Periods of elevated temperatures also can harm the gilt pool. It is not uncommon to see increased periods of anestrus, shorter estrus periods, and lower conception rates in gilts during this time. In controlled studies, when higher temperatures were found to induce anestrus in gilts, cyclicity resumed after exposure for as little as 1 to 2 days to a relatively normal thermal environment. It may be possible to utilize this concept on commercial farms by constructing a "cool zone" in the breeding barn for the gilts. The minimum period that gilts will need to be exposed to this environment to resume cycling has not been determined, which means that if 2 to 3 weeks of gilts are required, a fairly large area in the breeding barn may be needed. Furthermore, cold water and air movement may not be sufficient cooling mechanisms when one considers humidity to be an equal contributor to heat stress. Consequently, some type of air conditioning system may be needed to remove humidity. The cost of this type of system may not be justified unless there are extensive problems with anestrus (< 10% cycling).