Radiant losses to cold surfaces such as poorly insulated walls, and ceilings, even though the animal is not touching the surface. This is the feeling you get when you sit beside a single pane glass door in winter time as compared to sitting beside a heavily insulated wall. Your body heat is being used to warm that glass door.
Convective losses to surfaces the animal actually touches, especially floors. Concrete and metal floors are much “colder” than plastic, rubber mats or wood. Pigs lose half as much heat to a wooden floor as to concrete and only one-sixth as much to a plastic floor. However, wood is impossible to clean and disinfect so it is not recommended as a permanent flooring material. Slatted floors are much colder than solid ones, regardless of material.
Evaporative loss of heat from the surface of the pig’s body occurs whenever the pig gets wet. Evaporation of water from the skin takes heat with it. This is the cold, shivering phenomenon you feel when you get out of a warm shower and step into a cold room. Examples include accidentally spraying pigs while washing down facilities, pigs lying in their own feces and urine, wet floors from leaking water cups or using water to clean pens. We use this principle to keep finishing pigs cool in the summer by spraying or misting them during the heat of the day.
How much do these losses of heat influence the way the environment feels to the pig; i.e., the Effective Temperature? For example, a slight draft of 40 ft/minute feels chilly to a 3-4 week old pig and makes an 80º room feel like 73º. This minimal draft is often not even detectable by people. A draft of 100 ft./minute will make that same room feel like 67º. Poor insulation in walls and ceilings and wet, cold floors will drop the Effective Temperature by 7º with each factor.
Therefore in a room where the thermometer at pig level reads 80º but there is a slight draft (-7º) and the concrete floors are wet (-7º), the pigs will feel like its 66º. Lack of insulation will drop Effective Temperature another 7º to 59ºF.
Now for the good news. Providing a deep dry, straw bed will increase effective temperature by 8-12º. Therefore, pigs in a pen at 70º will feel more like 80º. As a general guide, dry straw bedding will make up for most of the harmful effects of cold, wet floors and lack of insulation. However, drafts can still be a major problem, especially for 30-50 lb show pigs purchased by youth in winter or spring when night temperatures are in the 30’s or 40’s, even if a deep straw bed is provided. At best, even with no drafts, the effective