Date of Graduation


Document Type


Degree Name

Doctor of Philosophy in Poultry Science (PhD)

Degree Level



Poultry Science


Walter G. Bottje

Committee Member

Sami Dridi

Second Committee Member

Billy Hargis

Third Committee Member

Tyrone Washington

Fourth Committee Member

Byung-Whi Kong


hormone receptor, mitochondria, orexin, poultry


Mitochondria are vital to the proper growth and function of muscle cells since they’re responsible for the majority of ATP production used for cellular energy. Previous studies have investigated how differences in mitochondrial function affects feed efficiency (FE) in broilers phenotyped for High and Low FE. Low FE broilers have been shown to have increased levels of reactive oxygen species (ROS), thus contributing to higher levels of oxidative stress and damage seen in these birds. Global gene and protein expression studies conducted on breast muscle of the High FE and Low FE phenotypes have suggested that differences in mitochondrial function and hormone signaling play a role in feed efficiency. In mammalian muscle cells, hormones such as the neuropeptide orexin are known to affect mitochondrial function. Therefore, the focus in this study was to determine whether hormones can affect mitochondrial dynamics in avian muscle cells, compare the expression of genes involved in muscle growth and insulin signaling in the High FE and Low FE phenotypes, and determine whether hormone receptors are present in the mitochondria of avian muscle cells. The actions of hormones and their receptors play an important role in the regulation of growth and metabolism. Investigation of orexin expression in avian muscle cells revealed that the hormone and its receptor are expressed in muscle. Orexin was also shown to be secreted by muscle cells and caused differential expression of a number of mitochondrial-related genes. Based on predictions generated by the results obtained from global expression studies, qRT-PCR analysis revealed several differentially expressed genes between the High and Low FE phenotype that are associated with muscle growth/development and the insulin signaling pathway. Lastly, due to the lack of scientific literature concerning the expression of hormone receptors in the mitochondria of avian muscle cells, studies were conducted that do indicate the presence of receptors in muscle mitochondria.