of the comfort zone and upper critical temperature pigs already make adaptations to increase heat loss, but these changes do not affect heat production.
Active changes in pigs to increase heat loss are physiological, e.g., an increase in respiration rate. They may also include behavioural adaptations, e.g., lying on slatted floor instead of on an insulated solid floor. The upper critical temperature depends on age (body weight) and stage of production: when it is not exceeded it is both beneficial for animal welfare as for profitability.
Introphoto: (©WUR)