Minimizing Heat Stress in Pigs

Posted: August 24, 2017 | Written By: Lacey Hanson, Form-A-Feed Swine Intern

form-a-feed pig

Managing heat stress is crucial in maximizing swine productivity and production. According to Iowa State University, heat stress causes an estimated $330 million in annual losses to the United States swine industry.  During heat stress, the pigs’ body experiences an increase in the blood plasma pH and a decrease in intracellular pH. The pig will have a more difficult time fighting off diseases and pathogens. Additionally, the hormones responsible for stress will become prevalent within the blood.

The first symptoms of heat stress you are likely to notice is a decrease in feed consumption and a significant increase in water consumption. A pig experiencing heat stress may consume as much as 6 times the amount of water than normal. A producer will also notice an increase in the pig’s respiratory rate, and pigs will be lying sporadically throughout the pen. After a period of time, heat stress can cause pigs to lose electrolytes resulting in weak and lethargic pigs. Other symptoms of heat stress include muscle trembling, a reduced pulse rate, and an increase in mortality rates.  A publication by Pearce et al. (2013) explains the damages done to the intestinal formation of pigs when exposed to heat stress. According to this research, pigs exposed to 95°F temperatures for 24 hours experience considerable damage to their immune system and increases plasma endotoxin levels. The research went on to demonstrate even a short exposure (1-2 hours) to heat stress places pigs at a much higher risk of infection.

There are several practices that can be utilized in order to reduce heat stress. One way is to ensure the barn ventilation is at the proper rate. Having a steady airflow will help the barn stay cool. The recommended ventilation rates according to Iowa State University are represented by the following table.

 Recommended Ventilation Rates (MWPS)

Minimum Hot Weather
Sow & Litter 20 cfm/sow 500 cfm/sow
Nursery 12-30# 2 cfm/pig 25 cfm/pig
Nursery 30-75# 3 cfm/pig 35 cfm/pig
Finishing 75-150# 7 cfm/pig 75 cfm/pig
Finishing 150-250# 10 cfm/pig 120 cfm/pig
Gestating 12 cfm/sow 150 cfm/sow
Breeding 14 cfm/sow 300 cfm/sow

CFM: Cubic Feet per Minute

As an example, if you have a 1200 head finisher with pigs weighing 100 pounds your recommended ventilation rate during hot weather would be 90,000 cfm (1200 head x 75 cfm/pig=90,000 cfm). Knowing how to use your ventilation control and ensuring that your ventilation is at the correct rate will greatly improve pig performance within the barn.

Sprinklers can be a very useful tool in avoiding heat stress when used in conjunction with ventilation. Air circulation allows for the water on the skin of the pig to evaporate, cooling the pig. Dr. Luiz Souza from the University of Minnesota Extension suggests, sprinkling water for 1-2 minutes and allowing 20-30 minutes for evaporation to occur and then repeating the process.  The goal with sprinkling is to wet the pigs, then allow for evaporative cooling. Saturating the air and pigs with water can actually be a negative if this cooling period is not allowed.

Other techniques to reduce heat stress include: reducing stocking rates, using an electrolyte supplement such as Capture or Swine BlueLite®, increasing diet nutrient density (energy and amino acids), and providing a secondary or additional water sources. Having a complete understanding of your barn’s ventilation systems, as well as implementing the other practices listed above during hot weather, will greatly reduce the negative impacts of heat stress and will allow for more optimal productivity.