On the basis of a group of progeny derived from cows characterised by record milk yields, long-term inbreeding experiments were carried out. One F1 bull was obtained which was inbred in 25% and which, following a successfully completed progeny test, was further used for mating. Ultimately, twelve progeny groups comprising over 350 primiparas were analysed. Inbred groups were compared with 488 age mates. The objective of the research project was to develop progeny characterised by a distinctly higher homozygosity, which, as it was hoped, would allow replicating record milk yields of their progenitors. Progeny derived from matings of father with daughter did not guarantee highest milk yields. The group with the lowest degree of inbreeding (matings grandfather with granddaughter) gave the best results.

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