Heritability of pock counts and hatchability (fitness parameter) of chicks in highly productive layer lines infected as embryos by subgroup A and C Rous sarcoma virus*

Embryos (11-day-old) of White Leghorn strains (IWl, IWG and IWC) maintained at Central Avian Research Institute, Izatnagar by artificial insemination with one particular male to 4–7 females were inoculated via the chorioallantoic membrane (CAM) route with Rous sarcoma virus subgroup A [BS-RSV] and C [RSV(RAV-49)] of 0.2 ml (103pfu/ml) virus dose. The eggs were pedigree hatched for identification of corresponding CAMs of chicks. Pock counts were analyzed by least-square analysis (LSA). In the LSA of variance of pock counts, it was found that the sire effect was significant with subgroup A and subgroup C infection, indicating the pock count trait as a genetic trait. The estimate of heritability of pock counts varied widely from zero to 0.46 ± 0.22 with high standard error, indicating that either pock count is affected by several environmental factors such as inoculation procedure, virus doses etc. An overall reduction of hatchability of CAM-infected embryos occurred in three lines of this study. Therefore, the embryo infection by leukosis virus could influence the economy of poultry industry by severely affecting the fitness index in terms of hatchability. However, the ANOVA of percel:t hatchability within line and within pock count ranges was found to be non-significant to infection by virus of both subgroups, A and C, indicating that hatchability may not vary with line and with pock count ranges.