The Effect of Diet on Mortality Attributed to Marek’s Disease Among Leghorn Genotypes

HIGH mortality is frequently associated with the natural occurrence of Marek’s disease in poultry flocks (Kottaridis, 1969). Environmental treatments which contribute to the severity of this disease are, therefore, of considerable biological and economic importance. A natural outbreak of Marek’s disease occurred in an experimental population consisting of five commercial strains of Leghorns reared on two different diets under two light regimes. This provided the opportunity to evaluate the genotypic, environmental and interrelated effects on mortality resulting from this disease. MATERIALS AND METHODS In February, 1968, 1,440 hatching eggs were secured from each of five commercial Leghorn strains for use in this experiment which was conducted from 0 to 329 days of age. The brooder-rearing house and laying house each consisted of 40 pens as described by Proudfoot and Gowe (1967). Chicks from each strain were randomly housed in separate pens with each pen initially housing 65 female chicks. The…