Zoche-Golob V, Heuwieser W, Krömker V
Department of Bioprocess Engineering-Microbiology Faculty 2, University of Applied Science and Arts, Heisterbergallee 12, 30453 Hannover, Germany; Clinic of Animal Reproduction, Department of Veterinary Medicine, Freie Universität Berlin, Königsweg 65, 14163 Berlin, Germany.
Clinic of Animal Reproduction, Department of Veterinary Medicine, Freie Universität Berlin, Königsweg 65, 14163 Berlin, Germany.
Prev Vet Med. 2015 Sep 1;121(1-2):64-73. doi: 10.1016/j.prevetmed.2015.06.018. Epub 2015 Jun 25.
The objective of the present study was to investigate the association between the milk fat-protein ratio and the incidence rate of clinical mastitis including repeated cases of clinical mastitis to determine the usefulness of this association to monitor metabolic disorders as risk factors for udder health. Herd records from 10 dairy herds of Holstein cows in Saxony, Germany, from September 2005-2011 (36,827 lactations of 17,657 cows) were used for statistical analysis. A mixed Poisson regression model with the weekly incidence rate of clinical mastitis as outcome variable was fitted. The model included repeated events of the outcome, time-varying covariates and multilevel clustering. Because the recording of clinical mastitis might have been imperfect, a probabilistic bias analysis was conducted to assess the impact of the misclassification of clinical mastitis on the conventional results. The lactational incidence of clinical mastitis was 38.2%. In 36.2% and 34.9% of the lactations, there was at least one dairy herd test day with a fat-protein ratio of <1.0 or >1.5, respectively. Misclassification of clinical mastitis was assumed to have resulted in bias towards the null. A clinical mastitis case increased the incidence rate of following cases of the same cow. Fat-protein ratios of <1.0 and >1.5 were associated with higher incidence rates of clinical mastitis depending on week in milk. The effect of a fat-protein ratio >1.5 on the incidence rate of clinical mastitis increased considerably over the course of lactation, whereas the effect of a fat-protein ratio <1.0 decreased. Fat-protein ratios <1.0 or >1.5 on the precedent test days of all cows irrespective of their time in milk seemed to be better predictors for clinical mastitis than the first test day results per lactation.
本研究的目的是调查乳脂肪 - 蛋白质比率与临床乳腺炎发病率（包括临床乳腺炎的复发病例）之间的关联，以确定这种关联对于监测作为乳腺健康风险因素的代谢紊乱的有用性。使用了德国萨克森州10个荷斯坦奶牛场2005年9月至2011年的牛群记录（17,657头奶牛的36,827次泌乳）进行统计分析。拟合了以临床乳腺炎每周发病率为结果变量的混合泊松回归模型。该模型包括结果的重复事件、随时间变化的协变量和多水平聚类。由于临床乳腺炎的记录可能不完美，因此进行了概率偏差分析，以评估临床乳腺炎误分类对传统结果的影响。临床乳腺炎的泌乳发病率为38.2%。在36.2%和34.9%的泌乳期，分别至少有一个奶牛场测试日的脂肪 - 蛋白质比率<1.0或>1.5。假定临床乳腺炎的误分类导致偏向无效值。临床乳腺炎病例会增加同一头牛后续病例的发病率。根据泌乳周数，脂肪 - 蛋白质比率<1.0和>1.5与临床乳腺炎的较高发病率相关。脂肪 - 蛋白质比率>1.5对临床乳腺炎发病率的影响在泌乳过程中大幅增加，而脂肪 - 蛋白质比率<1.0的影响则下降。无论奶牛处于泌乳的哪个阶段，所有奶牛前一个测试日的脂肪 - 蛋白质比率<1.0或>1.5似乎比每次泌乳的第一个测试日结果更能预测临床乳腺炎。
