Genomics and New Approaches to Study Complex Traits in Pigs and Other Livestock Species. A Focus on the Investigation of Gene Networks Related to Fat Quality and Deposition in Pigs and Preliminary Research to Study Factors Related to Performances in Piglets and Poultry

The recent development of new technologies and the progress of genetics and genomics have opened new horizons in breeding programs. Genomic selection has been successfully applied to dairy cattle breeding schemes, but had a limited success in other livestock species, such as pigs and chickens. Anyway, the technological advances seen in the last years may represent important tools for the deciphering of complex traits, for which traditional selection has been slowly accelerating. The studies reported in the present thesis are addressed towards the application of different OMICs technologies to the analysis of productive traits in livestock species. The study was mainly focused on the investigation of candidate genes and gene networks associated to porcine fatness traits using genomics, transcriptomics and single gene studies. The results confirmed the important role that ELOVL elongase 6 gene region plays in backfat fatty acid composition, and reported associations between markers on Perilipin genes and fatness traits. Furthermore, a transcriptome analysis performed on backfat samples of pigs divergent for backfat thickness highlighted several expression patterns related to adipose tissue deposition and suggested that Perilipin 2 gene may play an important role in adipose tissue deposition. OMICs technologies were also applied in two preliminary studies performed with the aim of identifying factors and genetic causes involved in variations in pig colostrum metabolome and in the occurrence of myopathy-like defects in breast muscle of broiler chickens. On the whole, the application of genomics, transcriptomics and metabolomics showed to be an effective tool for the study of complex traits in different livestock species, and for the detection of genes involved in phenotypic variations. Further studies are needed, but the found evidences contribute to increase the knowledge about markers useful for the genetic improvement of complex polygenic traits.