Data were collected on egg production, livability, lymphoid leukosis virus and antibody incidence, and hemagglutinin response to sheep red blood cells for slow- and fast-feathering female progeny from slow- and fast-feathering dams with known lymphoid leukosis virus infection status. Analyses of these results indicate that when the offspring or the dams are of the slow-feathering type, the offspring experience an increased rate of horizontal infection. This infection seemingly leads to an immunologically tolerant condition with an inability to produce specific lymphoid leukosis virus antibodies, thereby allowing the viremia to persist. This immunologically tolerant condition, which also occurs in the progeny of virus positive dams due to congenital transmission, is associated with depressed egg production performance. However, a hypothesized lack of immunological competence was not found in the hemagglutinin response to sheep red blood cells late in life. Our results suggest that fast-feathering progeny of slow-feathering dams may also be adversely influenced by increased congenital infection from their dams.

A device was developed for the nondestructive measure of body volume by air displacement. Two experiments were performed on Coturnix quail to determine the feasibility of using body density and volume of the live bird as criteria of selection for changing whole body lipid content. In Experiment 1,423 birds were used from three selected lines differing in adult weight. Three measurements of volume were taken on each bird. Repeatability of volume was consistently high for all line-sex subclasses, averaging .75. A phenotypic correlation of .55 was derived for body density and lipid content of the whole carcass. Estimates of heritabilities and genetic relationships for body density, volume and weight, and whole body lipid content were derived in Experiment 2 on 739 birds representing 50 sires and 125 dams of a randombred population. Heritability of volume averaged over full and half-sibs and over sexes was high (.66). The average genetic correlation for volume and lipid content was .44. Heritabilities of density averaged .38 and were highly genetically correlated (.69) with lipid content, which had an average heritability of .35. Body weight was very highly heritable in the population (.82) and correlated genetically with body lipid (.60).

No abstract