The impact of introgressed genes from Red-Holstein, Swedish Bed and White, and Finnish Ayrshire sires on daily milk-, fat-, and protein yield and on somatic cell count in German Angler cows was investigated. Univariate sire models were used for each trait and each laktation number (1-3) separately. Regression coefficients were incorporated in these models in order to estimate additive breed-effects and six possible heterosis effects. Additive breed effects were significant for milk in all three parities and protein yield in the first two parities (p <.05), but not for fat yield. For somatic cell count there was a significant effect only in the first lactation. No significant heterosis was found for any trait investigated. The estimates for additive breed differences (relative to pure Angler cows) where in a range between 2.3 kg and 4.0 kg, 20 g and 90 g, and 30 g and 110 g for milk-, fat-, and protein yield respectively, with the highest estimates for Swedish Red and White.