Appuhamy J A D R N, Cassell B G, Dechow C D, Cole J B
Department of Dairy Science, Virginia Polytechnic Institute and State University, Blacksburg 24061, USA.
J Dairy Sci. 2007 Sep;90(9):4424-34. doi: 10.3168/jds.2007-0077.
The objective of this study was to investigate the phenotypic relationship between common health disorders in dairy cows and lactation persistency, uncorrelated with 305-d yield. The relationships with peak yield and days in milk (DIM) at peak were also studied. Daily milk weights and treatment incidence records of 991 Holstein lactations from experimental dairy herds at Virginia Tech and Pennsylvania State University were used. Persistency was calculated as a function of daily yield deviations from standard lactation curves, developed separately for first (FL) and later lactations (LL), and deviations of DIM around reference dates: 128 for FL and 125 for LL. Days in milk at peak and peak yield were computed for each lactation by using Wood's function. The disease traits studied were mastitis (MAST) only during the first 100 d (MAST1), only after 100 DIM (MAST2), both before and after 100 DIM (MAST12), and at any stage of lactation (MAST1/2), as well as metritis, displaced abomasums, lameness, and metabolic diseases. Each disease was defined as a binary trait, distinguishing between lactations with at least one incidence (1) and lactations with no incidences (0). The relationships of diseases to persistency, DIM at peak, and peak yield were investigated separately for FL and LL for all disease traits except MAST12, which was investigated across parities. The relationships of persistency to probability of the diseases in the same lactation and in the next lactation were examined using odds ratios from a logistic regression model. Metritis and displaced abomasums in FL and LL were associated with significantly higher persistencies. Metabolic diseases and MAST1 in LL were significantly related to higher persistencies. The relationships of MAST2 in both FL and LL, and MAST12 across parities were significant but negative. Cows affected by MAST tended to have less persistent lactations. Most of the diseases had a significant impact on DIM at peak in LL. In LL, metritis, metabolic diseases, and displaced abomasums tended to significantly delay DIM at peak. Mastitis only after 100 DIM was associated with significantly earlier DIM at peak in LL. Increasing persistency was associated with low MAST2 and MAST1/2 in primiparous cows. None of the diseases studied was significantly related to persistency of the previous lactation.
本研究的目的是调查奶牛常见健康障碍与泌乳持续性之间的表型关系，且该关系与305天产奶量无关。同时还研究了与峰值产奶量以及峰值时的泌乳天数（DIM）之间的关系。使用了来自弗吉尼亚理工大学和宾夕法尼亚州立大学实验奶牛场的991头荷斯坦奶牛泌乳期的每日产奶量和疾病发生记录。持续性通过偏离标准泌乳曲线的日产量来计算，标准泌乳曲线分别针对头胎（FL）和经产（LL）泌乳期制定，以及围绕参考日期的DIM偏差：头胎为128天，经产为125天。每个泌乳期的峰值泌乳天数和峰值产奶量通过伍德函数计算得出。所研究的疾病特征包括仅在泌乳前100天内的乳腺炎（MAST）（MAST1）、仅在100天泌乳期后出现的乳腺炎（MAST2）、100天泌乳期前后均出现的乳腺炎（MAST12）以及泌乳期任何阶段的乳腺炎（MAST1/2），还有子宫炎、真胃移位、跛行和代谢疾病。每种疾病都被定义为二元性状，区分至少有一次发病的泌乳期（1）和无发病的泌乳期（0）。除MAST12在不同胎次间进行研究外，对于所有疾病特征，分别对头胎和经产的疾病与持续性、峰值时的DIM以及峰值产奶量之间的关系进行了研究。使用逻辑回归模型的优势比来检验同一泌乳期和下一泌乳期疾病的持续性与发病概率之间的关系。头胎和经产的子宫炎和真胃移位与显著更高的持续性相关。经产的代谢疾病和MAST1与更高的持续性显著相关。头胎和经产的MAST2以及不同胎次间的MAST12之间的关系显著但为负相关。受乳腺炎影响的奶牛泌乳持续性往往较低。大多数疾病对经产的峰值时的DIM有显著影响。在经产中，子宫炎、代谢疾病和真胃移位往往会显著延迟峰值时的DIM。仅在100天泌乳期后出现的乳腺炎与经产中显著更早的峰值时的DIM相关。初产奶牛泌乳持续性增加与低MAST2和MAST1/2相关。所研究的疾病均与上一泌乳期的持续性无显著关系。
