MODE OF INHERITANCE OF UNSELECTED TRAITS IN LINES OF CHICKENS SELECTED FOR HIGH OR LOW ANTIBODY-RESPONSE TO SHEEP RED-BLOOD-CELLS - 1 - RESISTANCE TO MARBLE SPLEEN DISEASE VIRUS AND JUVENILE BODY-WEIGHT

Two lines of White Leghorns that had undergone long-term selection for high (HH) or low (LL) antibody response to sheep red blood cell antig en(s) formed the nuclear lines for this experiment. Matings were made in a full diallel cross to produce in a single hatch from age-contempo rary breeders the parental lines, reciprocal F-1 and F-2 crosses, and backcrosses for 16 progeny types. For males and females, there were pa rental line differences in BW to 42 d of age, after which there was a decline between lines for males. Differences in BW between reciprocal F-1 crosses and maternal heterosis declined with age, primarily reflec ting dissipation of effects of egg weight. Heterosis of BW was depende nt on the particular F-1 cross and recombination effects were not impo rtant. At 50 d of age chicks were inoculated with either a 1 or 10% su spension of spleen extract from chickens infected with marble spleen d isease virus (MSDV). A third group served as uninjected controls. Resp onse to MSDV was evaluated by spleen weight 6 d after inoculation. Spl een weights relative to BW of control chicks were heavier for the HH t han LL line with evidence from the crosses of sex-linkage and negative heterosis. Line LL chicks were more resistant to MSDV than Line WH ch icks with F-1 crosses intermediate to and different from either parent al line with no evidence of heterosis.