35 - Detecting Effective Starting Point of Genomic Selection by Divergent Trends from BLUP and Ssgblup

Genomic selection has been adopted nationally and internationally in different livestock and plant species. However, understanding whether genomic selection has been effective or not is an essential question for both industry and academia. Once genomic evaluation started being used, estimation of breeding values with pedigree BLUP became biased because this method does not consider selection using genomic information. Hence, the point of divergence of genetic trends obtained with BLUP and Single-step genomic BLUP (ssGBLUP) may indicate the start date of genomic selection. This study aimed to find the start date of genomic selection for a set of economically important traits in pigs and Angus cattle by comparing genetic and Realized Mendelian sampling (RMS) trends obtained using BLUP and ssGBLUP. In pigs, the genetic trends from ssGBLUP and BLUP diverged for all traits with different intensity. In beef cattle, the trends started diverging in 2009 for weaning weight and in 2016 for postweaning gain, with little divergence for birth weight. In pigs, the RMS trends from ssGBLUP and BLUP diverged strongly for one trait and weakly for another trait. In beef cattle, the RMS trends started diverging in 2009 for weaning weight and in 2016 for postweaning gain, with little trend for birth weight. Divergence of the genetic trends from ssGBLUP and BLUP indicate onset of the genomic selection. Presence of trends for RMS indicates selective genotyping, with or without the genomic selection. The onset of genomic selection and genotyping strategies agree with industry practices across the two species. In summary, the effective start of genomic selection can be detected by the divergence between genetic and RMS trends from BLUP and ssGBLUP.