Division of Infectious Diseases and Epidemiology, Department of Large Animal Diseases with the Clinic, Faculty of Veterinary Medicine, Warsaw University of Life Sciences, Nowoursynowska 159c, 02-776 Warsaw, Poland.
J Dairy Sci. 2012 Apr;95(4):1617-22. doi: 10.3168/jds.2011-4680.
This long-term observational cohort study was carried out to evaluate the effect of caprine arthritis-encephalitis virus (CAEV) infection on the quantitative and qualitative characteristics of milk production in dairy goats. For this purpose, a dairy herd comprising both CAEV-infected and uninfected female goats was observed for 12 consecutive years. Records on daily milk yield, somatic cell count (SCC), and contents of the major milk components (fat, protein and lactose) were collected every month. In total, 3,042 records (1,114 from CAEV-positive and 1,928 from CAEV-negative animals) from 177 female goats were used for statistical analysis. The multi-trait repeatability test-day animal model using the derivative-free multivariate analysis package with the average information-REML method was applied to eliminate the influence of factors other than CAEV infection on milk production in goats. The statistical significance of the differences between estimates for seropositive and seronegative goats was evaluated using Student's t-test. The effect of age of goats (parity) on their serological status was also estimated with the one-trait repeatability test-day model. The serological status of goats was linked to parity: the higher the parity, the greater the probability of CAEV infection. No significant differences between infected and uninfected goats with respect to daily milk yield and SCC were found. On the other hand, the milk of uninfected goats contained more total protein (3.40% vs. 3.35%), fat (3.69% vs. 3.54%), and lactose (4.30% vs. 4.25%) than the milk of infected goats. Even though these differences were highly significant, they were small when expressed numerically.
本长期观察性队列研究旨在评估山羊关节炎脑炎病毒（CAEV）感染对奶山羊产奶量的定量和定性特征的影响。为此，对一个同时包含 CAEV 感染和未感染的雌性山羊的奶牛群进行了 12 年的连续观察。每月收集每日产奶量、体细胞计数（SCC）和主要乳成分（脂肪、蛋白质和乳糖）含量的记录。总共使用了 177 只雌性山羊的 3042 条记录（1114 条来自 CAEV 阳性动物，1928 条来自 CAEV 阴性动物）进行统计分析。使用无导数多元分析软件包的多性状重复测试日动物模型，采用平均信息-REML 方法，以消除除 CAEV 感染以外的因素对山羊产奶量的影响。使用学生 t 检验评估估计值在血清阳性和血清阴性山羊之间的差异的统计学显著性。还使用单性状重复测试日模型估计了山羊年龄（胎次）对其血清学状态的影响。山羊的血清学状态与胎次有关：胎次越高，CAEV 感染的可能性越大。未发现感染和未感染山羊的日产奶量和 SCC 之间存在显著差异。另一方面，未感染山羊的奶中总蛋白（3.40%比 3.35%）、脂肪（3.69%比 3.54%）和乳糖（4.30%比 4.25%）含量均高于感染山羊的奶。尽管这些差异具有高度显著性，但在数值上很小。
