Data were 13734 black-and-white, Holstein-Friesian (HF) and 1/2 HF young bulls bom during 1981 - 1987, and performance tested at the central rearing stations. General characteristics of the population were given separately for two periods: 1981 - 1984 and 1985 - 1987. A large number of young bulls were single sons of several hundreds of sites, and about 30% of the young bulls were sons of sires with about 100 bulls on test HF and 1/2 HF were superior to the black-and-white strain in all traits studied, i.e. body weights at 120 and 360 days, heart girth and height at withers. Means for those traits in both periods did not differ, suggesting a lack of phenotypic progress. Coefficients of relationship and inbreeding were very low in both periods.
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