Antimicrobial susceptibility of mastitis pathogens isolated from North American dairy cattle, 2011-2022.

A total of 10,890 bacterial isolates of Streptococcus dysgalactiae, Streptococcus uberis, Staphylococcus aureus and Escherichia coli isolated as etiological agents from dairy cows with mastitis by 29 veterinary laboratories across North America between 2011 and 2022 were tested for in vitro antimicrobial susceptibility by broth microdilution to ampicillin, cefoperazone, ceftiofur, cephalothin, erythromycin, oxacillin, penicillin-novobiocin and pirlimycin according to CLSI standards. Using available clinical breakpoints, antimicrobial resistance among S. dysgalactiae (n = 2406) was low for penicillin-novobiocin (0% resistance), ceftiofur (0.1%), erythromycin (3.2%) and pirlimycin (4.6%). Among S. uberis (n = 2398), resistance was low for ampicillin (0%) and ceftiofur (0.2%) and moderate for erythromycin (11.9%) and pirlimycin (18.4%). For S. aureus (n = 3194), resistance was low for penicillin-novobiocin (0%), ceftiofur (0.1%), oxacillin (0.2%), erythromycin (0.7%), cefoperazone (1.2%) and pirlimycin (2.8%). For E. coli (n = 2892), resistance was low for ceftiofur (2.8%) and cefoperazone (3.4%) and moderate for ampicillin (9.2%). Overall, the results indicate that mastitis pathogens in the United States and Canada have not shown any substantial changes in the in vitro susceptibility to antimicrobial drugs over the 12 years of the study, or among that of the proceeding survey from 2002-2010. The data support the conclusion that resistance to common antimicrobial drugs among mastitis pathogens, even to drugs that have been used in dairies for mastitis management for many years, continues to remain low.

Bayesian accuracy estimates of environmental sampling for determining herd paratuberculosis infection status and its association with the within-herd individual fecal culture prevalence in Québec dairies.

The objectives of this retrospective analysis were to: 1) estimate the diagnostic sensitivity (Se) and specificity (Sp) of bacterial culture of environmental samples for determining Mycobacterium avium subsp. paratuberculosis (MAP) infection status in Québec dairies, using a Bayesian Latent Class Model (BLCM); and 2) determine the association between the number of positive environmental samples and the individual fecal culture (IFC) apparent and true MAP within-herd prevalence. Environmental and individual fecal samples were collected from 87 commercial dairy herds participating in previous research projects. Environmental samples included two composite samples of 20 g collected from different locations within each of the following sites: an area where manure from the majority of adult cattle accumulates, a manure storage area and another site of manure accumulation chosen by the veterinarian. Samples were cultured using the MGIT Para TB culture liquid media and the BACTEC MGIT 960 system. The Se and Sp of environmental sampling were estimated using a one-test-one-population BLCM. Herds were considered positive for environmental sampling if at least one out of the six samples collected was positive. The apparent and true IFC within-herd MAP prevalence estimates for each herd were obtained using a two-stage cluster BLCM, then merged in a single dataset with the environmental sample results. The association between the within-herd MAP prevalence results (apparent and true), and the number of positive environmental samples was assessed using a zero-inflated negative binomial (ZINB) model. In all BLCMs, median posterior estimates and 95 % Bayesian credible intervals (BCI) were obtained with OpenBUGS statistical freeware. Se and Sp of environmental sampling were 43.7 % (95 % BCI: 32.5-55.5) and 96.2 % (95 % BCI: 84.2-99.8), respectively. Overall, the number of positive environmental samples increased with the apparent and true MAP within-herd prevalence. The true prevalence was higher than the apparent prevalence for a given number of positive environmental samples. The probability of not observing a positive environmental sample decreased with the prevalence. Despite its imperfect accuracy, environmental sampling is an inexpensive and non-invasive sampling method to determine MAP infection status in tie-stall herds that can be used as a proxy to estimate the true within-herd prevalence. The absence of positive environmental samples in a single sampling visit is likely an indicator of a very low within-herd prevalence rather than being MAP exempt.

Risk factors associated with Mycobacterium avium subsp. paratuberculosis herd status in Québec dairy herds.

