ANIMAL-MODEL ESTIMATION OF NONADDITIVE GENETIC-PARAMETERS IN DAIRY-CATTLE, AND THEIR EFFECT ON HERITABILITY ESTIMATION AND BREEDING VALUE PREDICTION

First lactation production records of pedigree Holstein-Friesian cows in the UK were analysed by an animal model, in order to estimate effec ts of heterosis and recombination loss between North American Holstein and European Friesian cattle and the influence of these effects on br eeding value prediction. Coefficients of heterosis and recombination l oss were fitted in the animal model as covariables and unknown parents were assigned to a varying number of genetic groups. The estimates of heterosis effects were 104 kg, 4.3 kg and 2.9 kg for milk, fat and pr otein respectively, while the corresponding coefficients for recombina tion loss were -135 kg, -2.6 kg and -3.7 kg respectively. Neither the sire component of variance nor the heritability estimates were appreci ably affected by the inclusion of heterosis and recombination loss in the model. Including both these effects in the breeding value estimati on increased the predicted sire proof for fat plus protein of a typica l F1 Holstein X Friesian sire by 3 kg.