Potential for evaporative cooling during heat stress periods in pig production in Portugal (Alentejo)

Hot weather adversely affects the performance of pig production. Under heat stress, penalties to efficient performance, production, reproduction, feed conversion, health and welfare of animals can be severe. In the Alentejo r egion of Portugal, the main losses in pig production result from the summer dry period, characterized by high air temperature and low relative humidit y. For this study, hourly air temperature and relative humidity data from four meteorological stations in the Alentejo were analysed for the period 1995- 1997. Relationships between temperature and relative humidity have been est ablished. Temperature-humidity indices (THI) given by several authors were computed and compared between the meteorological stations. The indices perm itted the determination of the heat stress periods during summer. The significant duration and intensity of the heat stress periods associate d with the high losses in pig production justify the research of a cost-eff ective way of overcoming the problem. The frequent occurrence of both high temperature and low relative humidity during the heat stress periods is an indication that evaporative cooling systems may be a feasible and cost-effe ctive solution for minimizing high thermal stressors in pig production. A c omputer simulation using the psychrometric equations predicted that most pe riods of heat stress occurring frequently during the summer could be elimin ated by using an evaporative cooling system with an efficiency of 80%. (C) 2000 Silsoe Research Institute.