Acute heat stress effects on total heat production, respiration rate, and core body temperature in growing-finishing swine

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 core body temperature (CBT) and to investigate the dynamic interaction of these parameters in growing-finishing barrows. Sixteen high-lean-growth barrows were randomly assigned to a set of treatments as dictated by a 4 × 4 Latin square crossover design. Pigs were moved from an individual pen to an indirect calorimeter where one of four environmental treatments (TRT) (18, 24, 28, 32 C) were applied for 20 h. During the treatment exposure RR, THP, RQ and CBT were measured. For the two-week period between treatments, pigs were housed at thermoneutral (22 C). Total heat production 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.