Cooling effect of water pad-fan system for fattening pig houses in Beijing

Abstract: High temperature in summer will cause serious impact on the production performance of pigs. So it is very important to control temperature in the pig houses in Beijing, China. An experiment was conducted to compare the cooling effect of the water pad-fan and only fan in pig house in Beijing from July 24th to August 11th, 2015. Before testing the cooling effect, a manual test system for measuring fan ventilation rate was designed and applied to check if the ventilation rate of the experimental pig houses was appropriate. The water pad-area for the experimental pig house was checked too. A total of 188 finishing pigs (each pig 100-110 kg) were prepared for the experiment and divided into 2 pig houses averagely. Temperature and relative humidity outside the pig houses and temperature, relative humidity and wind speed at 6 sections in the pig houses were monitored. The results showed that the ventilation rate and water pad-area were up to the standard recommended by "Midwest Plan Service Structures and Environment Handbook". During the experimental period, the wind speed range at Section 1-6 in the water pad-fan pig house and the fan pig house was 0.51-0.84 and 0.51-0.68 m/s, respectively. There was insignificant difference between the water pad-fan pig house and the fan pig house for whole wind speed (P>0.05). The water pad-fan system could reduce the temperature inside the pig house by 12.3 ℃ at most compared to the temperature outside while the fan system could reduce the temperature inside the pig house by 7.6 ℃ compared to the temperature outside in the same experimental period. But when the temperature and relative humidity outside the pig houses were 36.5 ℃ and 60.1%, respectively, the water pad-fan system could not control the temperature inside the pig house below 31.7 ℃. During the 450 h experimental period, the time percentage for the water pad-fan pig house and fan pig house with indoor temperature of below 28.0 ℃ was 71.6% and 61.8%, respectively, and that above 30.0 ℃ was 5.0% and 20.2%, respectively. The temperature at Section 1 was 0.4-2.2 ℃ lower than that at Section 6 in the water pad-fan pig house while the temperature difference at different sections in the fan pig house was not significant (P>0.05). The relative humidity difference at different sections both in the water pad-fan pig house and in the fan pig house was not significant (P>0.05). Respiration rates in the water pad-fan pig house were reduced by 3.82 bpm (breaths per minute) at 12:00 and 3.05 bpm at 14:00 compared to those in the fan pig house (P<0.05), and respiration rate was affected by temperature (P<0.05). Being one kind of evaporative cooling method, the water pad-fan system would consume 1.20-6.27 m3 water per day during the days with good cooling effect and the temperature was reduced by 4.0-12.3 ℃ compared to the temperature outside the pig houses. The temperature range reduced was not consistent with the water consumption at all time because the relative humidity was not the same in different days. These results indicate that the water pad-fan cooling system is better than the fan cooling system in pig houses in Beijing, China.