DIFFERENTIAL GENE EXPRESSION IN LUNG TISSUE OF WOODEN BREAST SYNDROME AFFECTED AND UNAFFECTED COMMERCIAL BROILER CHICKENS

Behnam AbashtFor years, the commercial boiler chicken industry has focused its breeding efforts on producing feed-efficient broiler chickens that produce large amounts of meat in a short amount of time to accommodate the high consumer demand for poultry products. The economic welfare of the poultry industry is dependent upon the quality of the meat produced; therefore, the rise in muscle disorders and myopathies that jeopardize meat quality are concerning to growers. This study focuses on the novel muscle disease, Wooden Breast Syndrome, which is characterized by an abnormally hard pectoralis major muscle. Many studies have also identified muscle hypoxia and oxidative stress as significant symptoms of Wooden Breast Syndrome indicative of respiratory system impairments. In particular, this study will characterize gene expression differences in the lung tissues of affected and unaffected commercial broiler chickens using functional analysis tools to determine which specific pathways or cellular functions are affected by this disease. The purpose of this research is to gain a better understanding of the disease etiology of Wooden Breast Syndrome, to understand how it affects the health of commercial broiler chickens, to gain insight into ways to remedy hypoxia and oxidative stress in affected birds, and to understand the lung’s contribution to this disease. Starting in March 2017, a large live animal experiment on Wooden Breast Syndrome was conducted in which approximately 2,100 broilers were raised to market age. After being euthanized by cervical dislocation, birds were examined for Wooden Breast Syndrome, necropsies were performed, and tissue samples were taken from the breast muscle, liver, and lung. For this study, a total of 12 samples were used, including 6 affected (3 females and 3 males) and 6 unaffected (3 females and 3 males). Differentially expressed genes in the lung tissues between unaffected and affected birds were identified by RNA analysis and functional analysis was completed using IPA® Functional Analysis Software. A total of 141 differentially expressed genes were identified using Cuffdiff v2.2.1. The top upregulated (heat shock proteins, SPP1, FABP4, etc.) and downregulated (ALB, HSD17B2, SELENOP1, etc.) differentially expressed genes were selected based on the most positive and negative Log2 fold change, respectively. Functional analysis of the differentially expressed genes using IPA® identified 5 top canonical pathways, several upstream regulators, and diseases or functions that were significantly activated or inhibited in the affected birds. The results suggest Wooden Breast Syndrome affects lipid metabolism and hypoxia and oxidative stress in the lung tissue. Analysis of the DE genes identified in lung tissue from broilers affected with Wooden Breast Syndrome suggest the lungs do not have a significant role in the development of Wooden Breast Syndrome. There is not enough evidence to support that markers of immune response, hypoxia, and oxidative stress found in affected lung tissues are activated by issues originating from the lung, as these responses can also be attributed to the systemic impact of Wooden Breast Syndrome. A well-supported finding from this research is the altered lipid metabolism in affected lung tissue, which has been consistently observed in various tissues in broilers affected with Wooden Breast Syndrome. These are only preliminary findings; therefore, the lungs’ involvement in Wooden Breast Syndrome cannot be entirely dismissed, as additional studies must be completed to explore significant genes and pathways identified by this research.Biological Science