The impact of heterogeneous residual variance across years on estimated breeding values for fly strike in Australian Merino sheep

Abstract

<p>The accurate genetic evaluation of livestock requires accounting for possible heterogeneity in data to accommodate differences across groups of animals in the levels of residual variance that might exist between years, flocks and locations. Genetic heterogeneity may also exist due to the environments creating different expressions of traits (Mulder et al. 2007). Ignoring the heterogeneity of variances may lead to incorrect ranking and selection of sires and dams, loss of expected genetic gain, and decreased breeding program efficiency (Henderson, 1975). This study was conducted to examine the presence of heterogeneous residual variance in breech strike records as well as the impact of pre-analysis standardisation of data on reducing heterogeneity of variance and accuracy of prediction of genomic estimated breeding values (GEBVs) in the Connemara Merino ram breeding flock.</p>