U.S. Department of Agriculture: Agricultural Research Service, Lincoln, Nebraska



Stephen D. Kachman

Document Type


Date of this Version



Published in Livestock Production Science 71 (2001) 253–260.


Researchers and producers alike have noted the increased susceptibility to heat stress exhibited by the newer genetic lines of pigs. A study was conducted to gather baseline information on the effects of acute heat stress on total heat production (THP), respiratory quotient (RQ), respiration rate (RR), and rectal temperature (Trectal ) and to investigate the dynamic interaction of these parameters in growing–finishing barrows. Sixteen moderate–lean growth barrows were randomly assigned to a set of treatments as dictated by a repeated 4x4 Latin square crossover design. Pigs were moved from an individual pen to an indirect calorimeter where one of four environmental treatments (18, 24, 28, 32°C) were applied for 20 h. During the treatment exposure RR, THP, RQ and Trectal were measured. For the 2-week period between treatments, pigs were housed at thermoneutral (22°C). THP was found to be 17–20% higher than the published standards but comparable with other contemporary studies. Respiration rate was found to be a leading indicator of stress.