Paratuberculosis is a chronic and contagious enteric disease of ruminants caused by Mycobacterium avium subsp. paratuberculosis (MAP). Control of paratuberculosis is justified given the associated economic losses and the potential role of MAP in Crohn's disease in humans. Management practices that limit exposure of susceptible animals to MAP are more effective at reducing disease prevalence than testing and culling infected cows. The objective of this retrospective case-control study was to study the association between management practices and MAP status in dairy herds in Québec, Canada. A total of 26 case herds (MAP had been isolated from at least 1 environmental sample in each herd) and 91 control herds (no clinical cases of paratuberculosis and negative on 2 consecutive yearly environmental samplings) were selected among herds enrolled in the Québec Voluntary Paratuberculosis Control Program. A risk assessment questionnaire, completed at enrolment, was available for the selected herds. Culture of MAP was achieved using liquid media and the BACTEC 960 detection system. Multivariable logistic regression was used to evaluate the association between selected risk factors and MAP herd status. Herd size (OR = 1.17; 95% CI: 1.02-1.33) and proportion of cows purchased per year in the last 5 years (OR = 5.44; 95% CI: 1.23-23.98) were significantly associated with a positive MAP herd status. The management risk factors identified in the present study are in accord with previous studies. Management practices aiming to prevent the introduction of new animals into the herd and to reduce the contact of newborn calves with adult animals or their feces are key elements to minimize MAP introduction and transmission into a herd. These elements should be prioritized in control programs.

Long-term mechanical milking status of lacerated teat repaired surgically in cattle: 67 cases (2003-2013).

This study evaluated the long-term prognosis of return to normal mechanical milking after reconstructive teat surgery and determined the factors that have an impact on the outcome. A retrospective study of 67 dairy cows with teat lacerations was performed. Milking status at discharge and at long-term follow-up was adequate for 83% and 75% of the cows, respectively. No statistically significant differences were detected between the long-term prognosis and the age of the cow, the stage of lactation at presentation, or the configuration of the laceration. Lacerations repaired more than 24 hours after the trauma were more frequently associated with a negative outcome (P = 0.05). Mastitis was the most frequent complication (n = 17) and had a statistically significant negative impact on long-term prognosis (P = 0.02). Reconstructive surgery of lacerated teat in dairy cows can help establish return to normal mechanical milking.

Évaluation du pronostic à long terme en regard de la traite mécanique des trayons lacérés réparés chirurgicalement chez la vache : 67 cas (2003­2013). Les objectifs de cette étude sont d'évaluer le pronostic à long terme, en regard de la traite mécanique, suivant la reconstruction d'un trayon lacéré et de déterminer les critères associés à un pronostic négatif. Une étude rétrospective sur 67 vaches laitières a été réalisée. La traite mécanique était adéquate pour 83 et 75 % des vaches à leur sortie de l'hôpital et lors du suivi à long terme. Pas de différences statistiques ont été trouvées entre le pronostic à long terme et l'âge des vaches, leur stade de lactation et la configuration de la lacération. Les lacérations réparées plus de 24 heures après le trauma avaient un pronostic moins bon (P = 0,05). La complication la plus fréquente était la mammite (n = 17). Elle avait un effet négatif sur le pronostic à long terme (P = 0,02). Reconstruire chirurgicalement un trayon lacéré peut rétablir la traite mécanique.(Traduit par les auteurs).

Detection of Mycobacterium avium subspecies paratuberculosis in tie-stall dairy herds using a standardized environmental sampling technique and targeted pooled samples.

Mycobacterium avium ssp. paratuberculosis (MAP) is the etiologic agent of Johne's disease, a chronic contagious enteritis of ruminants that causes major economic losses. Several studies, most involving large free-stall herds, have found environmental sampling to be a suitable method for detecting MAP-infected herds. In eastern Canada, where small tie-stall herds are predominant, certain conditions and management practices may influence the survival and transmission of MAP and recovery (isolation). Our objective was to estimate the performance of a standardized environmental and targeted pooled sampling technique for the detection of MAP-infected tie-stall dairy herds. Twenty-four farms (19 MAP-infected and 5 non-infected) were enrolled, but only 20 were visited twice in the same year, to collect 7 environmental samples and 2 pooled samples (sick cows and cows with poor body condition). Concurrent individual sampling of all adult cows in the herds was also carried out. Isolation of MAP was achieved using the MGIT Para TB culture media and the BACTEC 960 detection system. Overall, MAP was isolated in 7% of the environmental cultures. The sensitivity of the environmental culture was 44% [95% confidence interval (CI): 20% to 70%] when combining results from 2 different herd visits and 32% (95% CI: 13% to 57%) when results from only 1 random herd visit were used. The best sampling strategy was to combine samples from the manure pit, gutter, sick cows, and cows with poor body condition. The standardized environmental sampling technique and the targeted pooled samples presented in this study is an alternative sampling strategy to costly individual cultures for detecting MAP-infected tie-stall dairies. Repeated samplings may improve the detection of MAP-infected herds.

