2006 Annual Report 4d.Progress report. This report serves to document research conducted under an agreement between ARS and Wageningen Agricultural University, The Netherlands. Details of the research can be found in the report for the parent CRIS 3635-31320-007-00D Genomics and Immunogenetics of Economically Important Traits of Poultry, and reimbursable agreement 3635-31320-007-15R. Efforts are currently underway to determine the extent of linkage disequilibrium in commercial poultry populations. In other words, we wish to find out the average size of the genomic regions shared to each bird. This information is useful in calculating how many genetic markers are needed to screen the entire chicken genome. The expected results will greatly aid scientists and poultry breeders in identifying genes of agricultural importance, e.g., disease resistance, egg and meat production.