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Temperature Extremes and Youth Market Hog Project Pigs

Livestock Update, August 2005

Allen Harper Extension Animal Scientist Swine, Tidewater AREC

An important consideration with housing management of 4-H and FFA project pigs is that hogs and pigs are sensitive to environmental temperature and air quality (ventilation). Growing-finishing market hogs (45 lb to market weight) can tolerate a fairly wide range of temperatures. However, excessively cold or excessively hot temperatures will cause stress, poor growth and more health problems. As the market hog grows, it becomes less sensitive to colder temperatures but more sensitive to hotter temperatures. Figure 1 shows the lower critical temperature (lower black line) and upper critical temperature (upper black line) of market hogs at different stages of growth. The area between these lines is considered to be the pig's comfort zone, also referred to as the thermo-neutral zone.

As hogs are exposed to temperatures progressively colder than the lower critical temperature, they must use more feed energy to maintain body temperature. Hogs stressed by cold temperatures grow slower and convert feed to body weight less efficiently. Exposure to very cold temperatures for extended periods of time may weaken the hog's immune system, making it more likely to develop respiratory or intestinal health problems. Preventing cold stress during the market hog project may involve supplying supplemental gas heat if the hogs are housed in a totally enclosed facility. However, this can be costly and is not practical in cases where lower-cost open-front housing is used for the project animals. In this situation providing wind protection for the hogs on three sides, a roof overhead and clean, dry bedding in the sleeping area are adequate to prevent to cold stress. Dry bedding on top of a solid concrete or wooden floor in the sleeping and loafing area does an excellent job keeping growing hogs warm in cold seasons. Good cold weather bedding materials include straw, wood shavings, peanut hulls or similar materials. Removing damp, soiled bedding and replacing it with fresh dry material is an important practice during cold weather. Damp bedding has poor insulation value and does not protect hogs from cold temperatures. Housing several pigs together during cold weather has an advantage over single pig housing because the animals can huddle together to conserve body heat.

During this time of year we are dealing with the other temperature extreme. When hogs are exposed to temperatures progressively higher than the upper critical temperature, they become lethargic and eat less feed. As a result, the hog's growth is much slower during very hot weather. In cases of extended periods of high heat stress, hogs may stop eating and growing entirely. Because hogs have a very limited ability to sweat, providing water for wet skin cooling can be very effective. Mister nozzles, sprinklers and drip nozzles are used on commercial farms to allow the hog to wet its skin. Similar devices can be set up for small-scale market hog projects. Only a very small amount of water needs to be applied to the pig or the pen floor. It is not water directly, but the evaporation of the water that cools the hog. Good ventilation improves the evaporation process and removes gases and odors such as ammonia that can build-up in the facility. Summer shade is critical too because hogs sunburn quite easily. If possible, avoid the use of mud holes in earthen lots to cool hogs. Mud holes can be unsanitary and make project pigs difficult to clean for youth shows. However, unlimited fresh drinking water should be available to the pigs at all times during all weather conditions.

Figure 1. Market Hog Temperature Zones

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