Faculty of Veterinary Medicine, University of Calgary, Calgary, AB, Canada T2N 4N1.
Faculty of Veterinary Medicine, University of Calgary, Calgary, AB, Canada T2N 4N1.
J Dairy Sci. 2024 Jan;107(1):530-539. doi: 10.3168/jds.2023-23695. Epub 2023 Sep 13.
The objective was to evaluate the effects of bovine leukemia virus (BLV) infection, as determined by BLV seropositivity and proviral load, on 305-d milk, fat, and protein production of dairy cows. A cross-sectional study was conducted among 1,712 cows from 9 dairy herds in Alberta, Canada. The BLV status was assessed using an antibody ELISA, whereas BLV proviral load in BLV-seropositive cattle was determined with quantitative PCR. Dairy Herd Improvement 305-d milk, fat, and protein production data were obtained for all enrolled cattle. Differences in these milk end points were assessed in 2 ways: first, by categorizing cows based on BLV serostatus (i.e., BLV positive or negative), and second, by categorizing based on BLV proviral load (i.e., BLV negative, low proviral load [LPL] BLV positive, and high proviral load [HPL] BLV positive). A mixed-effect multivariable linear regression model was used to assess differences in milk parameters. We found that BLV positivity, adjusted for parity and natural log-transformed somatic cell count (SCC), was not associated with reduction in 305-d milk, fat, or protein production. However, significant reductions in 305-d milk, fat, and protein yield occurred in HPL cows, but not in LPL cows, compared with BLV-negative cows, when adjusted for parity number and natural log-transformed SCC. In summary, BLV proviral load may predict effects of BLV infection on milk, fat, and protein production.
本研究旨在评估牛白血病病毒（BLV）感染的影响，通过 BLV 血清阳性和前病毒载量来确定，对奶牛 305 天产奶量、乳脂率和乳蛋白率的影响。该研究采用横断面研究方法，在加拿大阿尔伯塔省的 9 个奶牛场中，选择了 1712 头奶牛进行研究。BLV 状态通过抗体酶联免疫吸附试验（ELISA）进行评估，而 BLV 血清阳性牛的 BLV 前病毒载量则通过定量 PCR 确定。所有入组奶牛的奶牛场改良协会（DHI）305 天产奶量、乳脂率和乳蛋白率数据均已获得。通过两种方式评估这些牛奶指标的差异：首先，根据 BLV 血清学状态（即 BLV 阳性或阴性）对奶牛进行分类，其次，根据 BLV 前病毒载量（即 BLV 阴性、低前病毒载量 [LPL] BLV 阳性和高前病毒载量 [HPL] BLV 阳性）进行分类。采用混合效应多变量线性回归模型评估牛奶参数的差异。我们发现，调整了胎次和自然对数转换的体细胞计数（SCC）后，BLV 阳性与 305 天产奶量、乳脂率或乳蛋白率的降低无关。然而，与 BLV 阴性奶牛相比，HPL 奶牛的 305 天产奶量、乳脂率和乳蛋白率显著降低，但 LPL 奶牛没有。调整胎次和自然对数转换的 SCC 后，结果相似。综上所述，BLV 前病毒载量可能预测 BLV 感染对牛奶、乳脂率和乳蛋白率的影响。
