In discussions of summer cooling in pig barns, people often jump straight to “install cooling pads” or “add fans.” But the effectiveness of cooling pads and fans is largely determined by two more fundamental factors: whether the roof and walls are insulated, and whether the pigs have enough cool water to drink. If the insulation is inadequate, the cooling provided by the pads is offset by radiant heat from the roof before it reaches the pens. If the water supply is insufficient, even good ventilation cannot help pigs withstand heat stress. Cooling is a system; equipment only makes sense when the steps are done in the right order.
Insulation comes first. The roof and west-facing walls of a pig barn are the main routes through which heat enters. Whitewashing the roof, installing shade structures, using light-colored building materials to reflect sunlight, and planting shade trees outside the barn all cost far less than cooling equipment, while directly reducing the heat that needs to be removed. Getting wall insulation and roof insulation in place during construction is more economical than installing fans inside the barn after production begins to “blow the heat away.” Once the insulation is done properly, the load that ventilation and cooling pads need to handle is smaller by an order of magnitude.
Ventilation is the second priority, followed by cooling pads. The design air speed for tunnel ventilation is usually 1.5—2.0 m/s, with the aim of moving airflow along the full length of the pig house to carry away heat and stale air. A cooling pad–fan system can typically lower the temperature in an enclosed pig house by 5—8℃, but there is one clear prerequisite: when outdoor humidity exceeds 75%—80%, the evaporative cooling effect of the pads will be greatly reduced. At that point, the main response should be to increase ventilation rather than continue running the cooling pads. In high-humidity regions, copying the cooling pad operating approach used in dry regions may fail to lower the temperature and can instead raise humidity inside the house, worsening heat stress. Farrowing rooms are especially sensitive to humidity, so cooling pads should be used more cautiously there to avoid additional problems for piglets and sows caused by a damp environment.
Water is the third priority, and also the factor most easily underestimated. In hot weather, a lactating sow may drink more than 32 liters per day, with the ideal amount close to 40 liters. The flow rate of drinking devices needs to be maintained at 1.8—2.0 liters/minute; the flow rate of drinking devices for finishing pigs should also be 1.2—2.0 liters/minute. If the main water pipe is buried too shallowly or exposed outdoors, the water inside can become so warm in summer that pigs are unwilling to drink it; even an adequate flow rate will not help. Burying the main pipeline at least one meter underground and adding insulation are measures that should be taken during construction. Spraying can serve as a supplementary measure for finishing pigs, for 5—10 minutes each time, but the amount of water should be controlled to avoid making the floor too wet and thereby raising humidity inside the house.
Get the order right: first reduce the amount of heat entering, then use airflow to carry heat away, and finally use water for evaporative cooling and physiological replenishment. Do it in reverse—install cooling pads first, add insulation later, and make do with the drinking-water system—and the equipment list may look complete, but heat stress in the pig pens will not improve significantly.
Insulation comes first. The roof and west-facing walls of a pig barn are the main routes through which heat enters. Whitewashing the roof, installing shade structures, using light-colored building materials to reflect sunlight, and planting shade trees outside the barn all cost far less than cooling equipment, while directly reducing the heat that needs to be removed. Getting wall insulation and roof insulation in place during construction is more economical than installing fans inside the barn after production begins to “blow the heat away.” Once the insulation is done properly, the load that ventilation and cooling pads need to handle is smaller by an order of magnitude.
Ventilation is the second priority, followed by cooling pads. The design air speed for tunnel ventilation is usually 1.5—2.0 m/s, with the aim of moving airflow along the full length of the pig house to carry away heat and stale air. A cooling pad–fan system can typically lower the temperature in an enclosed pig house by 5—8℃, but there is one clear prerequisite: when outdoor humidity exceeds 75%—80%, the evaporative cooling effect of the pads will be greatly reduced. At that point, the main response should be to increase ventilation rather than continue running the cooling pads. In high-humidity regions, copying the cooling pad operating approach used in dry regions may fail to lower the temperature and can instead raise humidity inside the house, worsening heat stress. Farrowing rooms are especially sensitive to humidity, so cooling pads should be used more cautiously there to avoid additional problems for piglets and sows caused by a damp environment.
Water is the third priority, and also the factor most easily underestimated. In hot weather, a lactating sow may drink more than 32 liters per day, with the ideal amount close to 40 liters. The flow rate of drinking devices needs to be maintained at 1.8—2.0 liters/minute; the flow rate of drinking devices for finishing pigs should also be 1.2—2.0 liters/minute. If the main water pipe is buried too shallowly or exposed outdoors, the water inside can become so warm in summer that pigs are unwilling to drink it; even an adequate flow rate will not help. Burying the main pipeline at least one meter underground and adding insulation are measures that should be taken during construction. Spraying can serve as a supplementary measure for finishing pigs, for 5—10 minutes each time, but the amount of water should be controlled to avoid making the floor too wet and thereby raising humidity inside the house.
Get the order right: first reduce the amount of heat entering, then use airflow to carry heat away, and finally use water for evaporative cooling and physiological replenishment. Do it in reverse—install cooling pads first, add insulation later, and make do with the drinking-water system—and the equipment list may look complete, but heat stress in the pig pens will not improve significantly.