体细胞计数(SCC)是牛乳房健康状况的重要指标。然而,用于区分健康奶牛与亚临床乳腺炎奶牛的确切临界值仍存在争议。这里,我们从两个不同奶牛场的个体奶牛中收集了复合乳(来自四个乳房季度的乳)和外周血样本,并使用16SrRNA基因测序结合RNA-seq来探索具有三种不同SCC水平的奶牛的乳微生物组成和转录组的差异(LSCC:<100,000个细胞/mL,MSCC:100,000-200,000个细胞/mL,HSCC:>200,000个细胞/mL)。结果表明,MSCC组中来自奶牛的样品的乳微生物谱和基因表达谱确实相对容易地与LSCC组中的奶牛区分开。判别分析还发现了属水平的一些差异丰富的微生物群,例如双歧杆菌和落叶松科_AC2044_组,其在来自SCC低于100,000个细胞/mL的奶牛的牛奶样品中更丰富。至于转录组分析,发现79个差异表达基因(DEGs)在两个位点具有相同的调控方向,和功能分析还表明,参与炎症反应的生物过程在MSCC和HSCC奶牛中更活跃。总的来说,这些结果显示了MSCC和HSCC奶牛的乳菌群和基因表达谱之间的相似性,这提供了进一步的证据,100,000个细胞/ml比200,000个细胞/mL在奶牛水平的乳房内感染检测是更最佳的截止值。
Somatic cell count (SCC) is an important indicator of the health state of bovine udders. However, the exact cut-off value used for differentiating the cows with healthy quarters from the cows with subclinical mastitis remains controversial. Here, we collected composite milk (milk from four udder quarters) and peripheral blood samples from individual cows in two different dairy farms and used 16S rRNA gene sequencing combined with RNA-seq to explore the differences in the milk microbial composition and transcriptome of cows with three different SCC levels (LSCC: <100,000 cells/mL, MSCC: 100,000−200,000 cells/mL, HSCC: >200,000 cells/mL). Results showed that the milk microbial profiles and gene expression profiles of samples derived from cows in the MSCC group were indeed relatively easily discriminated from those from cows in the LSCC group. Discriminative analysis also uncovered some differentially abundant microbiota at the genus level, such as Bifidobacterium and Lachnospiraceae_AC2044_group, which were more abundant in milk samples from cows with SCC below 100,000 cells/mL. As for the transcriptome profiling, 79 differentially expressed genes (DEGs) were found to have the same direction of regulation in two sites, and functional analyses also showed that biological processes involved in inflammatory responses were more active in MSCC and HSCC cows. Overall, these results showed a similarity between the milk microbiota and gene expression profiles of MSCC and HSCC cows, which presented further evidence that 100,000 cells/ml is a more optimal cut-off value than 200,000 cells/mL for intramammary infection detection at the cow level.