Plasma Corticosterone Concentrations in Turkeys Inoculated with Pasteurella multocida and Maintained at High and Low Environmental Temperatures

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Abstract
Radioimmunoassay was used to determine plasma corticosterone concentration (PCC) in turkeys inoculated with P. multocida via the palatine air spaces or the drinking water and maintained at high (33.4-37.4.degree. C), low (2.6-5.3.degree. C) and moderate (19.8-22.4.degree. C) temperatures in temperature-controlled chambers. In uninoculated turkeys maintained at high temperatures, the PCC was generally lower than in turkeys maintained at moderate temperatures; the opposite occurred in turkeys maintained at low temperatures. After inoculation with P. multocida, all groups of inoculated turkeys showed an increase in the average PCC which attained a level in some turkeys of over 40 ng/ml compared to 1.8-27.2 ng/ml in the uninoculated turkeys. This increase was proportional to the severity of the infection that developed. The PCC was a sensitive indicator of an incubating infection of P. multocida since it was markedly increased in turkeys that were bled 1 day before the onset of depression. In turkeys inoculated via the palatine air spaces and maintained at 20.degree. C, the PCC on the day of inoculation was significantly (P < 0.05) lower in the turkeys that later died than in those that survived. The PCC was generally higher in the turkeys that either died between 5-10 days after inoculation or were depressed at the end of the experiment on day 10.