JOINT GENETIC EVALUATION OF BLACK-AND-WHITE DAIRY BULLS IN THE NORDIC COUNTRIES FOR DAIRY PRODUCTION TRAITS

Genetic ties between the Black-and-White dairy bull populations of Denmark, Finland and Sweden were investigated using pedigree records. Although direct ties were weak, substantial linkage existed via common exporting countries, namely Canada, Germany, the Netherlands and the USA. A joint evaluation of bulls progeny-tested in these three Nordic countries was feasible in the presence of data from the four exporting countries. National proofs of more than 35 000 bulls from these countries were then analyzed with a linear model to rank bulls across country for milk, fat and protein yields. Results from the international evaluation were consistent with results from individual national evaluations. National proofs of bulls whose semen had been imported into the Nordic countries were found biased upwards by an average 4-5%, resulting in a substantial over-estimation of the international proofs of foreign bulls. Excluding these records from the analysis did not affect the data connectedness. Joint Nordic evaluations should be calculated using data only from the country where bulls receive their first official proof.