EFFECT OF SELECTION FOR HIGH EGG-PRODUCTION IN CHICKENS ON SHEDDING OF LYMPHOID LEUKOSIS VIRUS AND GS-ANTIGEN INTO EGGS

Lymphoid leukosis virus (LLV) and group specific (gs) viral antigen were detected less frequently in albumen of eggs from two strains of Single Comb White Leghorns that had been selected for high egg production than in corresponding random-bred control strains, which represented the original base population. In a third selected strain, for which no comparable control strain was available, the frequency with which LLV and gs antigen were detected was similar to the other two selected strains. The greatest contrast was between selected Strain 1 and control Strain 5 in which the percentage of eggs with LLV in albumen was 1.4 and 21.4, respectively, and the percentage with gs antigen was 1.2 and 19.9. These differences between control and selected strains of chickens were not related to genetic cellular resistance to virus infection, because inoculation of chorioallantoic membranes with Rous sarcoma virus of subgroups A and B revealed that the proportion of birds resistant to subgroups A and B viruses was not greater in the selected strains than in the control strains.