Section 3. Practical Applications of Poultry Serology

The implementation of the custom-designed computer programme described in an earlier section has given access to a large volume of serological data. The data are saved in various formats with differing degrees of detail. The form which is used most frequently in retrospective analyses stores a summary of the data generated by one assay for one group of birds (usually a house-flock) in a single data-base record. Each record includes data descriptive of the group (reference number, company, farm, house, age, date received). In addition the data describe the number of sera tested and the number falling in each result category, a mean result for the group and a standard deviation. The record also has information of general administrative and QA use (when assay was done, by whom, and antigen batch number in some cases). The data files are imported into a commercial data-base programme (Paradox) then the records of interest are selected by specifying an assay, species, company, age and so on. The graphs shown in the following sections were prepared by exporting the selected records to a programme with a spreadsheet module (Microsoft Works). Within the spreadsheet charts were prepared usually by plotting mean response against age. The spreadsheet was also use to calculate regression analyses.

Charts have been prepared from a data-base representing 68776 individual sample assays on broiler parent chickens, 53532 assays from broilers and 3354 from layers. Most of the following charts show a scatter of mean serological response for the assay for all groups (house-flocks) in our data-base. Where a regression line is added to the charts this can be taken to represent the mean response of the population. These charts are a convenient way of comparing the response of a particular group of birds with that of a population of similar groups of birds. In interpreting the results of a specific group of birds it is also necessary to take into account the range pattern and uniformity of response and the interval between disease occurrence or vaccination and the date of sampling.