A beautiful cow is a good cow. Dutch scientists and commercial breeders on cattle breeding, 1900-1950 In the agricultural journal De Nieuwe Veldbode of 1941 Dutch scientists, agricultural engineers, commercial cattle breeders and herd-book officials engaged in a prolonged debate about cattle breeding methods. Geneticist Arend Hagedoorn started the debate by accusing commercial breeders of deceiving their buyers. In his view, breeders were merely interested in producing beautiful show bulls that could be sold for high prices, and they ignored the animals’ hereditary potential for milk production. Rational breeding, he argued, required progeny testing: only the production of his daughters should decide on a bull’s merits. Commercial breeders denied the charge. They did indeed select for conformation, not however for aesthetic reasons, but to safeguard the health and durability of the breed. In their view, selecting for production was not feasible in practice and would, moreover, lead to the degeneration of the breed. In this article I explore the backgrounds of this debate by investigating the different views of scientists and practical breeders on theory and practice of cattle breeding in the first half of the century. I shall show that to understand the different viewpoints, the practical realities of dairy farming under Dutch circumstances, commercial considerations and normative ideas on good farming have to be taken into account.