Van Donkersgoed J, Ribble C S, Booker C W, McCartney D, Janzen E D
Veterinary Infectious Disease Organization, Saskatoon, Saskatchewan.
Can J Vet Res. 1993 Jul;57(3):170-5.
To elucidate reasons for failure of pelvimetry to predict dystocia, we collected data from 1146 heifers and 210 cows in five beef cow herds in Saskatchewan. We assessed the reliability of pelvic area measurements, the generalizability of findings, various modifications of the technique, and the statistical association between pelvic area measurements and dystocia. The repeatability (kappa) of pelvic area measurements between and within veterinarians for the Rice and Krautmann pelvimeters were low to moderate, indicating pelvic area measurements were imprecise. The positive predictive values and sensitivities of pelvic area measurements were consistently poor across herds, years of study, breeds of heifers, times of measurement, various pelvic area cut-off points, and sires. Various modifications of the technique, including pelvic area/calf birth weight ratios, pelvic area/heifer weight ratios, and Ko's calving prediction equation were also poor on-farm tests for predicting dystocia. Although the mean pelvic area in heifers with dystocia was smaller than those without dystocia, there was a large overlap in the distribution of their measurements. Far too many heifers with a small pelvic area had no dystocia (false positives) and far too many heifers with a large pelvic area had dystocia (false negatives) for pelvimetry to be useful. We conclude there is little evidence to justify the continued use of pelvimetry as an on-farm test to reduce dystocia in beef cattle.
为了阐明骨盆测量无法预测难产的原因，我们从萨斯喀彻温省五个肉牛群的1146头小母牛和210头母牛中收集了数据。我们评估了骨盆面积测量的可靠性、研究结果的普遍性、该技术的各种改进方法，以及骨盆面积测量与难产之间的统计关联。对于赖斯和克劳特曼骨盆测量仪，兽医之间以及兽医内部骨盆面积测量的重复性（kappa值）为低到中等，表明骨盆面积测量并不精确。在各个牛群、研究年份、小母牛品种、测量时间、各种骨盆面积临界值以及公牛方面，骨盆面积测量的阳性预测值和敏感性一直都很差。该技术的各种改进方法，包括骨盆面积/犊牛出生体重比、骨盆面积/小母牛体重比以及柯氏产犊预测方程，在农场预测难产的测试中也表现不佳。虽然难产小母牛的平均骨盆面积小于未难产的小母牛，但其测量值分布有很大重叠。骨盆面积小的小母牛中没有难产的（假阳性）太多，而骨盆面积大的小母牛中有难产的（假阴性）太多，以至于骨盆测量没有用处。我们得出结论，几乎没有证据能证明继续将骨盆测量作为农场测试以减少肉牛难产是合理的。
