ARS | Publication request: Heat Stress Effects on Growing-Finishing Swine

Submitted to: Annual Carolina Swine Nutrition Conference
Publication Type: Proceedings
Publication Acceptance Date: October 22, 2009
Publication Date: November 10, 2009
Citation: Nienaber, J.A., and Brown Brandl, T.M. 2009. Heat Stress Effects on Growing-Finishing Swine. In: Proceedings 25th Annual Carolina Swine Nutrition Conference, 10 Nov. 2009, Raleigh, NC. pgs. 25-35.

Interpretive Summary: This paper presents a summary of the effects of high environmental temperatures on swine. High temperatures and humidity cause pigs to reduce the amount of feed they eat and they grow more slowly. The changes in their eating can also cause changes in the fat and lean contents of their carcasses. Extreme heat can also lead to sickness and death. There are several visible signs that pigs are being stressed by the heat. The reduced feed intake is one, but another is a change in behavior. When hot, pigs become lethargic and seek wet areas. They will lie under a nipple drinker or "mess" in their pens to get wet. Fighting for a spot near water and increases in noise are also signs of heat stress. Air movement is important to help animals cope with heat stress. Some type of water sprinkling is helpful, but it should be intermittent to let the animals dry off. It is the evaporation of water that gives the cooling effect. While air conditioning is generally too expensive, evaporative cooling methods work and can be economical. Producers should avoid unnecessary movement of animals and should schedule handling of pigs during the coolest part of the day or night.

Technical Abstract: Understanding the factors that create heat stress, the response of the animals while under heat stress, and the signs of heat-stressed swine are essential to making rational decisions for the selection, design, and management of their environments. Heat stressors include combinations of environmental temperature, humidity, wind speed, and radiation. Swine are generally clean animals, however, under heat stress, they will seek areas of wetness to increase evaporative heat loss from wet skin. Pen "fouling" is a ready sign of heat stress. Swine vocalizations increase as swine become more lethargic and are reluctant to move from a wet spot. Swine reduce feed intake in an effort to reduce metabolic heat load. This will also cause a reduction in growth and may negatively impact feed utilization, body composition, and even animal health. Because of the complex interaction of available nutrients, genetic growth potential, and environmental temperatures, it is important to understand the correlations among these factors when planning or managing a swine production system.