The usefulness of pelvic area measurements as an on-farm test for predicting calving difficulty in beef heifers.

Data collected from 197 replacement heifers in four beef cow herds in Saskatchewan were analyzed to determine the usefulness of pelvic area measurements as an on-farm test for predicting calving difficulty.The prevalence of calving difficulty in these herds ranged from 15-34%. Pelvic area measurements prior to the breeding season and at the time of pregnancy examination had poor positive predictive values and sensitivities in each herd. These findings were consistent whether the measurement used as a cut-off point to distinguish between a large and a small pelvic area was the lower 25th percentile, the mean, or the common standard. Standard pelvic area and calf birth weight ratios were not useful in estimating deliverable calf birth weight.Based on these results, pelvic area measurements prior to the breeding season and at the time of pregnancy examination are poor tests for predicting calving difficulty.