大肠杆菌性乳房炎奶牛血浆的比较蛋白质组研究

大肠杆菌是奶牛乳房炎的主要病原微生物之一,为了分析大肠杆菌性乳房炎奶牛血浆蛋白的表达变化,探索其防御机制。通过乳汁微生物培养的方法选择仅由大肠杆菌自然感染的隐性乳房炎奶牛。采用二维凝胶电泳技术分离大肠杆菌性乳房炎奶牛和临床健康奶牛的血浆蛋白和ProteoMiner试剂盒富集的中低丰度蛋白,凝胶用考马斯亮蓝G-250染色后,用图像分析软件检测血浆表达的差异蛋白点并用液质联用质谱鉴定。结果发现,大肠杆菌性乳房炎奶牛血浆中有19个蛋白点的表达量发生改变,其中15个蛋白点鉴定为7种蛋白质。在大肠杆菌性乳房炎奶牛血浆中结合珠蛋白、α1酸性糖蛋白和血清淀粉样蛋白A等蛋白的表达量增加。并用ELISA法测定血浆结合珠蛋白的结果也发现,大肠杆菌性乳房炎奶牛血浆结合珠蛋白水平显著高于健康牛(P0.01)。表明大肠杆菌感染造成了奶牛血浆蛋白的表达发生了变化,对这些表达变化蛋白的解析有利于探索机体的防御机制,同时为疾病的诊断和治疗提供科学依据。     

健康奶牛与临床型乳腺炎奶牛乳腺核蛋白组差异表达分析

亚细胞蛋白质组的优点在于对低丰度蛋白的研究,运用亚细胞蛋白质组学的研究策略,可以提高低丰度蛋白质在双向电泳中的检出数量.通过分析奶牛乳腺炎乳腺与正常乳腺核蛋白组差异表达情况,为奶牛乳腺炎发病机理研究寻找尽可能多的生物标记分子.经超速离心法分离细胞核,双向凝胶电泳分离蛋白,用PDQuest7.4软件分析寻找差异蛋白质斑点,高效液相色谱串联离子阱质谱鉴定蛋白质.从核蛋白组2-DE图谱中筛选出22个差异表达的蛋白质斑点,质谱鉴定出17个差异表达的蛋白质,2个蛋白质在乳腺炎发病过程中下调,7个上调,5个只在正常情况下表达,3个只表达在乳腺炎组织中,筛选出的差异表达蛋白质涉及细胞骨架构成、代谢调节及凋亡调控等许多方面.表明奶牛乳腺炎发生时乳腺组织核结构和代谢状态都发生了的变化.     

分娩前后奶牛血浆差异表达蛋白初步分析

本研究运用双向电泳方法分析奶牛产前及产后1周血浆蛋白的差异表达,为理解围产期免疫抑制以及分娩前后奶牛的生理状态提供参考。血浆样品经过热SDS法处理后,使用pH4～pH7的胶条,在硝酸银染色的7.5%～17.5%的梯度聚丙烯酰胺凝胶上,利用PDQuest6.0图像分析软件检测到239个蛋白质点。比较奶牛产前及产后1周血浆蛋白差异表达情况发现,表达量变化3倍以上的点有12个。MADIL-TOF/TOF质谱鉴定出2种蛋白:白蛋白和结合珠蛋白。结合珠蛋白在产后1周的奶牛血浆中的含量显著增加,反映了产后奶牛的生理变化。但是需要结合其他标记共同作为疾病诊断的标记。     

健康奶牛与临床型乳腺炎奶牛乳腺线粒体蛋白组差异表达分析

运用亚细胞蛋白质组学的研究策略,分离纯化亚细胞结构再进行蛋白质组学研究,可提高低丰度蛋白在双向凝胶电泳中的检出率。通过对比分析乳腺炎奶牛乳腺与正常奶牛乳腺线粒体蛋白质组的表达变化,为奶牛乳腺炎的生物学治疗及抗病育种工作筛选出目基因和蛋白。超速离心法分离线粒体,双向凝胶电泳分离蛋白,PDQuest7．4软件分析差异蛋白斑点,高效液相色谱串联离子阱质谱鉴定差异蛋白。从奶牛乳腺线粒体蛋白2-DE图谱中筛选出17个差异表达的蛋白质斑点,质谱鉴定出17个差异表达蛋白（6个蛋白在奶牛乳腺炎发生过程中下调,8个上调,1个只在正常情况下表达,2个只在乳腺炎乳腺组织中表达）。筛选出的差异蛋白质涉及到细胞的能量代谢、蛋白质合成、mRNA的加工成熟及调亡调控等许多方面,表明奶牛乳腺炎发生时乳腺线粒体组织结构和代谢状态都发生了明显的变化。     

