Water intake is not solely under the infl uence of physiological requirements,
because behavioral mechanisms are also involved (Fraser et al.,
1990). It is well known that when bored, or heat stressed, pigs will play
with drinkers; this will increase water disappearance, and at least in the instance
of heat stress, intake. Pigs consume luxury amounts of water, well
beyond what would be considered physiological need. Hunger-induced
polydipsia occurs in limit-fed pigs, such as gestating sows, but can be seen
in growing pigs as well (Yang et al., 1981). Schedule-induced polydipsia
is also observed in swine and results in excessive water intake.