Mycobacterium avium ssp. paratuberculosis (MAP) est l'agent étiologique de la maladie de Johne, une entérite chronique contagieuse des ruminants et responsable d'importantes pertes économiques. Plusieurs études, la plupart réalisées dans des grands troupeaux en stabulation libre, ont démontré que la technique de culture de prélèvements de l'environnement est appropriée pour la détection des troupeaux infectés par MAP. Dans l'est du Canada où prédominent les petits troupeaux en stabulation entravée, certaines conditions et pratiques de régie pourraient avoir un impact sur la survie, la transmission et l'isolement de MAP. Notre objectif était d'estimer la performance d'une technique standardisée de culture de prélèvements de l'environnement combinée à des échantillons groupés ciblés pour la détection des troupeaux laitiers en stabulation entravée infectés par MAP. Vingt-quatre troupeaux (19 infectés et 5 non infectés) ont été enrôlés, mais seulement 20 troupeaux ont été visités 2 fois dans la même année pour y prélever 7 échantillons de l'environnement et 2 échantillons groupés (vaches malades et vaches maigres). Des échantillons individuels de toutes les vaches dans le troupeau ont été également prélevés. L'isolement de MAP a été réalisé en utilisant le milieu de culture MGIT ParaTB et le système de détection BACTEC 960. Globalement, MAP a été isolée dans 7 % des cultures de l'environnement. La sensibilité de la technique était de 44 % (IC 95 % : 20 % à 70 %) en combinant le résultat des 2 visites et de 32 % (IC 95 % : 13 % à 57 %) en utilisant aléatoirement le résultat d'une seule visite. La meilleure stratégie d'échantillonnage était la combinaison des échantillons de la fosse, de l'écureur, du groupe de vaches malades et du groupe de vaches maigres. La technique standardisée de prélèvements de l'environnement combinée aux échantillons groupés ciblés présentée dans cette étude est une alternative économique à la culture individuelle pour détecter des troupeaux laitiers infectés par MAP. La répétition des prélèvements pourrait contribuer à améliorer la détection des troupeaux infectés par MAP.(Traduit par les auteurs).

A systematic review of risk factors associated with the introduction of Mycobacterium avium spp. paratuberculosis (MAP) into dairy herds.

The objective of this study was to systematically collect and appraise the scientific evidence related to risk factors associated with the introduction of Mycobacterium avium spp. paratuberculosis (MAP) into a herd of cattle. An electronic search was conducted to collect relevant references addressing 2 specific questions: are i) purchasing/introduction of cattle into a herd, and ii) presence of wildlife or domestic animals, risk factors for the introduction of MAP into a herd? The screening was based on titles and abstracts and selected studies were fully analyzed. Seventeen manuscripts published between 1996 and 2011 were ultimately analyzed. Unit of interest was mainly the herd (n = 17). The specific description of the risk factors studied varied between studies. The principal study design was cross-sectional (n = 15). The review indicated that purchase/introduction of animals was an important risk factor and that the importance of wildlife or other domestic species as a mechanism for transmission into a cattle herd was not measurable.

Revue systématique sur les facteurs de risque associés à l'introduction deMycobacterium aviumspp.paratuberculosis(MAP) dans les troupeaux laitiers. L'objectif était la collecte et l'évaluation systématique des preuves scientifiques liées à des facteurs de risque associés à l'introduction de Mycobacterium avium spp. paratuberculosis (MAP) dans un troupeau.Une recherche électronique a été réalisée pour trier des publications afin de répondre à 2 questions : Est-ce que i) l'achat/introduction de bovins dans un troupeau, et ii) la présence d'animaux sauvages et domestiques sont des facteurs de risque pour l'introduction de MAP dans un troupeau. La sélection a été effectuée en se basant sur les titres, les résumés, et les études choisies ont été entièrement analysés.Dix-sept manuscrits publiés entre 1996 et 2011 ont été sélectionnés. L'unité d'intérêt a principalement été le troupeau (n = 17). Les descriptions des facteurs de risque étudiés variaient d'une étude à l'autre. La majorité des études étaient de type transversal (n = 15).L'achat d'animaux est un facteur de risque bien documenté confirmant l'introduction de la paratuberculose dans le troupeau. Toutefois, malgré la présence de MAP dans les populations domestiques et sauvages à proximité du bétail, l'importance de ce facteur de risque dans la transmission à un troupeau n'était pas mesurable.(Traduit par les auteurs).

