Serological Patterns in Layers in the U.K.

Layer chickens are vaccinated more intensively than broilers but less intensively than broiler parents. The purposes of vaccination are:

1. To protect the layers against mortality and morbidity during rear.

2. To protect against drops in egg production and reduced internal and shell quality during lay.

3. To reduce or eliminate the transmission of pathogens to successive crops on the same farm or to other farms.

Serological monitoring of the response to vaccination and/or field challenge is relatively rarely practiced in layers, hence the reduced number of assays reported here (3354) . Most data presented here represents investigation of particular disease problems during the period January 1993 to September 1994. As for meat type chickens, no data have been excluded except for records for which the age of the birds was not informed or recorded.

A summary of the assays carried out in layers is shown in Table 7. No samples positive were detected in the serum agglutination test for M.g. However 10% of the 487 samples tested for M.s. were positive, suggesting that M.synoviae is still present on some layer sites. Only 4% of the 761 samples tested for S.enteritidis antibodies were found to be positive. Only a small proportion of samples were tested for EDS-76 by HI (6 groups, 69 samples). About half (47.8%) were positive, though this is to be expected since many would have been vaccinated.

The remaining results are summarized in charts on the following pages.

Detailed information on Specific Diseases: