الفهرس 
IntroductionOnly 14 pages are availabe for public view
 |  | from | 174 |  |  |
| | | from | 174 | | |
Abstract
This study aimed to achieve two goals. First, identify the single-locus and epistasis effects of 38,499 single-nucleotide polymorphism (SNP) markers on carcass, growth and fatty acids traits. Second, identify single nucleotide polymorphisms (SNPs) associated with beef fatty acid composition using RNA-Seq data. Phenotypic data were collected from 1,143 head of Angus bulls, steers and heifers. For the first goal, genomic DNA was isolated from meat samples and high-density SNP genotype results were obtained using the Illumina Bovine SNP50 beadarray. The results identified some candidate genes CGA, GLI3, DECR1, ALDOA, FTO, HPSE2 and CHST9 for carcass traits, LHX4 for birth weight and THRSP and FASN for fatty acids composition. A total of eleven SNP by SNP interaction were significantly (p < 0.135x10-10) associated with carcass traits. Five of these epistasis effects were associated with fat thickness, five with dressing percentage, and one with percent kidney, pelvic, and heart fat. For the second goal, total RNA was isolated from skeletal muscle samples of 10 purebred Angus animals. RNA-seq libraries were generated and sequenced to ~100bps on an Illumina GAIIX. Candidate genes were examined in an attempt to identify putative SNP. Seven SNPs identified in seven genes included: g.3202A>G (BPTF), g.260T>G (DDX5), g.1910T>G (FOXK2), g.1466A>G (VLDLR), g.207T>G (LPL), g.1568G>C (HEXDC) and g.12824T>G (UBR4). The g.3202A>G genotype was significantly associated with myristic acid (C14:0; P<0.0001), palmitic acid (16:0; P<0.0001), saturated fatty acids (SFA; P<0.0001), Atherogenic Index (AI; P<0.0001) and medium chain fatty acids (MCFA; P<0.0001). SNP g.260T>G and g.207T>G were significantly associated with docosahexaenoic acid (DHA) (C26:0 P<0.0001). Also, there was a significant association between the g.260T>G, g.1910T>G and g.12824T>G SNPs and tridecylic acid (C13:0; P<0.0001). There was no association between g.1568G>C SNPs and any fatty acid composition traits. In conclusion, the SNPs g.3202A>G, g.260T>G, g.1910T>G, g.1466A>G, g.207T>G and g.12824T>G may be viable markers useful for selecting animals that have a healthier fatty acid composition in Angus beef cattle.
Keywords: beef cattle, carcass traits, fatty acid composition, RNAseq, genome-wide association study, marker-assisted selection, single nucleotide polymorphism.