Complete endogenous RNA tumour virus production by inbred and non-inbred chickens.

Nine- to 11-day embryos of five outbred and 12 inbred stocks were assayed for complete endogenous subgroup E virus. About one-third of the embryos produced a subgroup E virus. The percent virus production was higher in the inbred than in the outbred embryos, but wide variation among the inbred lines suggested that this was a chance phenomenon and probably not due to inbreeding per se. There was a reduced incidence of subgroup E virus production in the strains selected for economic traits when compared with the incidence in the corresponding random-bred control stocks. Further experimental work is required to determine if this trend is a real and not a chance phenomenon.