294 Increased fluctuations of genetic evaluations with genomic information. (30th November 2020)

• Record Type: Journal Article
• Authors: Lourenco, Daniela; Tsuruta, Shogo; Hidalgo, Jorge; Misztal, Ignacy
• Is Part Of: Journal of animal science. Volume 98(2020)Supplement 4
• Page Start: 32
• Page End: 33
• Publication Date: 2020-11-30
• Subjects: GEBV changes Genomic relationship matrix Outliers; Livestock -- Periodicals; Livestock; Electronic journals; Periodicals; 636.005
• DOI: 10.1093/jas/skaa278.058
• Languages: English
• ISSNs: 0021-8812

Abstract

Abstract: Under traditional BLUP, animals without new data in subsequent evaluations had stable EBV even when its precision was low. However, changes in EBV could still be observed for some animals when fixed effects were redefined, independently of accuracy levels. Given no model changes were made, the high stability of BLUP generated great confidence in the method. With the adoption of genomic evaluations by the livestock industry and the accumulation of genotypes, changes in genomic EBV (GEBV) in subsequent evaluations are being frequently reported; this is true even for animals that have no added phenotypes. Consequently, there are questions about why such changes happen. The main cause is the increase in connectivity among animals. As genomic relationships consider alleles that are identical by state, all genotyped animals can have some level of relationships, even though they do not share common ancestors in the current population. In this way, phenotypes added for a portion of the genotyped animals in the evaluation will be shared among nearly all genotyped animals. Conversely, in BLUP, those phenotypes are shared only with relatives in the pedigree; therefore, fewer changes are observed. Besides the increased connectivity, changes in blending and scaling of the genomic relationship matrix can cause changes in subsequent GEBV. Using real livestock data, we observed average changes of 0.1 additive genetic standard deviation (SDa) when newly recorded phenotypes were added to the genomic evaluation system; however, outliers had changes as high as 1 SDa, which agrees with the normal distribution theory. Although changes under genomic evaluations are more frequent than in BLUP, the observed fluctuations are small compared to the possible changes based on prediction error variance. Making selection decisions based on groups of animals with high average accuracy instead of individual animals may help to offset the impact of fluctuations in genomic evaluations.