A genetic model involving fetal effects on traits of the dam

The genetic fetal effects model shows that the usual sire effect is composed of one-half the direct additive genetic value and one-fourth of the fetal additive genetic value of the sire. The usual sire component of variance is actually the variance of that function. Genetic covariances between records of relatives influenced by fetuses of related sires can easily be written. If the magnitude of fetal sire effects is such that nonrandom use of fetal sires on daughters of sires being evaluated on daughter performance results in bias, the bias can be eliminated (Henderson 1975) by considering the fetal sire effects to be fixed effects. Some reduction in prediction error variance is likely by including fetal sire in the sire evaluation model.