Department of Animal Science, Department of Molecular Biology and Genetics, Faculty of Science and Technology, Aarhus University, PO Box 50, DK-8300 Tjele, Denmark.
J Dairy Sci. 2013 Mar;96(3):1820-33. doi: 10.3168/jds.2012-5528. Epub 2013 Jan 26.
Several quantitative trait loci (QTL) affecting mastitis incidence and mastitis-related traits such as somatic cell score exist in dairy cows. Previously, QTL haplotypes associated with susceptibility to Escherichia coli mastitis in Nordic Holstein-Friesian (HF) cows were identified on Bos taurus autosome 9. In the present study, we induced experimental E. coli mastitis in Danish HF cows to investigate the effect of 2 E. coli mastitis-associated QTL haplotypes on the cows' disease phenotypes and recovery in early lactation. Thirty-two cows were divided in 2 groups bearing haplotypes with either low (HL) or high (HH) susceptibility to E. coli. In addition, biopsies (liver and udder) were collected from half of the cows (n=16), resulting in a 2 × 2 factorial design, with haplotype being one factor (HL vs. HH) and biopsy being the other factor (biopsies vs. no biopsies). Each cow was inoculated with a low E. coli dose (20 to 40 cfu) in one front quarter at time 0 h. Liver biopsies were collected at -144, 12, 24, and 192 h; udder biopsies were collected at 24h and 192 h post-E. coli inoculation. The clinical parameters: feed intake, milk yield, body temperature, heart rate, respiration rate, rumen motility; and the paraclinical parameters: bacterial counts, somatic cell count (SCC), and milk amyloid A levels in milk; and white blood cell count, polymorphonuclear neutrophilic leukocyte (PMNL) count, and serum amyloid A levels in blood were recorded at different time points post-E. coli inoculation. Escherichia coli inoculation changed the clinical and paraclinical parameters in all cows except one that was not infected. Clinically, the HH group tended to have higher body temperature and heart rate than the HL group did. Paraclinically, the HL group had faster PMNL recruitment and SCC recovery than the HH group did. However, we also found interactions between the effects of haplotype and biopsy for body temperature, heart rate, and PMNL. In conclusion, when challenged with E. coli mastitis, HF cows with the specific Bos taurus autosome 9-located QTL haplotypes were associated with differences in leukocyte kinetics, with low-susceptibility cows having faster blood PMNL recruitment and SCC recovery and a tendency for a milder clinical response than the high-susceptibility cows did.
几个影响乳腺炎发病率和乳腺炎相关性状（如体细胞评分）的数量性状基因座（QTL）存在于奶牛中。先前，在北欧荷斯坦弗里生（HF）奶牛中，已经确定了与大肠杆菌乳腺炎易感性相关的 QTL 单倍型存在于牛 9 号染色体上。在本研究中，我们诱导丹麦 HF 奶牛发生实验性大肠杆菌乳腺炎，以研究 2 个与大肠杆菌乳腺炎相关的 QTL 单倍型对奶牛在泌乳早期疾病表型和恢复的影响。32 头奶牛分为两组，分别携带低（HL）和高（HH）大肠杆菌易感性的单倍型。此外，从一半的奶牛（n=16）中采集活检（肝脏和乳房），这导致了一个 2×2 因子设计，其中单倍型是一个因素（HL 与 HH），活检是另一个因素（活检与非活检）。每头奶牛在 0 小时时在前四分体中接种低剂量的大肠杆菌（20 至 40 cfu）。在-144、12、24 和 192 小时采集肝脏活检；在大肠杆菌接种后 24 小时和 192 小时采集乳房活检。临床参数：采食量、产奶量、体温、心率、呼吸频率、瘤胃蠕动；以及临床参数：细菌计数、体细胞计数（SCC）和奶中的淀粉样蛋白 A 水平；白细胞计数、多形核中性粒细胞（PMN）计数和血液中的血清淀粉样蛋白 A 水平在大肠杆菌接种后的不同时间点记录。除了一头未感染的奶牛外，大肠杆菌接种改变了所有奶牛的临床和临床参数。临床上，HH 组的体温和心率比 HL 组高。在临床方面，HL 组的 PMNL 募集和 SCC 恢复速度比 HH 组快。然而，我们还发现了单倍型和活检对体温、心率和 PMNL 的影响之间的相互作用。总之，当受到大肠杆菌乳腺炎的挑战时，具有特定牛 9 号染色体定位 QTL 单倍型的 HF 奶牛与白细胞动力学的差异相关，低易感性奶牛的血液 PMNL 募集和 SCC 恢复速度更快，临床反应较轻。