Validation of the handheld Lactate-Pro analyzer for measurement of blood L-lactate concentration in cattle.

BACKGROUND: Blood L-lactate concentration (LAC) can be used for various diagnostic purposes in cattle. As multiple handheld analyzers for LAC exist, it is important to validate their use in cattle in comparison with reference laboratory blood analyzers. OBJECTIVES: The objectives of this study were to validate the handheld Lactate Pro meter (LacP) including reproducibility, and compare the measurements with the StatProfile (StatP) as a gold standard. In addition, diagnostic sensitivity and specificity, and the impact of HCT on LAC measured by both analyzers were assessed. METHODS: A cohort of 64 cattle with acute medical and surgical conditions was studied. Whole blood samples in heparin lithium tubes were analyzed upon arrival with both StatP and LacP. Twenty-three samples were immediately retested to assess intra-assay coefficient of variation (CV). The HCT values were also recorded. RESULTS: The LAC using LacP was highly correlated with the StatP (r = 0.9736 [95% confidence interval [CI]: 0.9562-0.9841]). The LacP underestimated LAC (mean difference:-0.9 mmol/L, 95% CI:-3.1 mmol/L to 1.3 mmol/L). The intra-assay CV was excellent (4.77%). No significant correlation was observed between LacP or StatP and HCT (P = .39 and .09, respectively). Sensitivity and specificity for LacP were 91.7% (95% CI: 76.4-97.8%) and 100% (83.4-100%, cutoff of 4 mmol/L), and 78.6% (58.5-90.9%) and 100% (87.0-100%, cutoff of 6 mmol/L). CONCLUSIONS: The LacP handheld lactate meter can be used safely and reliably cow-side, although it underestimates LAC value when compared with a standard laboratory analyzer especially for LAC ≥ 10.0 mmol/L. The LAC value was not influenced by HCT in this study.

Duodenal obstruction caused by duodenal sigmoid flexure volvulus in dairy cattle: 29 cases (2006-2010).

OBJECTIVE: To characterize duodenal sigmoid flexure volvulus (DSFV) and determine the prognosis for affected cattle undergoing surgery. DESIGN: Retrospective case series. ANIMALS: 29 dairy cattle. PROCEDURES: The medical records were analyzed for history, signalment, clinical signs, medical management, surgical findings, and outcome. RESULTS: 29 cattle were determined to have DSFV between December 2006 and August 2010. Twenty cattle had had an omentopexy or pyloropexy performed 1 day to 2 years before initial evaluation. Cattle were afebrile, tachycardic, and moderately dehydrated, with a small zone of percussion with a ping at the 10th to 12th right intercostal spaces and associated succussion. Biochemical changes were a severe hypokalemic (mean ± SD, 2.9 ± 0.5 mmol/L; median, 3.1 mmol/L; range, 2.08 to 3.92 mmol/L), hypochloremic (mean, 69.7 ± 11.1 mmol/L; median, 71.7 mmol/L; range, 49.1 to 94.1 mmol/L) metabolic alkalosis (mean total CO(2), 44.5 ± 7.4 mmol/L; median, 45.3 mmol/L; range, 31.5 to 59.6 mmol/L) and hyperbilirubinemia (mean, 32.4 ± 29.0 µmol/L; median, 20.5 µmol/L; range, 7.8 to 107 µmol/L). Surgical findings for DSFV included an empty descending duodenum adjacent to a dorsally displaced and dilated cranial segment of the duodenum, distended abomasum and gallbladder, and a tight volvulus at the base of the duodenal sigmoid flexure. Manual reduction was considered successful if the descending duodenum filled after cranial duodenal massage. Twenty-two patients were successfully treated; the remaining 7 died or were euthanized within 4 days after surgery. CONCLUSIONS AND CLINICAL RELEVANCE: A condition clinically resembling abomasal volvulus but affecting the duodenal sigmoid flexure has been recognized in dairy cattle. When a focal, dorsal right-sided ping and succussion are present combined with severe hypokalemic, hypochloremic metabolic alkalosis and high bilirubin concentration, DSFV should be suspected, especially when there is a history of prior abomasal fixation. After surgical correction, the prognosis is fair to good.