牦牛卵泡液差异蛋白质组双向电泳图谱的构建与质谱分析

从蛋白质水平了解牦牛季节性繁殖规律,利用双向电泳与质谱鉴定技术分析牦牛卵泡液与血浆蛋白质组分变化。以青海高原牦牛卵泡液与血浆为研究对象,采用双向电泳技术构建牦牛卵泡液与血浆蛋白质双向电泳图谱,银染后利用Image Master 2D Platinum软件分析并采用MALDI-TOF-MS进行质谱鉴定。用试剂盒ProteoExtract Albumin/IgG Removal Kit去除高丰度蛋白质后,利用2-DE技术获得了分辨率较高的卵泡液与血浆蛋白质电泳图谱,卵泡液与血浆蛋白质图谱对比分析共发现了24个差异表达蛋白质点,其中2个蛋白质点表达上调,22个蛋白质点表达下调。经质谱分析,最终成功鉴定出8个蛋白质点、5个未知蛋白质点。本研究成功构建了蛋白质图谱及分离鉴定的差异蛋白质,为从蛋白质水平揭示牦牛卵泡发育规律及了解卵母细胞发育的微环境提供了试验依据。     

丝氨酸蛋白抑制剂与围产期奶牛血钙的关系

本研究旨在了解围产期低血钙奶牛与正常奶牛的血浆Serine peptidase inhibitor(SERPIN)与血钙之间的关系。在分娩当天、产前14～7d和产后7～14d根据血钙浓度将实验牛分为正常对照组(2.20～3.5mmol/L,C)和低血钙组(<2.20mmol/L,T),每组3头。利用Westernblotting检测试验牛血浆SERPIN丰度。结果显示:SPI蛋白在奶牛发生低血钙时,表达上调。结论:本试验首次证明了血浆SERPIN与血钙浓度呈负关联,血钙可能通过SERPIN途径调节机体的凝血过程和免疫功能。     

不同条件对鸭瘟病毒感染细胞蛋白质组二维电泳分析结果的影响

本研究以鸭瘟病毒感染鸭胚成纤维细胞为材料,围绕影响二维电泳因素进行全面探讨,以建立和优化鸭瘟病毒感染细胞蛋白质组二维电泳模型.结果表明,样品经过冷丙酮处理,水化液DTT浓度为30 mmol/L都有利于等电聚焦;采用PH5～8 IPG窄胶条和混合两性裁体电解质pH3～10/pH5～8为2/1比pH3～10 IPG宽胶条和单一两性载体电解质PH3～10分离蛋白时,各蛋白点间距较大,分辨率高,更有利于显示低丰度蛋白点;1.5 mg的蛋白上样量偏大,2～DE图像出现拖尾和水平条纹,部分相邻高丰度的蛋白重叠,且还掩盖了低丰度蛋白点.PDQuest7.40软件分析显示:17 cm PH5～8 IPG胶条电泳鸭瘟病毒感染细胞蛋白质组,银染可获得1 253个蛋白点,而考染却检测到388个蛋白点;重复试验仍获得清晰、稳定的2-DE图像,同一样本不同时期,考染可获得约348、331个蛋白点,蛋白点匹配率达88%,表明了鸭瘟病毒感染细胞蛋白质组二维电泳模型稳定、分辨率高、重复性好,为鸭瘟病毒蛋白组的进一步研究和新蛋白的发现提供了重要的研究方法.     

基于SELDI-TOF-MS技术的奶牛乳热血浆蛋白质组学分析

奶牛乳热是围产期奶牛营养代谢性疾病,对于奶牛乳热在病理方面少有血浆蛋白质组学的研究。本研究目的是探究奶牛乳热在蛋白质组学层面的变化。试验21头患有奶牛乳热的奶牛和59头健康奶牛作为试验动物。试验通过SELDI-TOF-MS技术检验得到24个差异肽段的峰值,其中10个肽段经过Swissport Protein数据库搜索鉴定为10种差异蛋白。结果相对于对照组,乳热组中表达上调的蛋白4个;表达下调的蛋白2个;还有既表达上调又表达下调的蛋白4个。结论本次试验应用SELDI-TOF-MS技术鉴定了几个在奶牛发生乳热时表达的差异蛋白质。这些发现也为以后揭示奶牛乳热代谢性改变提供了依据。     

