The field trial was conducted in a commercial farm with 72 sows from DanBred(r) genetics and aimed to evaluate the effects of the evaporative cooling and electrolyte balance on the performance and thermoregulatory parameters of lactating sows during summer. The experimental design was randomized blocks with four treatments in a factorial arrangement 2 x 2 and 18 replicates per treatment. Treatments were two ventilation systems (natural ventilation or evaporative cooling) and two diets (electrolyte balance of 175mEqkg-1 or high electrolyte balance of 275mEqkg-1). The average values for temperature and relative humidity were 24.8°C and 64.5%, respectively, being obtained daily values of 31.6°C for the maximum temperature and of 19.8°C for the minimum temperature. There was no effect (P>0.05) of evaporative cooling and electrolyte balance on feed intake, body condition and weaning-to-estrus interval of sows. The evaporative cooling caused a significant reduction (P<0.05) in respiratory rate and surface temperature measurements in the morning and afternoon and evening rectal temperature and increase (P<0.1) in the weight of piglets at weaning. The dietary high electrolyte balance did not change these variables. It was concluded that the use of the evaporative cooling system helped to reduce the effects of heat on the variables related to body thermoregulation during the summer and provided an increase in weaning piglet weight. The utilization of a diet with specific nutrient levels for hot climates, the high electrolyte balance did not reduce the effects of heat stress in sows.
performance; diet; pigs; thermoregulation; ventilation
