Genetic diversity and population structure of 20 North European cattle breeds

Blood samples were collected from 743 animals from 15 indigenous, 2 old imp orted, and 3 commercial North European cattle breeds. The samples were anal yzed for 11 erythrocyte antigen systems, 8 proteins, and 10 microsatellites , and used to assess inter- and intrabreed genetic variation and genetic po pulation structures. The microsatellites BoLA-DRBP1 and CSSM66 were nonneut ral markers according to the Ewens-Watterson test, suggesting some kind of selection Imposed on these loci. North European cattle breeds displayed gen erally similar levels of multilocus heterozygosity and allelic diversity. H owever, allelic diversity has been reduced in several breeds, which was exp lained by limited effective population sizes over the course of man-directe d breed development and demographic bottlenecks of indigenous breeds. A tre e showing genetic relationships between breeds was constructed from a matri x of random drift-based genetic distance estimates. The breeds were classif ied on the basis of the tree topology into four major breed groups, defined as Northern indigenous breeds, Southern breeds, Ayrshire and Friesian bree ds, and Jersey. Grouping of Nordic breeds was supported by documented breed history and geographical divisions of native breeding regions of indigenou s cattle. Divergence estimates between Icelandic cattle and indigenous bree ds suggested a separation time of more than 1,000 years between Icelandic c attle and Norwegian native breeds, a finding consistent with historical evi dence.