What effect does airflow have on the growth of pigs?

The effect of airflow on the pig's body mainly influences heat loss from the pig. Under general environmental conditions, as long as airflow exists, it can promote convective heat loss and evaporative heat loss from the body. When the ambient temperature is below the lower limit of the pig's suitable temperature, the effect of airflow increases the amount of heat lost from the pig's body, making the pig feel cold; at this time, in order to maintain body temperature, more energy must be consumed. Conversely, when the ambient temperature is above the upper limit of the pig's suitable temperature, because airflow helps the pig's body dissipate heat, and when the airflow is strong more heat is lost, increasing the wind speed can markedly improve the thermal environment for pigs and ease the adverse effects of heat stress on pigs.

In the effect of airflow on heat loss from the pig's body, besides airflow speed, the temperature of the airflow is also a very important factor; the cooling effect declines as the airflow temperature rises. When the airflow temperature equals the pig's skin temperature, the effect of convective heat loss disappears; when the airflow temperature is higher than the skin temperature, the body gains heat through convection; low-temperature and humid airflow can significantly increase heat loss, making the pig feel colder and possibly causing frostbite or death from cold. Airflow always acts together with temperature and humidity on the pig's body, easing or intensifying the degree of cold or heat stress.

According to reports, when the ambient temperature inside the house is 12°C, the airflow speed increases from 0.1 m/s to 0.26 m/s, and the heat loss of pigs weighing 25-30 kg increases by about 10%. For piglets weighing 2 kg, when the airflow speed increases from 0.1 m/s to 0.56 m/s, this is equivalent to a drop in ambient temperature of 4°C. Some experts believe that for piglets, the air speed should not exceed 0.3 m/s under any ambient temperature, otherwise it will cause the piglet's body to become cold and increase disease (such as pneumonia). Of course, when the ambient temperature is too high, appropriately increasing the airflow speed helps piglets cool down. However, the cooling airflow speed in all kinds of pig houses should not be too high; the friction of excessively high airflow will make pigs feel uncomfortable.

In winter, from the perspective of keeping warm, the speed can be lower than the values in the table. Under high-temperature conditions in summer, the speed can be higher than the values in the table to help the pig's body dissipate heat. However, according to reports, for pigs weighing 90 kg in a high-temperature environment of 48°C, if the floor is wet and the pig's skin is rolled wet on the floor, when the wind speed increases from 0.1 m/s to 0.9 m/s, after 30 minutes the rising body temperature can be reduced by about 2°C. But after the floor and the pig's skin are dry, even increasing the wind speed has no effect; it can be seen that in summer, for pigs, a livestock species without sweat glands, relying solely on increasing airflow speed to help pigs dissipate heat has a certain limit in its effect. Spraying and other measures must be added to give full play to the cooling effect of airflow.