Submitted to: Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 11/16/2010
Publication Date: 8/1/2011
Citation: Fadly, A.M., Cheng, H.H., Dunn, J.R., Heidari, M., Hunt, H.D., Lee, L.F., Silva, R.F., Zhang, H. 2011. Avian Disease and Oncology Laboratory (ADOL) research update. Proceedings One Hundred and Fourteenth Annual Meeting of the United States Animal Health Association (USAHA), November 11-17, 2010, Minneapolis, Minnesota. p. 528-530.
Technical Abstract: GENOMICS To meet the growing demands of consumers, the poultry industry will need to continue to improve methods of selection in breeding programs for production and associated traits. One possible solution is genome-wide marker-assisted selection (GWMAS). In brief, evenly-spaced genetic markers spanning the entire genome are genotyped (scored) on individuals to estimate their breeding value, which in theory could substantially increase the rate of genetic gain compared to traditional selection methods. To test the power of GWMAS, meat-type and egg-type chicken lines are being selected in parallel using either traditional (BLUP) or GWMAS. This year, after completing two rounds of selection, we conclude that compared to birds selected in parallel using current state-of-the-art breeding methods, genomic selection is superior for the vast majority of the traits selected including body weight and breast yield. This research strongly suggests that genomic selection is an improved breeding method. If costs for genetic testing continue to go down, then poultry breeders should be able to economically breed chickens faster using genomic selection and adapt more readily to changing consumer demands. The economic impact could be great since with 1 million meat-type birds processed per hour in the US alone, the net effect of even small improvements are large and worth millions of dollars. MAREK’S DISEASE Diagnosis, Surveillance and Pathotyping Marek’s disease virus (MDV) strains with similar mutation were isolated from chicken farms in Pennsylvania in 2007 and 2010. Affected farms ranged from 13-28 miles apart; the case involved different bird strains, vaccine companies, and pullet farm and hatchery origins. The isolated MDV strains were typed as vv+, but not unusually virulent. Mutation affects specificity of T65 monoclonal antibody for differentiating field strains from Rispens. We also diagnosed MD early mortality syndrome in Connecticut backyard flocks, demonstrating high potential virus load and need for vaccination even in backyard flocks. Peripheral neuropathy was also diagnosed in 6 week-old pullets in Ohio; the case involved low incidence of leg paralysis and the presence of lymphoplasmacytic neuritis and edema. Immunogenetics Understanding the relationship between host genetics and MD vaccine efficacy plays an important role in developing vaccination schemes for better control of the disease. Recently, chickens from two highly inbred lines (highly resistant and susceptible) and a series of 19 recombinant congenic strains were used to evaluate the protective efficacy of two commonly used MD vaccines and a candidate recombinant vaccine termed rMd5-Meq deleted vaccine. The protective indices of the vaccine ranked from high to low; the change in the ranking order of protective indices for two of the three vaccines between the two chicken lines indicated a vaccine X chicken line interaction affecting the vaccine protective efficacy. Marek’s disease virus immune evasion gene: MDVs retain the ability to evade immune recognition. Identifying and removing the viral genes that are responsible for virus immune evasion will produce a more effective vaccine. We have previously shown that MDV down-regulates MHC class I, a critical protein that signals the chicken’s immune system there is a virus infection, however, the gene (s) involved have not been identified. Recently, we demonstrated that an MDV gene, termed MDV012 is capable of reducing surface expression of MHC class I on chicken cells. Our results suggest that this is the first non-mammalian MHC class I immune evasion gene identified, and that it is highly conserved in herpesviruses. Cytokine and Chemokine Gene Expression Analysis in MDV Infection Through cytokine and chemokine gene expression analysis, we have discovered that vv+ strains of MDV drive the immune response to a