Genome-Wide Association Study of Dry Matter Intake, Metabolic Weight, Growth and Feed Efficiency in Beef Cattle

Feed costs make up the majority of beef production costs. The objectives of this study were to map quantitative trait loci (QTL) associated with output and input traits, namely average daily gain (ADG), dry matter intake (DMI), mid-test metabolic body weight (MBW), and feedlot residual feed intake (RFI) using 4 different beef cattle populations. A Bayes-B model was used to analyze all HD (Angus, Hereford, Simmental) or 50K SNP markers (admixed) simultaneously. The QTL were identified by characterizing the proportion of variation explained by non-overlapping 1-Mb genomic regions. Some 5, 9, 22 and 13 significant 1-Mb SNP windows distributed over 5, 7, 12 and 10 different chromosomes were detected for ADG, DMI, MBW and RFI traits. The identified QTLs had little overlap across the populations. The largest 1-Mb SNP window for ADG was on BTA7 at 93^rd Mb in Hereford cattle, explaining 9.18% genetic variance.  The 1-Mb SNP window located on BTA7 at 23^rd Mb was the largest for DMI and MBW explaining 10.39% and 14.24% genetic variance in Angus cattle. Four different QTLs (BTA6 at 50^th Mb, BTA14 at 43^rd Mb, BTA15 at 82^nd Mb and BTA20 at 4^th Mb) explaining less than 3% of genetic variance were identified as the largest QTL associated with RFI in Angus, USMARC Cycle VII-F1^2, Simmental and Hereford populations, respectively. Further investigations are needed to identify causal variants harbored within the identified 1-Mb windows. Once found, knowledge of such mutations would create new opportunities for selection of productive, efficient animals.