Figure 3. Pig Performance and Physiological Responses to Environmental Stresses.
At each stage of production, the physical environment (temperature, humidity, and air movements) can have a profound influence on pig performance responses. There is a range of temperatures at which the pig is comfortable (comfort zone), where weight gain and feed utilization are optimum. This comfort zone has a range of temperatures bracketed by a lower critical temperature (LCT) and an upper critical temperature (UCT). The environmental requirements within the comfort zone differ for each stage of the life cycle. The temperature range within the comfort zone can be influenced by several factors such as the type of housing and bedding conditions. Beyond the ranges of the comfort zone, the pig will modify its behavioral and physiological responses, which could lower its weight gain and feed-intake responses. The effects of environmental conditions, within the comfort zone and beyond the ranges of LCT and UCT, on different swine performance responses are presented in Figure 3.
Not only can the physical environment influence pig performance, but the pig's social environment (pen space, feeder holes per pig, group size, etc.) can also affect its performance response. For example, when pigs are housed in facilities with limited access to feeder space, or when the number of pigs per pen are over- or underpopulated, performance responses and cost of gain are affected.
Figure 3. Pig Performance and Physiological Responses to Environmental Stresses.