Temporal changes in genetic variation of North European cattle breeds

Temporal changes in genetic variation within and between 13 North European cattle breeds were evaluated using erythrocyte antigen systems and transfer rin protein as genetic markers. Current data on allele frequency distributi ons of markers in large commercial and smaller endangered native cattle bre eds were compared to data published during 1956 to 1975. Intrabreed genetic variation was quantified by conventional parameters (e.g. heterozygosity, average number of alleles per locus) and migration by the effective migrati on rate. The neighbour-joining dendrogram of relationships between old and present cattle populations was constructed using Nei's standard genetic dis tance, Variance effective population size was estimated from changes in all ele frequencies over time. Comparison of old and new data indicated some si gnificant changes in allele frequencies. In six of the breeds, a few low-fr equency alleles in the old data were absent in the present samples. Heteroz ygosity remained stable in most breeds. The harmonic means for variance eff ective population size ranged between 30 and 257. Current results indicate that despite marked declines in total population sizes, North European nati ve cattle breeds have retained a reasonably high genetic diversity. However , their genes contribute less than previously to genetic variation of Nordi c production breeds. Commercial breeds do not appear to have a larger effec tive population size than native breeds, The present effective population s izes imply that Nordic breeds could have lost from 1 to 11% of their hetero zygosity over a 20-40-year period.