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 region of Portugal, the main losses in pig production result from the summer dry period, characterized by high air temperature and low relative humidity. 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 established. Temperature-humidity indices (THI) given by several authors were computed and compared between the meteorological stations. The indices permitted the determination of the heat stress periods during summer. The significant duration and intensity of the heat stress periods associated with the high losses in pig production justify the research of a cost-effective 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-effective solution for minimizing high thermal stressors in pig production. A computer simulation using the psychrometric equations predicted that most periods of heat stress occurring frequently during the summer could be eliminated by using an evaporative cooling system with an efficiency of 80%. (C) 2000 Silsoe Research Institute.