Detection of QTLs in angus beef cattle on chromosomes 2 and 11 affecting growth and carcass traits

Abstract

Mapping quantitative trait loci (QTL) using genetic markers is the first step in implementing marker assisted selection programs. Microsatellite loci and polymerase chain reaction-restriction fragment length polymorphisms (PCR-RFLP) were used as genetic markers for QTL affecting carcass traits: hot carcass weight (HCW), 12th rib fat thickness (FT), kidney, pelvic and heart fat (KPH) percentage, marbling score (MB), quality grade (QG), ribye area (REA) and yield grade (YG) and growth traits: weaning weight (WW) and yearling weight (YW). Phenotypic data were collected on seven Angus half-sib family groups with an average of 28 progeny per sire. DNA extracted from ear tissue samples was used evaluate nine microsatellites covering a 40 centimorgan (cM) region on chromosome 2, and thirteen microsatellite markers and one PCR-RFLP spanning 38 cM on chromosome 11. Each sire was heterozygous for an average of 4 markers for each chromosome. Data were analyzed by family with the interval-mapping program, ANIMAP. The results revealed that the region on chromosome 2 flanked by the microsatellite loci BM2808 and RM041 were strongly associated with KPH percentage (total LOD = 5.81) with an effect of about 1.5 phenotypic standard deviation in one family. Markers BMS2872 (46 cM), BMS2024 (55 cM), and BMS1126 (56.3 cM) on chromosome 2 tend to be associated with REA, HCW, and YW (total LOD of 2.8, 3.75 and 2.5). Regions nearby BMS989 (85.4 cM), BMS2208 (113.2 cM), and HEL 13 (114.5 cM) on chromosome 11 indicate linkage associated with KPH, FT and MB respectively (total LODs of 3.56, 3.1, and 2.54). All these marker-linked QTLs had an estimated effect more than .75 phenotypic standard deviation. These findings show that there are several chromosome regions associated with carcass traits in beef and demonstrate the power of genetic linkage analysis to detect these regions even in small families.