Cilkiz, Kubra (2018-08). Genome-Wide Association Study of the Woody Breast Myopathy in Broiler Chickens. Master's Thesis.
Increasing demand for poultry meat has encouraged production of the maximum possible yield from chicken, which resulted in broiler chickens being subjected to intense selection for increased Pectoralis major (P. major) breast muscle yield and growth rate. That is presumed to contribute to development of new myopathies, which mainly impairs the nutritional value of the meat and meat quality, and in turn, affects consumer acceptance. A recent and prominent example is woody breast (WB) myopathy characterized by palpably tough breast muscle, which imposes an additional economic burden on the poultry industry. The basis of WB myopathy is not known yet but is suspected to be genetic due to its association with growth rate. Development of the WB myopathy is tightly linked to growth rate, which is under intense selection. On the other hand, growth rate and body mass are complex traits, and WB myopathy is associated with growth rate, which suggests that WB myopathy is more likely a complex trait. Genome-wide association studies (GWAS), which have become more feasible with recent improvements in high-throughput genotyping technologies, were exploited with the aim of the investigating the underlying etiology and genetic mechanism of woody breast myopathy. Using 600 K HD Affymetrix Axiom Array, 10 affected broilers and 10 healthy White Plymouth Rocks (WPR) were genotyped. SNPs and constructed haplotype blocks were examined whether they exhibited statistically significant association with woody breast myopathy. The current study conducted by SNPs and haplotypes suggested that several biological pathways and genes associated with oxidative stress, Ca2+ binding, microtubule motor activity and cellular repair could be contributing factors regarding the onset of woody breast myopathy. However, analysis of results clearly showed that the sample introduced biases related to selection of study participants into the association analysis. Due to small sample size, after correcting for population stratification, it was not possible to detect true disease variants or genes genuinely affecting woody breast myopathy.