Investigation of a Locus on Chromosome 9 for Contributions to Pulmonary Hypertension Syndrome in Broilers

Although the ascites syndrome in chickens has been investigated for years, it continues to inflict financial losses to the world poultry industry. It is estimated that 8% of the 361 million broiler deaths are due to ascites leading to losses of millions of dollars annually. Efforts to curb the incidence of ascites are typically designed to slow early growth. This limits the birds\u27 ability to show its true genetic potential and impacts later yields. In 1994 lines divergent for susceptibility to ascites were established from a commercial sire line through sibling selection of birds reared at local altitude after testing siblings reared under simulated high altitude conditions. We used a whole genome SNP survey in our lines to identify regions associated with susceptibility. Seven potential regions were identified. Using microsatellite markers on chromosome 9 linked to genes with known contributions to Pulmonary Hypertension Syndrome, a survey of the lines (Generation -14) was accomplished. This survey revealed that the selected lines changed in allele frequency for the markers as compared to each other and the line of origin. Changes were consistent with patterns of susceptibility and resistance to ascites. In addition to the research populations, it was determined that three commercial lines are also segregating for resistance related alleles from these regions. The data support the predictive nature of these loci in that, the presence of a specific genotype is associated with resistance to ascites. These microsatellite markers show utility in several different lines and therefore, could be used for marker assisted selection to improve ascites resistance. Finally, economic impact of utilizing these markers was evaluated. Significant differences were found among the genotypes of a marker for absolute breast, percentage breast and percentage leg. Therefore, if these markers have to be super-imposed in commercial selection programs, there could be compromises on traits of economic importance