Maffra Veterinary Centre, 10 Johnson Street, Maffra, Victoria 3860, Australia.
J Dairy Sci. 2010 Oct;93(10):4582-91. doi: 10.3168/jds.2009-2956.
Cows (n=2,053) from 6 seasonally calving dairy herds were enrolled in a trial to compare the efficacy of 2 dry cow treatments. Cows received either a combination dry cow therapy of 600 mg of cloxacillin (CL) followed by an internal teat sealant (ITS) containing 2.6 g of bismuth subnitrate in all 4 quarters immediately following their final milking for the season, or only an intramammary infusion of 600 mg of CL. All cases of clinical mastitis were recorded and cultured during the first 150 d of lactation in each herd, and cow somatic cell count (SCC) was measured between 7 and 50 d postcalving. A large difference was found between treatment groups in the rate at which cows were diagnosed with clinical mastitis over the first 21 d of lactation, after which time the rate at which cows were diagnosed with clinical mastitis was similar between treatment groups. Analysis of the relative proportions of cows with clinical mastitis was performed at both the gland and cow levels. The relative risk (RR) of clinical mastitis diagnosed within 21, 30, and 100 d of calving in a gland treated with the ITS-CL combination was, respectively, 0.30 [95% confidence interval (CI)=0.21-0.44], 0.39 (0.28-0.53), and 0.58 (0.46-0.75) that of the CL group. An interaction between treatment and previous SCC was found when clinical mastitis was analyzed at the cow level. In a subset of cows that had low SCC in their previous lactation, the RR of mastitis in cows with the ITS-CL combination within 21, 30, and 100 d of calving was, respectively, 0.54 (95% CI=0.33-0.87), 0.57 (0.37-0.88), and 0.69 (0.50-0.99) that of cows that received only CL at drying off. In the subset of cows that had at least 1 high SCC in the previous lactation, the RR of mastitis in the ITS-CL combination group within 21, 30, and 100 d of calving was, respectively, 0.26 (95% CI=0.16-0.44), 0.37 (0.24-0.57), and 0.72 (0.55-0.96) that of the CL-only group. The ITS-CL combination of dry cow treatments was associated with a reduction in subclinical mastitis [SCC ≥250,000 cells/mL; RR=0.80 (95% CI=0.65-0.98)] when compared with treatment with CL alone. The use of an ITS in combination with CL dry cow treatment was associated with significantly lower clinical and subclinical mastitis in the following lactation, with a greater difference found in cows that had a history of subclinical mastitis in the previous lactation.
从 6 个季节性产奶牛群中招募了 2053 头奶牛，进行了一项比较两种干奶牛治疗效果的试验。奶牛在本季最后一次挤奶后立即接受 600mg 氯唑西林（CL）的联合干奶牛治疗，随后在所有 4 个乳区中使用含有 2.6g 亚硝酸铋的内部乳头密封剂（ITS），或者仅接受 600mg CL 的乳房内输液。在每个牛群的泌乳期的前 150d 中记录和培养了所有临床乳腺炎病例，并在产后 7-50d 之间测量了奶牛的体细胞计数（SCC）。在泌乳期的前 21d 内，接受 ITS-CL 联合治疗的奶牛被诊断为临床乳腺炎的比率与接受 CL 治疗的奶牛之间存在很大差异，此后，两组奶牛被诊断为临床乳腺炎的比率相似。在乳房和奶牛两个水平上对患有临床乳腺炎的奶牛比例进行了分析。在接受 ITS-CL 联合治疗的乳房中，在产后 21、30 和 100d 内被诊断为临床乳腺炎的奶牛的相对风险（RR）分别为 0.30（95%置信区间[CI]：0.21-0.44）、0.39（0.28-0.53）和 0.58（0.46-0.75），而 CL 组为 0.30（95%CI：0.21-0.44）、0.39（0.28-0.53）和 0.58（0.46-0.75）。当在奶牛水平上分析临床乳腺炎时，发现治疗与之前的 SCC 之间存在交互作用。在之前泌乳期 SCC 较低的奶牛亚组中，在产后 21、30 和 100d 内接受 ITS-CL 联合治疗的奶牛发生乳腺炎的 RR 分别为 0.54（95%CI：0.33-0.87）、0.57（0.37-0.88）和 0.69（0.50-0.99），而接受干奶时仅接受 CL 治疗的奶牛为 0.54（95%CI：0.33-0.87）、0.57（0.37-0.88）和 0.69（0.50-0.99）。在之前泌乳期至少有一次 SCC 较高的奶牛亚组中，在产后 21、30 和 100d 内接受 ITS-CL 联合治疗的奶牛发生乳腺炎的 RR 分别为 0.26（95%CI：0.16-0.44）、0.37（0.24-0.57）和 0.72（0.55-0.96），而仅接受 CL 治疗的奶牛为 0.26（95%CI：0.16-0.44）、0.37（0.24-0.57）和 0.72（0.55-0.96）。与单独使用 CL 相比，干奶牛联合 ITS-CL 治疗与亚临床乳腺炎（SCC≥250,000 个细胞/mL）的减少有关[RR=0.80（95%CI：0.65-0.98）]。在之前泌乳期有亚临床乳腺炎病史的奶牛中，联合使用 ITS 和 CL 干奶牛治疗与临床和亚临床乳腺炎的发生率显著降低。
