Animals experience optimal performance and health in their thermoneutral or comfort zone. If the temperature is above or below this range, the animal experiences heat or cold stress, respectively. The temperature the animal experiences (ie, the effective environmental temperature) is the temperature measured by a thermometer increased or decreased by other factors in the environment. These factors include heat loss by convection, conduction, and radiation. When the effective temperature falls below the animal's lower critical temperature (LCT), the animal's performance or health is sacrificed. The pig's LCT is based on its body weight and age