健康与患布鲁菌病奶牛血清蛋白2-DE的建立和初步分析

采用商业化试剂盒Albumin & IgG Depletion Spintrap处理奶牛血清样品,比较处理前后对2-DE图谱的影响,结果发现处理后奶牛血清2-DE图谱中高丰度蛋白明显减少,但低丰度蛋白也有损失.采用不去除高丰度蛋白的方法比较健康奶牛与感染布鲁杆菌病奶牛的血清2-DE图谱,发现了11个明显差异的蛋白点,其中3个在正常奶牛血清中高表达,1个只在正常奶牛血清中表达;6个在患布鲁菌病奶牛血清中高表达,1个只在患布鲁菌病奶牛血清中表达.这些差异蛋白点的发现为将来质谱分析奠定基础.     

奶牛不同乳腺健康状态下乳清蛋白的差异性表达研究

本试验旨在通过研究奶牛不同乳腺健康状态下乳清蛋白差异性表达,探究奶牛乳腺健康状况对乳清蛋白的影响以及病原微生物蛋白诱发炎症的分子机制,为诊断奶牛乳腺健康程度以及早期炎症的发生提供潜在生物标记物。选择102头荷斯坦奶牛[胎次2～3胎、泌乳天数(152±27) d、产奶量(27±3) kg/d]进行牛奶样本采集,根据乳体细胞数(SCC)及细菌学鉴定结果将牛奶样本分为6组,分别为细菌培养阳性组(传染型、环境型和机会型)和细菌培养阴性组[培养阴性-低SCC组(SCC100 000个/mL)、培养阴性-中等SCC组(SCC为100 000～400 000个/mL)和培养阴性-高SCC组(SCC400 000个/mL)]。采用十二烷基硫酸钠-聚丙烯酰胺凝胶电泳(SDS-PAGE)与非标记定量蛋白质组学等技术对6组乳清样本中的蛋白质功能及表达水平进行鉴定。结果表明:1)奶牛健康乳腺与炎症乳腺之间的差异主要是由蛋白质的表达水平造成的。2)试验总共鉴定出272种蛋白质,其中有58种蛋白质显示出显著调节变化。与细菌培养阴性乳清样本相比,细菌培养阳性乳清样本中有20种蛋白质表达显著上调(P0.05),其中导管素-4(CATHL4)、导管素-3(CATHL3)、导管素-2(CATHL2)、α-球蛋白抑制因子H4(ITIH4)、丝氨酸蛋白酶抑制剂A3-1(SERPINA3-1)、前列腺素H-2 D异构酶(PTGDS)、血清淀粉样蛋白A3(SAA3)和免疫球蛋白κv3-20(IGKV3-20)在培养阳性乳清样本中的表达量超过培养阴性乳清样本的约8倍,且上调蛋白质的功能多数与特异性免疫反应有关。显著或极显著下调的蛋白质有38种(P0.05或P0.01),其中血小板糖蛋白4(CD36)、补体蛋白CD59(CD59)、κ酪蛋白(CSN3)、嗜乳脂蛋白亚家族1成员A1(BTN1A1)、ATP结合盒转运蛋白G2(ABCG2)、围脂滴蛋白2(PLIN2)、包膜糖蛋白2(GP2)、聚泛素-C(UBC)和异柠檬酸脱氢酶1(IDH1)呈现极显著下调(P0.01),BTN1A1与脂质合成和分泌有关,PLIN2和GP2与转运有关,ABCG2具有酶活性,CD59与免疫系统有关。3)在细菌培养阳性乳清样本中鉴定到21种菌体蛋白,这些菌体蛋白的存在既验证了细菌培养鉴定结果,又从菌体蛋白特性和功能角度阐明了病原微生物诱发炎症的分子机制。综上所述,通过对奶牛不同乳腺炎症状态下乳蛋白差异表达研究,根据不同炎症类型奶样中乳蛋白质及菌体蛋白的表达变化及功能揭示了不同乳腺健康状态下乳腺内的生物学现象,此外为诊断乳腺健康特别是早期乳腺炎症的发生提供潜在生物标记物。     

Proteomic analysis of plasma from cows affected with milk fever using two-dimensional differential in-gel electrophoresis and mass spectrometry

