Resistance to Marek's disease observed among sire families and inbred lines.

Abstract

Synopsis Experiments were conducted to study sire family variation and variation among inbred lines in resistance to Marek's disease (MD). In three experiments chicks were challenged at 1 or 21 d of age with the BC‐1 isolate of MD virus and the post‐challenge test period was approximately 56 d. In a fourth experiment chickens were reared for 147 d at a field station where they were exposed to MD‐infected birds. Sire families within each of the two strains studied, which had been selected for hen‐housed egg production, were quite heterogeneous for resistance to MD and incidence ranged from 0 to 45.8%. The ranking of these sire families for incidence of MD did not correlate with ranking of sires for economically important traits measured in their sisters. MD among inbred lines in a 54‐d experiment ranged from o to 88.9% and in a 147‐d field experiment from 0 to 50%. In neither experiment was the inbreeding coefficient of inbred lines correlated with incidence of MD.