Thyroid hormones are well known important to be in development and growth in birds and that signaling of thyrotropin (TSH) regulates the photo induced seasonal reproduction. A mutation at the thyroid stimulating hormone receptor (TSHR) gene in domestic breeds of chicken could be involved in the release of the photoperiodic regulation. Furthermore, TSH can affect a wide range of domestication related phenotypes, such as behaviour, growth rate and pigmentation. The aim of this study was to investigate the behaviours expressed in the different genotypes on the TSHR gene in chickens. Four standard tests were conducted, aerial predator, fear of human, social dominance and tonic immobility. An advanced intercross line of chickens between red junglefowl and White leghorn was used. Male domestic type chickens explored more, showed more less fear behaviours and showed least fear behaviours in the fear of human test. Increased activity and flight response has been interpreted as a lower fear response, which is in line with this study. The wild type chickens showed more social dominance than domestic type chickens which are in line with previous results. In tonic immobility there was a difference between the wild type male and heterozygous male chickens in latency until first head movement. The conclusion of this study is that there is a difference between the wild type and domestic type chickens. This indicates that the TSHR gene is involved in behavioural changes during domestication, but whether it is due to passive or active selection is the question.

It has been shown that thyroid hormones are important in development and growth in birds and further that thyrotropin (TSH) signaling regulated photoinduced seasonal reproduction. In addition to controlling the development of certain physiological traits, TSH can affect a wide range of phenotypes related to domestication such as behaviour, growth rate, more frequent reproductive cycle’s, pigmentation and also behaviour. Studies indicate that thyroid hormone physiology could potentially be responsible for differences in individual stress response as well as differences in social dominance. This project investigated behaviours expressed in the different genotypes on the Thyroid stimulating hormone receptor (TSHR) gene in chickens. Standard test such as Fear of human, Aerial predator, Tonic immobility and Social hierarchy were carried out with White leghorn (WL) as a domesticated species and Red Junglefowl (Rjf) as their wild counterpart; these were considered to be the control group. There was no significant result on genotype effect for the TSHR animals observed in those variables tested. The TSHR mutants were expected to mirror the White leghorn behavioural response and the TSHR wildtype the behaviour of Rjf. This was however not confirmed. There were a significant interaction between genotype effect and sex effect for TSHR for stand alert in the Aerial predator test which mirrored the results seen in the control groups. The male wildtype followed the male Rjf pattern however the mutant did not mirror the WL male. This study would benefit from more individuals to be tested, for stronger statistical results, plus also to have all genotypes represented to fully investigate the affect the TSHR mutation have on domesticated chickens and potentially the domestication process in a range of species. / TSHR