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Purdue University, West Lafayette, Indiana 47907
Abstract
Stress susceptible and stress resistant Hampshire barrows and gilts were subjected to a controlled heat stress of 35C, 65% relative humidity from 1100 to 1400 hr. and certain physiological responses were measured. During heat stress, body temperatures and respiration rates of both groups of pigs increased. Stress susceptible animals had greater elevations in body temperature. Blood pH of samples obtained via indwelling catheters from the anterior vena cava of susceptible pigs increased during the heat period, whereas blood pH of resistant animals did not change significantly. In both groups of animals, venous pCO2 and pO2 decreased during heat stress. Plasma adrenal corticoids increased significantly during the first replication of heat stress but did not follow this pattern when the stress was repeated, suggesting accumulative effects of stress on adrenal response or acclimation to the treatment. Stress susceptible and stress resistant pigs had similar plasma adrenal corticoid concentrations. Heat stress did not significantly affect serum creatine phosphokinase or glutamic-oxaloacetic transaminase activity or plasma protein concentration. As compared to the resistant pigs, susceptible animals had higher plasma protein concentrations which may contribute to increased blood buffering capacity.
1 Department of Animal Sciences. Journal Paper No. 5240 of the Purdue Agricultural Experiment Station.
2 Departments of Animal Husbandry and Food Science and Human Nutrition, Michigan State University, East Lansing 48823.
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