Genetics of broodiness in poultry — a review

In poultry, the selection against broodiness took up presumably naturally occurred mutations in the White Leghorn breed and led to an almost complete loss of the avian form of parental behaviour (incubation of eggs). Early studies on the genetics of broodiness demonstrated that the trait is polygenic with a major sex-linked effect. The reassessment of the studies on putative genes located on the Z chromosome, which are implicated in the control of broodiness, has resulted in the denial of this hypothesis. The recent experiments bear witness that incubation behaviour in chickens is not controlled by a major gene (or genes) on Z chromosome and there must, therefore, be major autosomal genes contributing to the expression of the behaviour. If a broody gene does exist on the Z chromosome it is one of at least three genes including two dominant autosomal genes, one causing and other one inhibiting incubation behaviour, with probably equal influence.