Ferguson J D, Galligan D T, Blanchard T, Reeves M
Center for Animal Health and Productivity, University of Pennsylvania, School of Veterinary Medicine, New Bolton Center, Kennett Square 19348.
J Dairy Sci. 1993 Dec;76(12):3742-6. doi: 10.3168/jds.S0022-0302(93)77716-4.
Total of 627 AI in 332 Holstein cows in nine herds were used to examine the relationship between serum urea N and conception rate. Cows were assigned randomly to one of three isocaloric diets varying in protein degradability and content. The AI occurred from 50 to 150 DIM. Mean serum urea N for each cow from 50 to 150 DIM was used to examine conception rate and serum urea N. The clinical interpretation of serum urea N on conception rate is evaluated using Bayes theorem from two approaches (dichotomization vs. continuous). Test information resulting from dichotomization of serum urea N into high and low categories (maximizing the average of test sensitivity and specificity) is compared with likelihood ratio approaches allowing a continuous measure. Likelihood ratio test indicates that conception rate decreases with serum urea N of > 14.9 mg/dl, but dichotomized test suggests that the decrease does not occur until serum urea N is > 20 mg/dl.
对9个牛群中332头荷斯坦奶牛的627次人工授精数据进行分析，以研究血清尿素氮与受孕率之间的关系。奶牛被随机分配到三种等热量但蛋白质降解率和含量不同的日粮中。人工授精在产后50至150天进行。计算每头奶牛在产后50至150天的平均血清尿素氮水平，并用于分析受孕率和血清尿素氮之间的关系。采用贝叶斯定理从两种方法（二分法与连续法）评估血清尿素氮对受孕率的临床解释。将血清尿素氮分为高、低两类（使检测敏感性和特异性的平均值最大化）所得到的检测信息与允许连续测量的似然比方法进行比较。似然比检验表明，当血清尿素氮>14.9mg/dl时，受孕率下降，但二分法检验表明，直到血清尿素氮>20mg/dl时才会出现下降。
