title: Genetic loci inherited from hens lacking maternal behaviour both inhibit and paradoxically promote this behaviour.
abstract: BACKGROUND
  A major step towards the success of chickens as a domesticated species was the separation between maternal care and reproduction. Artificial incubation replaced the natural maternal behaviour of incubation and, thus, in certain breeds, it became possible to breed chickens with persistent egg production and no incubation behaviour; a typical example is the White Leghorn strain. Conversely, some strains, such as the Silkie breed, are prized for their maternal behaviour and their willingness to incubate eggs. This is often colloquially known as broodiness.
  
  
  RESULTS
  Using an F2 linkage mapping approach and a cross between White Leghorn and Silkie chicken breeds, we have mapped, for the first time, genetic loci that affect maternal behaviour on chromosomes 1, 5, 8, 13, 18 and 19 and linkage group E22C19W28. Paradoxically, heterozygous and White Leghorn homozygous genotypes were associated with an increased incidence of incubation behaviour, which exceeded that of the Silkie homozygotes for most loci. In such cases, it is likely that the loci involved are associated with increased egg production. Increased egg production increases the probability of incubation behaviour occurring because egg laying must precede incubation. For the loci on chromosomes 8 and 1, alleles from the Silkie breed promote incubation behaviour and influence maternal behaviour (these explain 12 and 26% of the phenotypic difference between the two founder breeds, respectively).
  
  
  CONCLUSIONS
  The over-dominant locus on chromosome 5 coincides with the strongest selective sweep reported in chickens and together with the loci on chromosomes 1 and 8, they include genes of the thyrotrophic axis. This suggests that thyroid hormones may play a critical role in the loss of incubation behaviour and the improved egg laying behaviour of the White Leghorn breed. Our findings support the view that loss of maternal incubation behaviour in the White Leghorn breed is the result of selection for fertility and egg laying persistency and against maternal incubation behaviour.
authors.affiliation: Roslin Institute and Royal (Dick) School of Veterinary Studies, University of Edinburgh Easter Bush, Midlothian, EH25 9RG, Scotland, UK. atia.basheer@uvas.edu.pk.|Animal Breeding and Genetics Section, Department of Livestock Production, University of Veterinary and Animal Sciences, Ravi campus, Lahore, Pakistan. atia.basheer@uvas.edu.pk.
authors.forename: Atia
authors.initials: A
authors.lastname: Basheer
authors.affiliation: Roslin Institute and Royal (Dick) School of Veterinary Studies, University of Edinburgh Easter Bush, Midlothian, EH25 9RG, Scotland, UK. chris.haley@roslin.ed.ac.uk.
authors.forename: Chris S
authors.initials: CS
authors.lastname: Haley
authors.affiliation: Roslin Institute and Royal (Dick) School of Veterinary Studies, University of Edinburgh Easter Bush, Midlothian, EH25 9RG, Scotland, UK. andy.law@roslin.ed.ac.uk.
authors.forename: Andy
authors.initials: A
authors.lastname: Law
authors.affiliation: Roslin Institute and Royal (Dick) School of Veterinary Studies, University of Edinburgh Easter Bush, Midlothian, EH25 9RG, Scotland, UK. dawn.windsor@roslin.ed.ac.uk.
authors.forename: Dawn
authors.initials: D
authors.lastname: Windsor
authors.affiliation: Roslin Institute and Royal (Dick) School of Veterinary Studies, University of Edinburgh Easter Bush, Midlothian, EH25 9RG, Scotland, UK. david.morrice@roslin.ed.ac.uk.|Edinburgh Genomics, Ashworth Laboratories, The University of Edinburgh, Edinburgh, EH9 3JT, UK. david.morrice@roslin.ed.ac.uk.
authors.forename: David
authors.initials: D
authors.lastname: Morrice
authors.affiliation: Roslin Institute and Royal (Dick) School of Veterinary Studies, University of Edinburgh Easter Bush, Midlothian, EH25 9RG, Scotland, UK. richard.talbot@roslin.ed.ac.uk.|Edinburgh Genomics, Ashworth Laboratories, The University of Edinburgh, Edinburgh, EH9 3JT, UK. richard.talbot@roslin.ed.ac.uk.
authors.forename: Richard
authors.initials: R
authors.lastname: Talbot
authors.affiliation: Roslin Institute and Royal (Dick) School of Veterinary Studies, University of Edinburgh Easter Bush, Midlothian, EH25 9RG, Scotland, UK. peter.wilson@roslin.ed.ac.uk.
authors.forename: Peter W
authors.initials: PW
authors.lastname: Wilson
authors.affiliation: Roslin Institute and Royal (Dick) School of Veterinary Studies, University of Edinburgh Easter Bush, Midlothian, EH25 9RG, Scotland, UK. peter.sharp@roslin.ed.ac.uk.
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Sharp
authors.affiliation: Roslin Institute and Royal (Dick) School of Veterinary Studies, University of Edinburgh Easter Bush, Midlothian, EH25 9RG, Scotland, UK. ian.dunn@roslin.ed.ac.uk.
authors.forename: Ian C
authors.initials: IC
authors.lastname: Dunn
mesh_terms: D000818:Animals; D001522:Behavior, Animal / Q000502:physiology*; D002645:Chickens / Q000235:genetics* / Q000502:physiology; D002874:Chromosome Mapping; D003433:Crosses, Genetic; D004531:Eggs; D005260:Female; D060005:Genotyping Techniques; D008425:Maternal Behavior / Q000502:physiology*; D020641:Polymorphism, Single Nucleotide; D040641:Quantitative Trait Loci