The body shape of an animal population determines ranges of biological functionality and productive use. In sheep, meat productivity is closely related with the body size of the animal. Some sheep breeds are used in terminal crossbreeding to give the lamb favorable dimensional characteristics, but it is necessary to go deeper on the study of the relationships between morphostructure and productive aptitude of these breeds, since discrepancies could be due to the environmental effects or the degree of differentiation between the original pool of different breeds and the local populations. The study aimed to evaluate the morphostructural characters in four sheep breeds in Chile and discuss their relationship with the productive functionality of the body architecture. Two hundred and seventy-eight sheep belonging to Texel, Dorset, Coopworth and Suffolk Down breeds were used. Eleven body measurements (heart girth circumference, rump width, rump length, width of the cranium, length of the cranium, dorsal-sternal diameter, bicostal diameter, longitudinal diameter, cannon bone circumference, height at rump and height at withers) were taken. Nine zoometric indices (body index, cephalic index, thorax index, thorax depth index, pelvic index, longitudinal pelvic index, transverse pelvic index), metacarpal thorax index and metacarpal costal index) were composed from the individual measurements. The most important morphostructural relationships that contribute to explain the variability of the format of the four breeds of sheep studied were expressed by the metacarpal- thoracic index, the metacarpal-costal index, the thorax index and the bicostal index. Moreover, the breeds showed a high dispersion; the zoometric indices only partially explained the variability of the body format, expressing high format heterogeneity in influential varia- bles as the metacarpal-thoracic index, the metacarpal-costal index and the body index. This could be because these racial populations are subjected to processes of differentiation within each breed.
