Plasma corticosterone concentrations in turkeys inoculated with Pasteurella multocida and maintained at high and low environmental temperatures.
Radioimmunoassay was used to determine plasma corticosterone concentration (PCC) in turkeys inoculated with Pasteurella multocida via either the palatine air spaces or the drinking water and maintained at high (33.4-37.4 C), low (2.6-5.3 C) and moderate )19.8-22.4 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, whereas 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, in relation to the average in the uninoculated turkeys, which ranged from 1.8 to 27.3 ng/ml. This increase was proportional to the severity of the infection that developed. The PCC was found to be a sensitive indicator of an incubating infection of P. multocida, since it was markedly increased in turkeys that were bled one day before the onset of depression. In turkeys that were inoculated via the palatine air spaces and maintained at 20 C, the PCC on the day of inoculation was significantly (P less than 0.05) lower in the turkeys that later died than in those that survived. Generally, the PCC was higher in the turkeys that either died between 5 and 10 days after inoculation or were depressed aa the end of the experiment on day 10, relative to the turkeys that were alert at the end of the experiment.