Milk fever is an important metabolic disorder of dairy cows after calving, and is characterized by hypocalcemia, tetany, lateral recumbency, and eventual coma. To date, there have been many reports about the pathogenesis and pathophysiology of milk fever, but the plasma protein profile in milk fever has not been reported. The aim of our study was to investigate novel pathophysiological changes in the plasma proteome of cows affected with milk fever. Plasma samples were collected from eight Holstein cows with milk fever (T), and eight control Holstein cows without milk fever (C), at an intensive Holstein dairy farm in Heilongjiang province, China. Samples were analyzed by fluorescence two-dimensional (2D) differential in-gel electrophoresis (DIGE), followed by in-gel digestion, and matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF-MS) for peptide mass fingerprinting of selected protein spots. Eight of the 23 differential protein spots in the plasma of T and C cows were isolated and identified by 2D-DIGE and MALDI-TOF-MS. The protein spots represented five unique proteins, and had significant alterations in spot volume as determined by DeCyder differential in-gel analysis (DIA) software. The upregulated proteins were identified as serpin peptidase inhibitor (angiotensin), which regulates blood pressure and maintains fluid and electrolyte homeostasis, and endopin 2B which is involved in neural regulation. The downregulated proteins were serum albumin, which acts as a transport protein, fibrinogen beta chain which is involved in blood coagulation, and IgG heavy-chain C-region (IgG-C(H)) which participates in the immune response. In conclusion, we were able to use proteomic technologies to identify several novel plasma proteins in cows affected with milk fever. These findings may reveal new pathophysiological changes that occur in cows with milk fever.     

Protein expression in dairy cows with and without subclinical hypocalcaemia

AIM: To determine differences in plasma proteomic profiles between healthy cows and those with subclinical hypocalcaemia within 12 hours after calving, and thereby explore the underlying biological mechanism of subclinical hypocalcaemia in dairy cows.

METHODS: Plasma samples were collected within 6 hours of calving from Holstein cows on a farm in Heilongjiang, China; 32 with subclinical hypocalcaemia (plasma calcium concentration 1.38–2.00?mmol/L and no clinical signs) and 59 control cows (plasma calcium concentration 2.10–2.8?mmol/L). Plasma samples were applied to weak cationic exchange protein chips for protein profiling by surface-enhanced laser desorption/ionisation time-of-flight mass spectrometry (SELDI-TOF-MS), and the data were analysed using the PBS-IIC system. The amplitude of peaks for the two groups were compared using the Wilcoxon sum-rank test, and the mass-to-charge ratio of the peaks that differed was used to identify peptide fragments using the Swiss-Prot protein database.

RESULTS: Seven peaks were identified in the subclinical hypocalcaemia group that differed from those of the control group (p<0.001), that represented six unique proteins. Expression of serum albumin, fibrinogen alpha chain, amyloid beta A4 proteins and neurosecretory protein VGF were increased, and expression of apolipoprotein A-II and serum amyloid A proteins were decreased in the subclinical hypocalcaemic cows compared with control cows.

CONCLUSION: Use of SELDI-TOF-MS technology can effectively identify differences in plasma protein expression patterns in cows with subclinical hypocalcaemia. Neurosecretory protein VGF and amyloid beta A4 protein might represent useful biomarkers for diagnosis of subclinical hypocalcaemia.     

Seroprevalence of Mycobacterium avium subsp paratuberculosis infection among dairy cows in Colorado and herd-level risk factors for seropositivity

OBJECTIVE: To estimate seroprevalence of Mycobacterium avium subsp paratuberculosis (MAP) infection among adult dairy cows in Colorado and determine herd-level factors associated with the risk that individual cows would be seropositive. DESIGN: Cross-sectional observational study. ANIMALS: 10,280 adult (> or = 2 years old) dairy cows in 15 herds in Colorado. PROCEDURE: Serum samples were tested with a commercial ELISA. A herd was considered to be infected with MAP if results of mycobacterial culture of > or = 1 individual cow fecal sample were positive or if > or = 1 culled cow had histologic evidence of MAP infection. RESULTS: 424 of the 10,280 (4.12%) cows were seropositive. Within-herd prevalence of seropositive cows ranged from 0% to 7.82% (mean, 2.6%). Infection was confirmed in 11 dairies. Cows in herds that had imported > or = 8% of their current herd size annually during the preceding 5 years were 3.28 times as likely to be seropositive as were cows in herds that imported < 8%. Cows in herds with > or = 600 lactating cows were 3.12 times as likely to be seropositive as were cows in herds with < 600 lactating cows. Cows in herds with a history of clinical signs of MAP infection were 2.27 times as likely to be seropositive as were cows in herds without clinical signs. CONCLUSIONS AND CLINICAL RELEVANCE: Annual importation rate, herd size, and whether cows in the herd had clinical signs typical of MAP infection were associated with the risk that individual cows would be seropositive for MAP infection.     

