Genetic control of incubation behavior in the domestic hen

The genetic control of incubation behavior was investigated in the domestic hen by analysis of the incidence of the behavior in reciprocal crosses between nonbroody White Leghorn (WL) and broody Bantam (B) lines and in a backcross of F1 males (WL male x B female) and WL females. The hypothesis tested was that a sex-linked gene (or genes) plays a dominant role in the expression of incubation behavior. The incidence of incubation behavior was tested in hens held in floor pens with access to nests containing hard-boiled eggs during a 28-wk photoinduced laying cycle. The cycle was repeated if the behavior was not observed during the first cycle. The incidence of incubation behavior in B and WL hens was 78.6% (n = 28) and 0% (n = 28), respectively. Contrary to prediction, the incidence of incubation behavior in the WL male x B female and the B male x WL female crosses were not significantly different (61.6%, n = 73; and 56.8%, n = 37, respectively). The incidence of incubation behavior in the F1 backcross was 5.8% (n = 103), which was significantly less (P < 0.001) than predicted (39.3%). It was concluded that incubation behavior was not controlled by major genes on the Z chromosome. It was hypothesized that at least two dominant autosomal genes are involved, one causing and the other inhibiting the behavior with equal influence.