Hubert, Shawna Marie (2019-08). Functional and Genomic Drivers of Wooden Breast in Commercial Broilers. Doctoral Dissertation.
Commercial meat-chickens (broilers) have been heavily selected for performance traits including high body weights, large breast muscle size, and improved feed efficiency. The wooden breast condition (WB) is a consequence of this selection along with several other physical and metabolic disorders. WB is currently considered a myopathy unique to broilers, causing decreased meat quality. It is not considered a threat to bird or consumer health, but inflammatory tissue due to WB is required to be excised during processing. The objective of this investigation was to detect molecular characteristics of WB through the use of global transcriptome and mitochondrial genome based comparative analyses between slow-growth chickens and commercial fast-growth broiler breeds. Our first investigation revealed that WB is genetic in origin and likely involves multiple organ systems. These findings are based on identification of an age-dependent transcriptional profile demonstrating altered regulation of cell proliferation and glycolysis, and markers of oxidative stress. Through our second investigation we observed the impact of dietary omega-6:3 ratio on age and breed related gene expression patterns and pinpointed genes specific to broilers and the characteristics of WB. Among the top pathways influenced were glycolysis, oxidative phosphorylation, and mitochondrial dysfunction, signifying the regulation of energy metabolism as central to the pathophysiology of WB. The third study illustrated a nuclear interaction with mitochondrial oxidative phosphorylation gene expression and deficiency in 42-day old broilers. This deficiency indicates an inability to produce adequate energy to support the high metabolic rate of broilers and provides illumination to the role of the mitochondria in WB. Overall, these findings indicate that genes important to energy metabolism, cell proliferation and survival, and inflammation have been altered by selective pressure for broiler performance traits and their dysregulation has multi-system consequences which manifest macroscopically as WB. Functional classification of these genes showed commonalities between the genes in these lists suggesting that broilers share the biomedical profiles of obesity, diabetes, and cardiovascular disease.