Rola J G, Larska M, Grzeszuk M, Rola J
Department of Hygiene of Food of Animal Origin, National Veterinary Research Institute, Al. Partyzantow 57, 24-100 Pulawy, Poland.
Department of Virology, National Veterinary Research Institute, Al. Partyzantow 57, 24-100 Pulawy, Poland.
J Dairy Sci. 2015 Feb;98(2):781-9. doi: 10.3168/jds.2014-8781. Epub 2014 Dec 12.
Bovine herpesvirus 1 (BoHV1) is one of the most important pathogens of cattle; however, its effect on somatic cell count and milk components is not completely understood. The aim of the current study was to examine the effect of BoHV1 infection on quality of bovine bulk tank milk (BTM). A total of 1,790 individual blood samples collected at 28 dairy farms were used to determine the BoHV1 infection status of the herds with ELISA tests. The quality parameters of milk were evaluated by instrumental methods with BTM samples collected at monthly intervals from May 2011 to May 2012. The statistical analysis was performed to study the associations between BoHV1 herd status, quality of BTM, and herd-specific parameters. The risk factors influencing bulk milk somatic cell count (BMSCC) were estimated using the multivariable mixed-effects maximum likelihood regression model. The true prevalences of BoHV1 infection at the animal and herd levels were 49.3 and 64.6%, respectively. The average BMSCC differed significantly between the herds grouped accordingly to their BoHV1 infection status. Interestingly, the highest BMSCC was observed in the vaccinated herds (240.3×10(3) cells/mL). Additionally, the BoHV1 herd status had a significant effect on the fat content of BTM. The largest herds that were investigated had a BoHV1 seroprevalence over 30%. The herd status was considerably influenced by the numbers of cows in the herds. Besides, no significant differences in total bacterial count or protein content in milk from BoHV1-infected und uninfected herds were observed. An increase in BMSCC was observed during summer compared with the winter months regardless of the BoHV1 status of the herds. In the final multivariable regression model, the main risk factors associated with BMSCC were BoHV1 herd status, the percentage of BoHV1 infected animals in a herd, the number of cows in a herd, and the season. Our study suggests that BoHV1 infection may influence BMSCC levels, which are key parameters of BTM quality and a reference for subclinical mastitis in a herd. In conclusion, BoHV1 infection may cause economic losses by decrease both of quantity and quality of milk.
牛疱疹病毒1型（BoHV1）是牛最重要的病原体之一；然而，其对体细胞计数和牛奶成分的影响尚未完全明确。本研究的目的是检测BoHV1感染对牛群混合奶（BTM）质量的影响。通过酶联免疫吸附测定（ELISA）试验，使用从28个奶牛场采集的1790份个体血样来确定牛群的BoHV1感染状况。从2011年5月至2012年5月，每月采集BTM样本，采用仪器方法评估牛奶的质量参数。进行统计分析以研究BoHV1牛群感染状况、BTM质量和牛群特定参数之间的关联。使用多变量混合效应最大似然回归模型估计影响混合奶体细胞计数（BMSCC）的风险因素。动物和牛群水平上BoHV1感染的实际患病率分别为49.3%和64.6%。根据BoHV1感染状况分组的牛群中，平均BMSCC存在显著差异。有趣的是，在接种疫苗的牛群中观察到最高的BMSCC（240.3×10³个细胞/毫升）。此外，BoHV1牛群感染状况对BTM的脂肪含量有显著影响。所调查的最大牛群的BoHV1血清阳性率超过30%。牛群感染状况受牛群中奶牛数量的显著影响。此外，在BoHV1感染和未感染的牛群的牛奶中，总细菌计数或蛋白质含量未观察到显著差异。无论牛群的BoHV1感染状况如何，与冬季相比，夏季观察到BMSCC增加。在最终的多变量回归模型中，与BMSCC相关的主要风险因素是BoHV1牛群感染状况、牛群中BoHV1感染动物的百分比、牛群中奶牛的数量和季节。我们的研究表明，BoHV1感染可能影响BMSCC水平，BMSCC是BTM质量的关键参数和牛群亚临床乳腺炎的参考指标。总之，BoHV1感染可能通过降低牛奶的数量和质量而导致经济损失。