A retrospective study of 29 cases of otitis media/interna in dairy calves.

Epidemiological data, clinical findings, laboratory data, medical imaging, and outcomes were reviewed in 29 dairy calves with otitis media/interna. Age at admission ranged from 1 to 24 wk. The majority of calves were referred during winter. Clinical signs included drooping ear, ptosis, head tilt, abnormal nystagmus, strabismus, dysphagia, regurgitation, stiff neck, opisthotonos, facial hyperesthesia, and purulent aural discharge. Intranasal endoscopic examination of 5 animals revealed nasopharyngeal collapse in 4. Cerebrospinal fluid (CSF) was abnormal in all of 7 cases. Mycoplasma bovis was cultured from all but 1 case with external ear or tympanic bullae samples (n = 12), and Mycoplasma arginini was cultured from the remaining ear sample. Radiographs of the tympanic bullae were performed in 24 calves, tomodensitometry (CT) in 3 calves and ultrasound in 4 calves. According to medical imaging techniques or necropsy, 69% of the cases were classified as chronic. Mean duration of treatment was 23.3 d. The rate of clinical recovery was 75%.Epidemiological data, clinical findings, laboratory data, medical imaging, and outcomes were reviewed in 29 dairy calves with otitis media/interna. Age at admission ranged from 1 to 24 wk. The majority of calves were referred during winter. Clinical signs included drooping ear, ptosis, head tilt, abnormal nystagmus, strabismus, dysphagia, regurgitation, stiff neck, opisthotonos, facial hyperesthesia, and purulent aural discharge. Intranasal endoscopic examination of 5 animals revealed nasopharyngeal collapse in 4. Cerebrospinal fluid (CSF) was abnormal in all of 7 cases. Mycoplasma bovis was cultured from all but 1 case with external ear or tympanic bullae samples (n = 12), and Mycoplasma arginini was cultured from the remaining ear sample. Radiographs of the tympanic bullae were performed in 24 calves, tomodensitometry (CT) in 3 calves and ultrasound in 4 calves. According to medical imaging techniques or necropsy, 69% of the cases were classified as chronic. Mean duration of treatment was 23.3 d. The rate of clinical recovery was 75%.

RésuméÉtude rétrospective de 29 cas d'otite moyenne/interne chez les veaux laitiers. Les données épidémiologiques, les signes cliniques, les résultats de laboratoire et d'imagerie médicale et l'évolution de 29 veaux atteints d'otite moyenne/interne sont présentés. L'âge à la présentation variait de 1 à 24 semaines. La majorité des veaux ont été admis en hiver. Les signes cliniques incluaient une oreille tombante, une ptose de la paupière, une tête penchée, un nystagmus pathologique, un strabisme, de la dysphagie, des régurgitations, une raideur cervicale, de l'opisthotonos, de l'hyperesthésie faciale et une écoulements purulente de l'oreille. L'endoscopie des voies respiratoires supérieures a révélé un collapse du nasopharynx dans 4 cas sur 5. L'analyse du liquide céphalo-rachidien était anormale chez 7 veaux. Mycoplasma bovis a été isolé de tous les cas à partir d'échantillons d'oreille externe ou de bulle tympanique sauf 1 (n = 12) où Mycoplasma arginini a été isolé. La radiographie des bulles tympaniques a été réalisée sur 24 cas, la tomodensitométrie sur 3 cas et l'échographie sur 4 cas. Selon les techniques d'imagerie médicale ou la nécropsie, 69 % des cas étaient chroniques. La durée moyenne du traitement était de 23,3 jours. Le pronostic était de 75 %.(Traduit par les auteurs).

Congenital enlargement of the suburethral diverticulum in a Holstein calf.

A 3-month-old, female Holstein calf was examined because of marked perineal swelling and tenesmus of 4-days duration. A congenitally enlarged urethral diverticulum was diagnosed using fluoroscopic and ultrasonographic imaging techniques. The urethral diverticulum was surgically resected and the perineal area was reconstructed.

Pharmacokinetics of ceftiofur crystalline free acid after single subcutaneous administration in lactating and nonlactating domestic goats (Capra aegagrus hircus).

