MSU Extension

The summer season sometimes offers additional challenges in regard to managing finishing pigs. Heat stress can occur in all classes of pigs under a wide variety of situations and production systems. If pigs and facilities are not management properly, hot weather has a tendency to result in adverse effects in relation to finishing pig performance. Finishing pigs may begin to feel heat stress at approximately 70°F and an increase of respiration rate of finishing pigs may start at 72°F. In addition, temperatures above 85°F will have an impact on animal performance and the welfare of finishing pigs.

Pigs can modify their behavior to adapt to a wide range in temperatures. Although dry bulb temperature is a good place to start, this is seldom the temperature that the pig may be experiencing. There are many factors that may influence what the pig may be experiencing as far as temperature is concerned. These factors may include: air speed, humidity, group size, surface temperature, building materials, etc. The Effective Environmental Temperature (EET) of the pig involves all factors that affect the energy exchange between the pig and its environment.

Although we cannot control what mother nature deals to us as far as weather conditions are concerned, there are a few management strategies that can be implemented to help keep finishing pigs performing and to avoid the summer “stall out”.

Diet modifications

One strategy that may be implemented during periods of heat stress is to make modifications to the diet. Signs of decreased feed intake may be seen when temperatures reach approximately 77°F. In turn, nutrient levels need to be adjusted.

Dietary adjustments are one method to help maintain growth performance in summer months and will help in moderate heat stress situations. However, once the heat stress exceeds this level, the primary strategy switches to helping the pig lose heat and feel cooler. Furthermore, it is also important to evaluate the economics of diet modifications when attempting to manage heat stress.

Ventilation cooling

The purpose of hot weather ventilation is to replace hot air with cooler air, remove respired air from around the animal (which has very humid) and increase air velocity around the animal.

Sprinklers

Sprinkler cooling is an effective way to cool pigs in periods of heat stress. A sprinkler system that wets the animal and then allows the moisture to evaporate is preferred. Therefore, once the pigs are wet, stop sprinkling and allow the water to evaporate. If continual wetting takes place the relative humidity will rise and heat transfer through the evaporation method decreases which in turn defeats the purpose of the sprinkling system and may actually raise the temperature within the barn. For this reason, foggers should be avoided.

Air circulation - Stir fans

In order to get the best air distribution throughout the entire barn, circulation fans need to be set at a 15 degree angle toward the center of the barn. To determine the right number/spacing of fans, multiply the fan diameter (ft) times 25 and that will tell you how far the fans need to be apart. Consider the following example: if your fans are 2 ft. in diameter, then you need to have a fan every 50 feet (25 * 2 ft). Installed in this manner, the fans may ensure that evaporative cooling (drying) is maximized by increasing airflow when the pig is wet. However, it should be noted that installing fans for air circulation will not replace a good ventilation system.

Evaporative cooling pads

Evaporative cooling pads are also another option in the management of heat stress of finishing pigs. Evaporative cooling pads use the heat from air to vaporize water. In turn, air temperature is decreased but moisture is also increased. Cool cell pads can be effective in the hottest part of the day decreasing air temperature by up to 20° F.

Stocking density

The stocking density of a facility may contribute to the heat stresses of pigs for two reasons. First, if stocking densities are too high the temperature inside the barn may rise as more metabolic heat is added to the barn and the ventilation system may not have the capacity to function properly. Secondly, the pig will be unable to adopt its extended posture which would eliminate the possibility of increasing conductive heat loss. Keeping this in mind, pigs fail to lose maximum heat if any of its skin is in contact with other pigs. The general recommendation for space allocation of finishing pigs is 8 square feet. It is important to evaluate the ventilation system and make sure that the ventilation rate matches the size of pig and stocking density when dealing with pigs that are hot. In turn, the evaluation of the ventilation system and stocking density in the summer months may play a role in identifying any additional heat stresses that pigs in your barn may encounter.

The optimal goal when dealing with heat stress in finishing pigs is to minimize the amount of energy a pig spends to maintain its core temperature. Producers cannot rely simply on dry bulb temperatures and LED controller read-outs to assess whether pigs are in heat stress. There are many confounding factors such as humidity and air speed that complicate matters, meaning that what appears to be an acceptable air temperature may still be a heat stress situation for the pig. Daily observations of the behavior of your pigs may be the most telling in regard to the management of heat stress in finishing pigs.  

To view full article, please see the MSU Pork Quarterly.