The use of genomics for improving livestock production

[摘要] The goal of the study was to examine ways in which molecular genetics can be used toenhance the performance and sustainability of beef cattle production. A review of theliterature of livestock and poultry was included to describe different approachespreviously used for quantitative trait loci (QTL) studies, followed by two case studies.The first case study was to detect QTLs that affect relative amounts of saturated (SFA),monounsaturated (MUFA) and polyunsaturated (PUFA) fatty acids using 328 F2 progenyof Wagyu x Limousin F1 derived from eight Wagyu founder bulls. The search wasimplemented with 217 markers covering the 29 bovine autosomes. A total of six QTLswere found which are located on five different chromosomes; on a genome-wide basistwo were statistical significant and four were suggestive QTLs. On BT A2, a QTL wasfound that had additive effects on SFA (4 cM, F = 10.07, P = 0.04), MUFA (4 cM, F =23.62, P < 0.01) and PUFA (11 cM, F = 20.74, P < 0.01). Two QTLs with dominanceeffects on MUFA were observed on BTA9 (P = 0.04; 2 QTL vs. I QTL). Threeadditional suggestive QTLs for dominant effects on the relative amounts of fatty acidswere also detected. A QTL affecting the PUF A content were observed at 31 cM onBTAIO (F = 9.22; P = 0.06) and at 12 cM on BTA15 (F = 9.67, P = 0.06). Finally, aQTL affecting the MUFA content was found at 47 cM on BTA22 (F = 9.62, P= 0.08). Asecond case study included an experimental data that was analyzed and divided into twocomponents: I) to validate the pedigree expectation of genomic contributions tosuccessive generations of backcrossing at loci unlinked to the locus being introgressed;and 2) to examine the effectiveness of the introgression strategy. Experimentally,backcrossing a self coat colour pattern into Line I Hereford was attempted. The twofounder populations, Fl cross, two subsequent generations of backcrossing, and anintercross generation were evaluated. In total 526 were genotyped using 34 unlinked andfive linked microsatellite markers. Estimated contributions of Line I Hereford in the Fi,B1 and B2 generations were 0.500, 0.750, and 0.875, compared to expected contributionsbased on a pedigree of 0.540, 0.746, and 0.819. In this study, the introgression wascompromised because the linked markers used did not sufficiently segregate between thefounder populations however more markers will be required for further research. Finally,to integrate the knowledge gained in the preceding studies, an experiment was designedto identify QTLs that have effect on tick resistance, carcass weight and carcass quality inNguni and Angus cattle using the F2 design. If successful, the results of this study mightlead to use of marker assisted introgression to increase resistance to tick of South AfricanAngus and (or) add value to the carcass quality and carcass weight to Nguni.

[发布机构] University of the Free State