Humidity is a physical quantity used to indicate the amount of water vapor in the air, commonly expressed as relative humidity. The relative humidity of the indoor air has a close relationship with the ambient temperature and has an impact on pigs. Whether it is young or adult pigs, when the ambient temperature is within the optimal range, the relative humidity of the air in the house has little effect on the production performance of the pigs.

Experiments have shown that if the temperature is suitable and the relative humidity changes from 45% to 95%, there is no abnormal weight gain in pigs. At this point, relative humidity is often limited for other reasons. For example, considering that dust is prone to float in the pigsty when the relative humidity is too low, and low relative humidity is also detrimental to the mucous membranes and disease resistance of pigs; Excessive relative humidity can facilitate the reproduction of pathogens and also reduce the lifespan of pigsty buildings and equipment. So even within the optimal temperature range, the relative humidity of the air inside the building should not be too low or too high.

When the temperature inside the house is low and the relative humidity is high, it will increase the coldness of the pigs. This is because the fur and skin of pigs absorb moisture from humid air, increasing their thermal conductivity and heat dissipation. At the same time, with ventilation and air exchange, a large amount of latent heat contained in water vapor is lost outside the building, reducing the building temperature. Therefore, when the house temperature is low and the relative humidity is high, it will affect the production performance of pigs, which is more sensitive to young pigs. For example, according to experiments conducted in pig pens with high relative humidity in winter, the average weight gain of piglets was about 48% lower than that of the control group, and they were prone to diseases such as diarrhea and enteritis.

Some people also believe that when the indoor temperature is high and the relative humidity is high, it can also affect the production performance of pigs. Pigs have a strong ability to adapt to changes in humidity, and even if the relative humidity exceeds 85%, it has little effect on growth performance. However, high humidity at high temperatures can hinder the evaporation and heat dissipation of pigs, thereby exacerbating the harm of high temperatures. If the temperature exceeds the appropriate range and the relative humidity increases from 40% to 70%, it will slow down the weight gain of pigs. Adult pigs are more sensitive to this because their suitable growth temperature is lower than that of piglets.

Taking all factors into consideration, the suitable relative humidity for pigs to live is 60% -80%. In certain regions or seasons, when the relative humidity inside the house is too high to be reduced, measures should be taken to increase or decrease the house temperature and carry out hygiene and epidemic prevention work, which can also ensure the normal production of pigs.

The investigation on the survival rate of poultry in the pig farm shows that the use of spray cooling equipment in the pig farm can quickly reduce the temperature in the use environment in hot summer, accelerate the air flow, neutralize the excessive positive ions in the air and increase the negative ion content in the air, thus improving the breeding environment, inhibiting bacterial breeding, reducing livestock diseases, improving the survival rate of livestock and promoting the healthy growth of poultry.