奶牛乳腺组织亚细胞组分的双向凝胶电泳分析

利用超速离心结合梯度离心法分离亚细胞组分的技术路线,以提高奶牛乳腺组织蛋白双向凝胶电泳的分离效率。奶牛乳腺组织液氮研磨破碎后,差速离心分离成细胞核、线粒体、高尔基体、溶酶体4个亚细胞组分,Nyco-denz纯化,2-DE分离蛋白,PDQUest8.0软件分析凝胶图谱。结果显示,奶牛乳腺组织细胞经亚细胞分离后,电泳分辨率大大提高,特别是细胞核蛋白质检出效率明显提高。不同亚细胞蛋白质组电泳图谱的差异显示了其蛋白质组构成的不同。由此可见超速离心结合梯度离心是一种有效的奶牛乳腺亚细胞组分分离手段,亚细胞蛋白质组学克服了蛋白质组的一些缺陷并可将蛋白质组研究引向亚细胞水平。     

An evaluation of a modified interferon-gamma assay for the detection of paratuberculosis in dairy herds

Whole blood samples were obtained from multiple dairy herds in Pennsylvannia and in Wisconsin which were previously determined to be infected with Mycobacterium paratuberculosis (MpS) (Johne's disease) by fecal culture. Blood samples were shipped overnight to the National Animal Disease Center (NADC) in Ames, IA for processing and interferon-gamma (IFN-gamma) analysis. Blood samples were incubated alone (non-stimulated) or with concanavalin A (ConA), a T-cell mitogen used as a positive control in the assay, for 18h. In addition, samples were incubated with M. avium purified protein derivative (AvPPD), M. bovis purified protein derivative (BoPPD), or a whole cell sonicate of M. paratuberculosis for 18h to elicit antigen-specific IFN-gamma production. After incubation, plasma was harvested and analyzed for IFN-gamma by ELISA. Values for IFN-gamma for non-stimulated blood samples (background) were consistently low for animals in all herds evaluated. In contrast, ConA stimulation of blood samples evoked a significant secretion of IFN-gamma regardless of infection status or fecal culture results for individual cows, indicating that immune cells were still viable after overnight shipment and capable of responding to stimulation. Antigen-specific IFN-gamma results were positively correlated with infection status as determined by previous fecal shedding and/or current fecal shedding of M. paratuberculosis. Accuracy of the IFN-gamma assay for correctly predicting infection status of individual cows in the herds with low levels of infection ranged from 50 to 75% when used as a single test. Combined use of the IFN-gamma test and a commercial ELISA antibody test accurately predicted infection status of 73% of cows from a dairy herd with a high level of M. paratuberculosis infection and 90% from a well-characterized group of dairy cows at the NADC. These results indicate that the antigen-specific IFN-gamma assay is a very sensitive diagnostic tool for detection of subclinical paratuberculosis in cattle and may be useful on an individual animal basis to remove infected animals from the herd.     

Proteomic analysis of mammary tissues from healthy cows and clinical mastitic cows for identification of disease-related proteins

To investigate the disease-related proteins and understand molecular mechanism of mastitis at the protein level, this project presents the protein changes in the mammary gland between healthy cows and clinical mastitic cows using two-dimensional gel electrophoresis (2-DE), after stained with colloidal Coomassie Bright Blue, six spots of differentially expressed protein were detected by PDQuest software and subjected to ion trap mass spectrometer equipped with a HPLC system, and five proteins were identified. Hemoglobin beta, kappa-casein and tryptophanyl-tRNA-synthetase (TrpRS) in healthy dairy cows, while hemoglobin beta, cytochrome C oxidase and annexin V in clinical mastitic cows were identified, they were involved in binding, transport and catalytic activity. The results may provide valuable information for the investigating of the host mammary immune system response to defense against pathogens at the protein level and potential protein targets for treatment.     

