Studies on Genetic Resistance to Marek's Disease

Abstract

The feasibility of selecting for genetic control of mortality from diseases of the avian leukosis complex, include what is now considered as Marek's disease, has been amply demonstrated (1,4). For selection to be effective, however, the stock under test must be adequately exposed to the disease agents concerned and must demonstrate a level of mortality which will permit differentiation among sire and dam families. The level of natural exposure cannot be assured in advance, and in fact will vary greatly from time to time. The use, as a control, of a specially selected susceptible strain, such as the Cornell S strain (3), will serve as a monitor of the existing level of exposure and will aid in maintaining the disease on the breeding or testing farm.