How to Avoid Production Losses in Swine Due to Heat Stress
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Long, hot, humid summer days can result in heat stress in pig operations. A study released by Ohio State University in 2003 concluded that heat stress costs the U.S. pork industry approximately $300 million each year.
Although pigs are generally raised in facilities with a controlled environment, it is not always possible to avoid high temperatures within the barns. Temperatures above 23°C can have negative impacts on animal performance. In extreme cases, heat stress in pigs can lead to death loss. For both animal welfare and business reasons, it makes sense to take measures to reduce the impact of hot weather on pigs.
Heat stress occurs when the environmental temperature rises to a point where the animal is producing more heat from metabolism, or receiving more heat from its surroundings, than it is transferring from its body to its environment.
Heat stress is a concern with pigs because they do not have functional sweat glands to help them reduce body heat. They lose heat to their surrounding environment by conduction, thermal radiation, convection and evaporation to maintain their ideal core body temperature. If temperature and relative humidity are too high, pigs can no longer maintain their ideal body temperature.
Figure 1 shows a Heat Stress Index for grow-finish pigs, determined by temperature and relative humidity, that can be used to assess the risk to animals under various conditions.
Figure 1. Heat stress index for grow-finish pigs. Adapted from H. Xin and J. Harmon. 1998.
Under heat stress conditions, the goal is to minimize heat transfer to the animal from the surroundings and maximize heat transfer from the animal to its environment. Recognizing the potential for heat stress, or that pigs are experiencing heat stress, is the first step in helping the animals cope with a hot, humid environment.
Pigs will try to increase heat dissipation and decrease body heat production. To support this:
Table 1. OMAFRA ventilation rate guidelines
a Summer ventilation rate for large pigs may have to
be increased to 1 air change/min. during hot summer weather.
Source: Ventilation for Livestock and Poultry Facilities, Pub 833, OMAFRA.
It is important to recognize when temperature and humidity can increase the risk of heat stress in pigs. By recognizing when pigs are experiencing heat stress, and knowing how to help them cope, we can prevent or reduce production losses during periods of hot weather.
The weather cannot be controlled. Plan ahead and have strategies in place to deal with hot weather when it happens.
Death loss due to heat stress is most often attributed to power outages in hog barns when there is no alternate power source or power loss back-up plan. Test your alternate power generation and power outage alarms monthly for fan-operated barns. Check panic doors/drop curtain releases for naturally ventilated barns. Heat build-up in non-ventilated barns can cause fatalities in all seasons.
Transport during any season can cause heat stress in pigs and may result in death loss. Producers can mitigate this in the following ways:
Enter temperature and relative humidity on your Blackberry or Android smartphone to estimate heat stress risks quickly and easily with the Heat Stress in Livestock and Poultry App. The app also suggests steps to take to reduce heat stress to maintain feed intake and productivity.
Download the free Heat Stress in Livestock and Poultry App from Blackberry World or Google Play. The app features English, French and Spanish options.
This factsheet was written by Jaydee Smith, Swine Specialist, OMAFRA, Ridgetown, and Laura Eastwood, Swine Specialist, OMAFRA, Stratford.
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