Six nonlactating and six lactating adult female goats received a single subcutaneous injection of ceftiofur crystalline free acid (CCFA) at a dosage of 6.6 mg/kg. Blood samples were collected from the jugular vein before and at multiple time points after CCFA administration. Milk samples were collected twice daily. Concentrations of ceftiofur and desfuroylceftiofur-related metabolites were measured using high-performance liquid chromatography. Data were analyzed using compartmental and noncompartmental approaches. The pharmacokinetics of CCFA in the domestic goat was best described by a one compartment model. Mean (±SD) pharmacokinetic parameters were as follows for the nonlactating goats: area under the concentration time curve(0-∞) (159 h·µg/mL ± 19), maximum observed serum concentration (2.3 µg/mL ± 1.1), time of maximal observed serum concentration (26.7 h ± 16.5) and terminal elimination half life (36.9 h; harmonic). For the lactating goats, the pharmacokinetic parameters were as follows: area under the concentration time curve(0-∞) (156 h·µg/mL ± 14), maximum observed serum concentration (1.5 µg/mL ± 0.4), time of maximal observed serum concentration (46 h ± 15.9) and terminal elimination half life (37.3 h; harmonic). Ceftiofur and desfuroylceftiofur-related metabolites were only detectable in one milk sample at 36 h following treatment. There were no significant differences in the pharmacokinetic parameter between the nonlactating and lactating goats.

Evaluation of the effect of ranitidine on gastroduodenal contractile activity and gastric emptying in horses.

OBJECTIVE: To determine the effect of ranitidine on gastric emptying in horses. ANIMALS: 11 adult horses. PROCEDURES: In vitro, isolated muscle strips from the pyloric antrum and duodenum of 5 horses were suspended in baths and attached to isometric force transducers. Once stable spontaneous contractions were observed, ranitidine or diluent was added at cumulative increasing concentrations. Isometric stress responses were compared. In vivo, 6 horses were assigned to a group in a prospective randomized crossover study design with a wash-out period of 2 weeks between trials. Ranitidine (2.2 mg/kg) or saline (0.9% NaCl) solution was administered IV, and 15 minutes later, acetaminophen (20 mg/kg), diluted in 400 mL of water, was administered via nasogastric tube to evaluate the liquid phase of gastric emptying. Serum acetaminophen concentration was measured at several time points for 3 hours by use of liquid chromatography tandem mass spectrometry. Frequency of defecation was recorded during the 3 hours of the study. RESULTS: Ranitidine increased the contractile activity of the pyloric antrum smooth muscle at a concentration of 10(-4) M. No significant effect of ranitidine on plasma kinetics of acetaminophen was identified. Frequency of defecation did not differ between groups. CONCLUSIONS AND CLINICAL RELEVANCE: Ranitidine did increase gastric motility in vitro, but no effect on liquid phase gastric emptying was identified in healthy horses by use of the acetaminophen absorption model. Results do not support the use of ranitidine to promote gastric emptying.

Liver abscesses in Holstein dairy cattle: 18 cases (1992-2003).

BACKGROUND: The characteristic clinical manifestations, clinicopathologic findings, treatment, and outcome of dairy cattle with liver abscess are poorly defined. ANIMALS: The study included 18 Holstein cows with liver abscesses. METHODS: A retrospective study of medical records was performed. Cattle with liver abscess were identified by ultrasound examination or exploratory laparotomy. RESULTS: The most common reason for examination was anorexia (14/18). Five cows had fever, 5 were bradycardic, and 5 were tachycardic. Peritonitis (n=6) and vagal indigestion (n=4) were the most frequently associated diseases. Neutrophilia (n=14), hyperfibrinogenemia (n=11), and high serum globulin concentration (n=10) were characteristic of chronic inflammation. Evidence of liver disease on serum biochemistry profile was uncommon. The most common bacterium isolated from the abscess was Arcanobacterium pyogenes (n=4). Anaerobic bacteria were isolated frequently (n=7). There were 6 polymicrobial isolates, with both aerobic and anaerobic bacteria, out of 8 positive samples. Medical treatment was successful in 5 of 7 cattle. Five cows were euthanized and postmortem examination revealed 2 cattle with thrombosis of caudal vena cava. CONCLUSIONS AND CLINICAL IMPORTANCE: Holstein dairy cattle affected by liver abscess exhibit no pathognomonic clinical signs. Clinicopathologic findings were often consistent with a chronic active inflammation. Liver abscesses should be included in the differential diagnosis in cattle with a chronic inflammatory process, cranial peritonitis, or vagal indigestion. Prolonged treatment with antimicrobials might be successful.