Dystocia is more common in Holstein-Friesian (HF) breed cows than in other dairy breeds. This is often caused by a disproportion between the birth canal of a female animal and the fetus. It is thought that the main determiners of unsuitability are the birth mass of the calf and the shape of the female pelvis. From the perspective of calving the cranial and caudal pelvic apertures are of great significance. This study focuses on pluriparous pelves of the Estonian Native Breed (EN) and the Estonian Holstein Breed (EHF). The longest measurement of the cranial pelvic aperture of an EHF cow is the conjugate diameter. The cranial pelvic aperture narrows slightly ventrally, being shaped like a trapezium with rounded angles. The longest measurement of the caudal aperture is its caudal transverse measurement. The aperture is flattened dorsoventrally. The cranial pelvic aperture of an EN cow is dorsally angular, but more oval ventrally, and is on the whole narrower and higher. By comparison with the EHF cow, the pelvic cavity of the EN cow widens caudally, and the height of the pelvic apertures contributes to ease of calving. It appears that the configuration of the pelvis of an EN cow is similar to the pelvis of the elk (Alces alces). The pelvis of the EHF cow has become unsuitable for easy calving, especially with regard to the caudal aperture.

There is no data in the literature concerning the frequency of birthing difficulties in the elk cow. This study aims to describe the pelves of elk cows and adult bulls. The measurements of an elk pelvis depend on living conditions rather than age. The dimensions of primiparous pelves are more homogeneous than those of pluriparous cows because heifers have to reach a certain weight prior to successful conception. The elk pelvis has a rather slim shape; the cavum pelvis is deep, oval lengthwise in the median plane, and narrows in the caudal direction. Primiparous and pluriparous cows were significantly different regarding the following measurements: the lengths of the diameter conjugata, the diameter transversa and the caudal transverse and the area of the aperturae pelvis. The pelvic cavity of bulls is longer and narrower in comparison with that of cows, and the areas of the pelvic apertures are smaller. A rapid delivery of the foetus is facilitated by the following factors: a uniform diameter and an appropriate angle of inclination of the bony birth canal, relative mobility of the articulatio sacroiliaca, a concave pelvic surface of the os sacrum, a slow ossification of the symphysis pelvina and the degeneration of the tuberculum pubicum dorsale. In order to differentiate between elks pelves by sex and age, the measurements of the aperturae pelvis and their ratios, the surface area of the symphysis pelvina and the pecten ossis pubis, and the position of the eminentiae iliopubicae and os interischiadicum should be recorded and analysed.