Relationship between egg size and subgroup J avian leukosis virus in eggs from broiler breeders

Hatching eggs from three broiler breeder flocks that had experienced losses from myeloid leukosis were tested for infection with avian leukosis virus of subgroup J (ALV-J). Sufficient eggs were positive in two flocks to relate infection to egg weight. Allantoic fluid, embryonic tissue and yolk were collected after 18 days of incubation. The albumen and allantoic fluid were tested by enzyme-linked immunosorbent assay (ELISA) for group-specific (gs) antigen and all specimens were inoculated onto cell cultures to test for virus by immunofluorescence assay. Virus detected was identified as ALV-J by polymerase chain reaction techniques. The percentage of eggs that tested positive for gs antigen and virus was higher in those that weighed under 60 g than in heavier eggs (P < 0.01). In one flock, antibody to ALV-J was detected by ELISA in yolk from 14 and 43% of the eggs that tested positive or negative for virus, respectively. Testing the same eggs for antigen, virus and antibody should be useful for establishing the status of infection of the hens.