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Genetic loci inherited from hens lacking maternal behaviour both inhibit and paradoxically promote this behaviour.

Basheer A, Haley CS, Law A, Windsor D, Morrice D, Talbot R, Wilson PW, Sharp PJ, Dunn IC - Genet. Sel. Evol. (2015)

Bottom Line: 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).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.

View Article: PubMed Central - PubMed

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.

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.

No MeSH data available.


Related in: MedlinePlus

Percentage of hens that show complete incubation behaviour (incubation status trait class 1) in the founder SLK and WL breeds (F0) and in the F1 SLK × WL cross represented as a bar graph on the left hand of the graphic. On the right hand side of the graphic the cumulative incidence of incubation behaviour over the period of testing in the F2 population is represented as a line graph with the x-axis indicating weeks of age. At week 50 this is equivalent to the trait ‘incubation status’ class 1. For all data the y-axis represents the percentage of hens showing incubation behaviour (incubation status trait class 1)
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Fig1: Percentage of hens that show complete incubation behaviour (incubation status trait class 1) in the founder SLK and WL breeds (F0) and in the F1 SLK × WL cross represented as a bar graph on the left hand of the graphic. On the right hand side of the graphic the cumulative incidence of incubation behaviour over the period of testing in the F2 population is represented as a line graph with the x-axis indicating weeks of age. At week 50 this is equivalent to the trait ‘incubation status’ class 1. For all data the y-axis represents the percentage of hens showing incubation behaviour (incubation status trait class 1)

Mentions: Two divergent breeds of chicken, WL and SLK were used to set up the F2 cross used in this study. WL chickens were from a flock that is maintained at the Roslin Institute and showed no incubation behaviour (0 % incidence) when tested by the same method as that used to record phenotypes for the F2 population (Fig. 1). SLK chickens were obtained from the Wernlas Collection (Shropshire, SY7 9BL), a certified rare breeds farm (now closed), and maintained at the Roslin Institute. In this breed, incidence of incubation behaviour reached 90.5 % when tested (Fig. 1). All matings were performed by artificial insemination. Three WL sires were crossed with eight SLK dams and two SLK sires were crossed with ten WL dams in the F0 generation to produce the F1 cross. Four males and 20 females from the F1 generation were used to establish the F2 population. Phenotypic data for incubation behaviour were successfully recorded on 280 F2 animals from 19 families. This population was already used in a study that determined the causative mutation for preaxial polydactyly [17]. All animal experiments were performed according to United Kingdom Home Office legislation and were approved by the ethics review group of the Roslin Institute.


Genetic loci inherited from hens lacking maternal behaviour both inhibit and paradoxically promote this behaviour.

Basheer A, Haley CS, Law A, Windsor D, Morrice D, Talbot R, Wilson PW, Sharp PJ, Dunn IC - Genet. Sel. Evol. (2015)

Percentage of hens that show complete incubation behaviour (incubation status trait class 1) in the founder SLK and WL breeds (F0) and in the F1 SLK × WL cross represented as a bar graph on the left hand of the graphic. On the right hand side of the graphic the cumulative incidence of incubation behaviour over the period of testing in the F2 population is represented as a line graph with the x-axis indicating weeks of age. At week 50 this is equivalent to the trait ‘incubation status’ class 1. For all data the y-axis represents the percentage of hens showing incubation behaviour (incubation status trait class 1)
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4697313&req=5

Fig1: Percentage of hens that show complete incubation behaviour (incubation status trait class 1) in the founder SLK and WL breeds (F0) and in the F1 SLK × WL cross represented as a bar graph on the left hand of the graphic. On the right hand side of the graphic the cumulative incidence of incubation behaviour over the period of testing in the F2 population is represented as a line graph with the x-axis indicating weeks of age. At week 50 this is equivalent to the trait ‘incubation status’ class 1. For all data the y-axis represents the percentage of hens showing incubation behaviour (incubation status trait class 1)
Mentions: Two divergent breeds of chicken, WL and SLK were used to set up the F2 cross used in this study. WL chickens were from a flock that is maintained at the Roslin Institute and showed no incubation behaviour (0 % incidence) when tested by the same method as that used to record phenotypes for the F2 population (Fig. 1). SLK chickens were obtained from the Wernlas Collection (Shropshire, SY7 9BL), a certified rare breeds farm (now closed), and maintained at the Roslin Institute. In this breed, incidence of incubation behaviour reached 90.5 % when tested (Fig. 1). All matings were performed by artificial insemination. Three WL sires were crossed with eight SLK dams and two SLK sires were crossed with ten WL dams in the F0 generation to produce the F1 cross. Four males and 20 females from the F1 generation were used to establish the F2 population. Phenotypic data for incubation behaviour were successfully recorded on 280 F2 animals from 19 families. This population was already used in a study that determined the causative mutation for preaxial polydactyly [17]. All animal experiments were performed according to United Kingdom Home Office legislation and were approved by the ethics review group of the Roslin Institute.

Bottom Line: 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).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.

View Article: PubMed Central - PubMed

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.

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.

No MeSH data available.


Related in: MedlinePlus