Abstract. Suckling behaviour of nine beef cow-calf-pairs (Hereford and Charolais) and five dairy cow-calf-pair's (Polish Holstein-Friesian) was video-recorded from day one pp to day 70 (beef) or 82 (dairy) post partum (pp) regularly. Cows were only suckled during that time and milk yield could not be recorded. Bout was defined as all activities of the calf from the first contact between the mouth of the calf at a specific teat and the last contact at this teat, i.e., as a small sub-unit of a meal. Number of suckled teats, uniformity of relative shares of suckled teats, number of bouts, average bout and relative number of bout-teat-repetitions described the course of ontogeny of suckling behaviour. The first model included the effects breed, cow (breed), and day pp as regression. The analysis revealed the following: (i) number of teats, uniformity of relative shares between suckled teats, and number of bouts increased with increasing day pp. (ii) Average bout, relative number of bout-teat repetitions and mealbout- relationship decreased with increasing day pp. (iii) The same developments could be observed in both breeds, however, significantly slower in the dairy breed. The second model included the effects breed, cow (breed) and average bout as regression, representing milk yield. Breed changed from a very powerful into an almost negligible effect in that second analysis. The implications of the results for a wider group of mammalian species are discussed.