Effect of tumor virus susceptibility alleles on the late-feathering gene K on early growth of White Leghorns

The influence of tumor virus susceptibility (tvb) alleles and the sex-linked, late-feathering-endogenous virus 21 complex (K-ev21) on early growth was observed in progeny from late-feathering (LF) and early-feathering (EF) dams. At 2, 4, 6 and 10 wk of age, homozygous (K/K) males that carried a dominant tvb(s1) allele were significantly (P 0.05) lighter in total body weight than K/K homozygous endogenous virus (EV) EV21-resistant (tvb(r)/tvb(r)) hatchmates. Among heterozygous (K/k+) males, tvb(s1) did not significantly influence growth when compared with tvb(r)/tvb(r) hatchmates. At 10 wk of age, tvb(s1)-positive K/w female progeny from LF dams were also significantly lighter than tvb(r)/tvb(r) K/w hatchmates. However, among progeny from EF dams no significant within sex differences in body weight were found regardless of their feather or EV susceptibility phenotype. Results indicate that susceptibility to EV21 infection is particularly detrimental to early growth of ev21-K homozygous male and hemizygous female progeny of LF dams