Determination of corticosterone concentration in plasma of turkeys using raioimmunoassay

A method of determining corticosterone concentration in turkey plasma was developed using radioimmunoassay. Compared to fluorometric analysis and competitive protein-binding radioassay, this method had the following advantages: 1) results were consistent, 2) the method was simple and rapid to perform, 3) only 20 lambda of plasma was required, 4) all procedures were performed using the same tube except for counting, and 5) unknown and standard samples were treated identically. The coefficient of variation with the 5 ng/ml standard sample between 14 sets of assays was 12.6% and the average coefficient of variation within duplicate assays of unknown samples randomly selected from each of the 14 series was 4%. Using this method, there was an increase in the average plasma corticosterone concentration in all groups of inoculated turkeys one day after inoculation of Pasteurella multocida which was significantly (P less than .05) greater than that of the noninoculated groups.