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UBC Theses and Dissertations

A molecular genetic survey of immune response genes and biodiversity of industrial and non-industrial chickens Izadi Shavakand, Fariba


The current practices in industrial poultry breeding developed specialized production lines from very few breeds, resulting in reducting in genetic diversity. “Free run/free range” production systems (non-industrial) are a more recent trend in the poultry sector. Non-industrial chicken populations may differ genetically and have more diversity in disease resistance genes than industrial populations. To test this hypothesis, six chicken populations from non-industrial source; Silkies (SK), Taiwanese Cross (TC), Shiqi (SQ), Yellow Shiqi (YSQ), Yellow Wai-Chow (YW), and Agassiz Cross (AC), and industrial populations; Lohmann White (LW) and Lohmann Brown (LB), were sampled and three related experiments were carried out. First, I used 18 microsatellite markers to study genetic diversity within and among the chicken populations. The industrial population LB and the experimental cross AC which shared some common ancestors, were closely related. Non-industrial chickens SK and TC, with Chinese breed ancestry, were related to SQ, YSQ and YW. LW with White Leghorn ancestry, was not related to the non-industrial populations. Except for YSQ and SQ, STRUCTURE clustered these chicken populations to the genetically distinct groups. Secondly, I used microsatellite marker (LEI0258), situated within the Major Histocompatibility Complex (MHC) region, to reflect the genetic variability of the adaptive immune system. Results indicated that the industrial chicken populations may have less genetic variability in the MHC compared to non-industrial populations but industrial populations may have higher frequency of certain alleles that were part of their selection history against specific pathogens. Finally, I used SNP markers to examine the genetic variation in candidate genes associated with the innate immune system (ChB6, Casp-1, IAP-1, TGF-β3, BMP-7, TLR4, MD-2, IFN-γ, iNOS, IL-2, Mx1, and TVB). There was no difference between industrial and non-industrial populations in genetic variability in this immune system. The results provided partial support for the hypothesis that industrial populations may have higher resistance to specific diseases, while non-industrial populations may have higher general disease resistance. In conclusion, the results of this thesis research provided information on the genetic diversity of these chicken populations that can be used in decision making on conservation and in developing breeding stocks for free run/free range production.

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