Environmental conditions can play a major role in the performance of growing-finishing pigs. The optimum temperature range is 64 degrees to 70 degrees F. Extreme hot or cold temperatures, high humidity, and wind can have a negative effect on pig performance.
Cold Stress
Cold stress on growing-finishing pigs in the South is caused by management as much as it is by temperature. Cold temperatures increase the pig's energy requirements. Additional feed is required to maintain body temperature (Tables 1 and 2). Therefore, cold stress usually results in an increase in feed intake. In extreme conditions, feed intake can increase as much as 25 percent. Winds and high humidity will increase the effect of cold temperatures.
In the South, ample shelter and stocking rates reduce the effects of cold environmental temperatures. Bedding will also reduce cold stress in sheds (shelters), and in open-fronted and open-sided facilities with solid floors. In curtain-sided or environmentally controlled barns, cold stress should not exist. Growing-finishing pigs will generate enough heat to warm the barn under most conditions.
Addition of fibrous ingredients in the diet can also reduce the effects of cold temperatures. Oats and barley contain 7 to 12 percent fiber. Dietary fiber will increase the amount of heat produced by the pig and dilute the energy content of the feed. The result is more efficient use of the energy in the feed.
Heat Stress
Heat stress is a greater problem with growing-finishing than is cold stress. As the temperature rises above 70 degrees F, feed intake will begin to decline (Table 2). Pig weight gains will decrease with feed intake. For heavier pigs, feed intake can be as low as 25 to 30 percent below normal at 90 degrees F.
Housing can minimize if not eliminate heat stress. In drylot facilities, shade can reduce the temperature by as much as 10 degrees F. In open-fronted or curtain-sided facilities, wind reduces the effects of heat stress. Circulating fans create air movement that will work like natural air movement. Sprinkler systems provide additional cooling for all types of facilities, from drylot to environmentally controlled. Sprinklers for a typical finishing pen should provide 0.60 gallons water per minute per animal. Use intermittent rather than constant sprinkling. Systems should be designed to run 1 to 2 minutes each half hour or 1 minute out of 10. One nozzle, 6 feet above the floor, is adequate for this size pen. When a pig gets wet, evaporation will help lose body heat and reduce the stress level. Overcrowding adds to the heat load and increases heat stress, but following accepted space requirements will eliminate this factor. In environmentally controlled facilities, adequate ventilation is critical. Fan systems should be designed to meet summer ventilation requirements. They should be routinely cleaned and maintained. Fan controls should also be checked periodically.