Estimated within-herd prevalence (WHP) of Mycobacterium avium subsp. paratuberculosis in a sample of Minnesota dairy herds using bacterial culture of pooled fecal samples

The objective of this study was to describe the estimated within-herd prevalence (WHP) of Mycobacterium avium subsp. paratuberculosis (Map) in a sample of infected dairy herds in Minnesota (N = 66) using test results from bacterial culture of pooled fecal samples. Fecal samples were collected from up to 100 cows in each herd and were tested using bacterial culture in pools of 5 cows based on age order. The mean herd size was 222 (44 to 1500) milking cows; the cows were predominantly Holstein. Using a frequentist approach, the within-herd mean individual fecal prevalence was 10% [95% confidence interval (CI) = 4% to 16%] assuming 70% test sensitivity and 99.5% test specificity. Using Bayesian methods, the estimated true within-herd individual cow prevalence was 14% (95% CI = 7% to 27%). Within-herd prevalence was higher in larger dairy herds than in herds with fewer cows. As Map is the causative agent of Johne's disease (JD), the results of this study could contribute to the success of a nationwide control program for this disease.     

Prevalence of fecal shedding of Salmonella spp in dairy herds

OBJECTIVE: To estimate prevalence of Salmonella spp in Ohio dairy farms and to identify potential risk factors for fecal shedding of salmonellae. DESIGN: Cross-sectional study. SAMPLE POPULATION: 105 Ohio dairy farms. PROCEDURE: Individual fecal samples from all mature cows in study herds were tested for Salmonella spp by use of standard bacteriologic culture procedures. Herds were identified as infected if at least 1 cow was shedding Salmonella spp. Information regarding herd characteristics, management practices, and health history were collected. Potential risk factors for herd-level Salmonella infection were identified. RESULTS: In 31% of the study herds (95% confidence interval, 22 to 40%), at least 1 cow was shedding Salmonella spp. Six percent of 7,776 fecal samples contained Salmonella organisms; prevalence within infected herds ranged from < 1 to 97%. Herd size, use of free stalls for lactating and nonlactating cows, and use of straw bedding in nonlactating cows were significantly associated with fecal shedding of Salmonella spp, as determined by use of univariate analysis. By use of multivariate analysis, large herds were more likely to be infected than smaller herds; however, no other factors were associated with Salmonella infection after adjustment for herd size. CONCLUSIONS AND CLINICAL RELEVANCE: Subclinical shedding of Salmonella spp is common in Ohio dairy herds, although we could not identify specific interventions that may influence the prevalence of Salmonella spp on dairy farms. It appears that large herd size and intensive management may provide an environment conducive to Salmonella shedding and chronic dairy herd infection.     

Serological survey of bovine herpesvirus type 1 infection in China

To understand the nationwide seroprevalence of bovine herpesvirus type 1 (BoHV-1) infection of cows in China, 1344 sera of dairy cows from 29 provinces and 765 sera from 6 herds in Hubei province were collected with stratified random sampling. Another 483 sera from imported cows were included. The serum antibody was tested by BoHV-1 gG ELISA. The results demonstrated that the overall nationwide seroprevalence was 35.8% (481/1344), while the prevalence for individual province ranged from 12.1% to 77.8%. Although each province had positive samples, the prevalence was clustered in areas based on the cow population size. In Hubei Province, the overall seroprevalence was 22.2% (170/765) while the prevalence for individual farms varied greatly from 0.0% to 41.5%. The sera from imported cows had a moderate prevalence of 21.7% (105/483).     

Persistent fecal Salmonella shedding in five dairy herds

OBJECTIVE: To monitor patterns of Salmonella fecal shedding in naturally infected dairy herds, determine the association between fecal shedding and individual animal production measures, and evaluate potential risk factors for shedding of Salmonella organisms among cattle in dairy herds. DESIGN: Longitudinal study. SAMPLE POPULATION: 5 Ohio dairy herds. PROCEDURE: For 3 herds, fecal samples were collected from all mature cows and unweaned calves 7 times during an 18-month period. For the remaining 2 herds, fecal samples were collected from 50 lactating cows 6 times during a 12-month period. Individual animal production records for 3 herds were used to examine associations between individual fecal Salmonella shedding status and 305-day mature-equivalent milk production, somatic cell count, milk fat content, and milk protein content. Multivariable logistic regression was used to test for associations between fecal shedding status and breed, lactation status, lactation number, and duration of lactation. RESULTS: None of the adult animals had clinical signs of salmonellosis, but prevalence of fecal Salmonella shedding at individual collection times ranged from 0 to 99% for cows and from 0 to 67% for unweaned calves. Mature cows were more likely to be shedding Salmonella organisms than were unweaned calves. Within herds, lactation status and duration of lactation for individual animals were associated with Salmonella shedding status. Salmonella fecal shedding status was not associated with individual cow production measures. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that subclinical fecal Salmonella shedding can persist in dairy herds for up to 18 months with no measurable effects on health or production of individual cows.