National Program for Genetic Improvement of Feed Efficiency in Beef Cattle

Genomic selection offers the opportunity to improve the feed efficiency of beef cattle, however, to be effective, models to obtain molecular estimates of breeding value (MEBV) must be trained in populations that are representative of the breeds in which selection is to be implemented. To address this, we have collected Illumina HD or BovineSNP50 genotypes on 4,864 individually fed animals from 5 breeds (476 Hereford, 37 Limousin, 1,778 Angus, 155 Red Angus x Angus, 2,455 Simmental x Angus) which have been analyzed under Bayesian models for the identification of QTLs and generation of MEBV prediction equations. An additional 1,008 Charolais, Hereford, Gelbvieh x Angus, Angus and Wagyu animals are currently being genotyped. Moreover, MEBV accuracies will progressively decrease in subsequent generations if associated markers rather than causal mutations are used, unless additional phenotypes are collected and the MEBV prediction models are retrained. To address this, we will identify QTL of large effect and attempt to find causal mutations by combining RNA-seq, Gene Set Enrichment and whole genome re-sequencing analyses using animals with extreme RFI phenotypes.  Five tissues (Small Intestine, Liver, Pituitary, Skeletal Muscle and Hypothalamus) collected on each of 12 Angus and 12 Simmental x Angus (6 high and 6 low RFI in each breed) are currently being analyzed for gene expression. In addition, methane output and nutritional experiments are underway to evaluate relationships between greenhouse gas emissions and feed efficiency and the influence of diet energy concentration on efficiency.