Estimates of variances due to parent of origin effects for weights of Australian beef cattle

Abstract

Estimates of variances due to differential expression of paternally and maternally derived genes can be obtained from animal model type analyses by fitting appropriate gametic effects. This is feasible for large-scale analyses, because the inverse of the gametic relationship matrix can be set up directly from a list of pedigrees. We present a series of analyses applying such a model to large sets of records for birth, weaning, yearling and final weights of Australian Angus and Hereford cattle. On one hand, results show that maternal genetic effects on these traits are largely confounded with maternal parent of origin effects, so that it is difficult to reliably separate the respective variance components. On the other hand, paternal parent of origin effects tend to act similarly to sire x herd effects so that estimates of their variance are inflated by any effects not modelled and contributing to such apparent interaction. Fitting an animal model with both parent of offspring effects, maternal genetic and permanent environmental effects as well as sire x herd and maternal grand-sire x herd of origin of dam interactions as additional random effects yielded estimates of the variance due to paternal parent of origin effects of 5-7% of the phenotypic variation for birth and weaning weights and of 0-1% for yearling and final weights. Corresponding estimates for maternal parent of origin effects were 0-11% for birth and weaning weights and 7-8% for yearling and final weights, while sire and maternal grand-sire interaction effects explained from 0 to 4% of the phenotypic variance.