Pritchett L C, Gay C C, Hancock D D, Besser T E
College of Veterinary Medicine, Washington State University, Pullman 99164-6610.
J Dairy Sci. 1994 Jun;77(6):1761-7. doi: 10.3168/jds.S0022-0302(94)77117-4.
Hydrometer measurement in globulin and IgG1 concentration measured by the radial immunodiffusion technique were compared for 915 samples of first milking colostrum from Holstein cows. Least squares analysis of the relationship between hydrometer measurement and IgG1 concentration was improved by log transformation of IgG1 concentration and resulted in a significant linear relationship between hydrometer measurement and log10 IgG1 concentration; r2 = .469. At 50 mg of globulin/ml of colostrum, the recommended hydrometer cutoff point for colostrum selection, the sensitivity of the hydrometer as a test of IgG1 concentration in Holstein colostrum was 26%, and the negative predictive value was 67%. The negative predictive value and sensitivity of the hydrometer as a test of IgG1 in Holstein colostrum was improved, and the cost of misclassification of colostrum was minimized, when the cutoff point for colostrum selection was increased above the recommended 50 mg/ml.
对915份荷斯坦奶牛初乳样本，比较了用比重计测量和用放射免疫扩散技术测量球蛋白及IgG1浓度的结果。通过对IgG1浓度进行对数转换，改善了比重计测量值与IgG1浓度之间关系的最小二乘法分析，得到比重计测量值与log10 IgG1浓度之间显著的线性关系；r2 = 0.469。在初乳球蛋白浓度为50 mg/ml时（这是初乳选择推荐的比重计临界值），比重计作为检测荷斯坦初乳中IgG1浓度的检测方法，其灵敏度为26%，阴性预测值为67%。当将初乳选择的临界值提高到高于推荐的50 mg/ml时，比重计作为检测荷斯坦初乳中IgG1的阴性预测值和灵敏度提高，初乳误分类的成本最小化。
