Effects of domestication related genes on behaviour, physiology and gene expression in chickens

Abstract

Till minnet av min älskade vän. I tanken, i skrattet, i hjärtat. För alltid.Abstract Domestication, the process when animals adapt to captivity, tends to modify a whole array of traits towards what has been termed "the domesticated phenotype", where the domesticated animal differs from its wild ancestor in morphology, physiology, development and behaviour. Physiological traits and behaviours are controlled by genes. One single gene can control several different traits (pleiotropy), be linked to a neighbouring gene on the chromosome, or interact with another gene that in turn controls another trait. This is the explanation why one can select for high egg production and at the same time get a change in the colour of the plumage. The aim of this thesis was to evaluate the effect of a mutation in two particular genes (PMEL17 and TSHR) related to domestication on behaviour, gene expression and other physiologial traits. The animals investigated were chickens from a cross between the ancestral Red Junglefowl (RJF) and the domesticated White Leghorn (WL) selected for high egg production traits. PMEL17 is a gene affecting plumage colour. A mutation in the gene causes a non-pigmented white plumage and has been shown to protect against feather pecking. Our studies showed that a mutation in the PMEL17 gene affects social, explorative and aggressive behaviour in chickens, but not visual ability. The thyroid stimulating hormone receptor (TSHR) plays an important role in the signal transduction of the hypothalamus-pituitary-thyroid axis that has general effects on development, behaviour and reproduction. A mutation in the TSHR gene affects incubation time, domestication related behaviours such as fear and aggression, gene expression, thyroid hormone levels and photoperiodic reproduction responses in chicken. The results from this thesis suggest that a mutation in the PMEL17 and TSHR genes have pleiotropic effects on behaviour and traits related to domestication, and it is therefore likely that both genes have been important for the domestication of the chicken. Populärvetenskaplig sammanfattning

Utilization and Conservation of Landrace Chickens of Nigeria: Physical and Performance Characteristics, Issues and Concerns

“…The typical free range IC closely approximates the wild type (Red jungle fowl) plumage phenotype (most likely genotype) and is sexually dimorphic in plumage color; hens being more ground colored than roosters [30]. A significant deviation of today's ICs from the classical phenotype is expected owing to centuries of migration, natural selection (including predation mostly directed at chickens having brightly colored plumage), negative selection to fulfill cultural and ritual roles, intensification of production and artificial selection by man (increasing expression of the 'domesticated phenotype') [31,32], and interbreeding between phenotypes (also genotypes). Consequently, plumage color phenotypes reported for adult NICs range from full ground color to full black color.…”

“…Consequently, plumage color phenotypes reported for adult NICs range from full ground color to full black color. Findings however, vary by source of samples (on-farm vs. market samples), system of production (intensive vs. semi-intensive vs. extensive) due to differences in flock structure (male:female; adult:grower), and environmental effects on plumage genotype and phenotype [32]. In heavy ecotype (HE) ICs, [33] reported plumage color as white, white and black, gold and black, black, barred, brown, brown and black, gold, and gold and brown.…”

Benefits of Farm Animals Genetic Adaptation: A Review

“…Consequently, genetic selection has got an attention to establish breeds which are more adapted, fast growing, productive and better disease and insect infestation resistant animals for supplying food and other livestock products to human beings in every parts of the world [3]. However, evidence for genetic adaptation in farm animals remains poorly understood [4].…”