Radiographic pelvimetry for the estimation of pelvic dimensions in Merino, Dormer and S A mutton Merino ewes.

Investigations into ovine pelvic size and its relationship to repetitive rearing failure require accurate estimation of pelvic dimensions in live animals. Radiographic pelvimetry was used to estimate pelvic dimensions of 84 Merino, 21 Dormer and 20 S A Mutton Merino ewes. Transverse diameter and conjugate diameter were estimated; the area of the pelvic inlet was defined as the product of transverse and conjugate diameters. Dissected measurements obtained from all ewes after slaughter were regressed on estimated dimensions to obtain prediction equations for the correction of radiographic estimates. Prediction equations for the estimation of dissected pelvic dimensions from radiographs were accurate (r greater than or equal to 0.87), irrespective of dimension estimated or breed. Derived equations for estimation of dissected pelvic dimensions for the 3 breeds were not statistically different. It was concluded that pelvic dimensions of ewes could accurately be predicted by radiographic pelvimetry.