NORDIC DAIRY-CATTLE COMPARISON FOR MILK-PRODUCTION BY USING A MIXED LINEAR-MODEL APPROACH

The exchange of genetic material between the dairy cattle populations in the Nordic countries is well established. Initially the following Nordic dairy cattle populations were used to perform a comparison of their genetic levels for milk production: the Norwegian Cattle (NRF), the Swedish Red and White Cattle (SRB), and the Finnish Ayrshire Cattle (FAY). A linear model, including genetic base of sire proofs and genetic group made up by breed composition and date of birth of sire as fixed effects and sire as a random effect, was applied to standardize and deregress official sire proofs. The result was expressed as Nordic transmitting ability in kg of fat- and protein-corrected milk (FPM). The overall average of Nordic proofs of sires used in the NRF population was, respectively, 72 and 151 kg FPM higher than those of sires proven in the SRB and FAY populations. A genetic comparison of the breeds gave the same general result. The annual genetic trends were 25.5, 16.7 and 30.4 kg FPM in the NRF, SRB and FAY populations. Actually, the highest selection differentials were measured for bull sires in the FAY population. Sons of foreign bull sires had an overall negative impact in the NRF population, but a positive impact in both the SRB and FAY populations. © 1990.