Diagnostic performance of Mycoplasmopsis bovis antibody ELISA tests on bulk tank milk from dairy herds.

BACKGROUND: Testing of bulk tank milk (BTM) for Mycoplasmopsis bovis (previously Mycoplasma bovis) antibodies is increasingly popular. However the performance of some commercially available tests is unknown, and cutoff values possibly need to be adjusted in light of the purpose. Therefore, the aim of this study was to compare the diagnostic performance of three commercially available M. bovis antibody ELISAs on BTM, and to explore optimal cutoff values for screening purposes. A prospective diagnostic test accuracy study was performed on 156 BTM samples from Belgian and Swiss dairy farms using Bayesian Latent Class Analysis. Samples were initially classified using manufacturer cutoff values, followed by generated values. RESULTS: Following the manufacturer's guidelines, sensitivity of 91.4%, 25.6%, 69.2%, and specificity of 67.2%, 96.8%, 85.8% were observed for ID-screen, Bio K432, and Bio K302, respectively. Optimization of cutoffs resulted in a sensitivity of 89.0%, 82.0%, and 85.5%, and a specificity of 83.4%, 75.1%, 77.2%, respectively. CONCLUSIONS: The ID-screen showed the highest diagnostic performance after optimization of cutoff values, and could be useful for screening. Both Bio-X tests may be of value for diagnostic or confirmation purposes due to their high specificity.

Bayesian evaluation of sensitivity and specificity of blood culture media and hypoglycemia in sepsis-suspected calves.

BACKGROUND: Sepsis is a life-threatening condition for which critically important antimicrobials are often indicated. The value of blood culture for sepsis is indisputable, but appropriate guidelines on sampling and interpretation are currently lacking in cattle. OBJECTIVE: Compare the diagnostic accuracy of 2 blood culture media (pediatric plus [PP] and plus aerobic [PA]) and hypoglycemia for bacteremia detection. Estimate the contamination risk of blood cultures in critically ill calves. ANIMALS: One hundred twenty-six critically ill calves, 0 to 114 days. METHODS: Retrospective cross-sectional study in which the performance of PP, PA and hypoglycemia to diagnose sepsis was assessed using a Bayesian latent class model. A Cox proportional hazards model was used to compare time to positivity (TTP). Potential contamination was descriptively analyzed. Isolates were considered relevant when they were; member of the Enterobacterales, isolated from both blood cultures vials, or well-known, significant bovine pathogens. RESULTS: The sensitivities for PP, PA, and hypoglycemia were higher when excluding assumed contaminants; 68.7% (95% credibility interval = 30.5%-93.7%), 87.5% (47.0%-99.5%), and 61.3% (49.7%-72.4%), respectively. Specificity was estimated at 95.1% (82.2%-99.7%), 94.2% (80.7%-99.7%), and 72.4% (64.6%-79.6%), respectively. Out of 121 interpretable samples, 14.9% grew a presumed contaminant in PA, PP, or both. There was no significant difference in the TTP between PA and PP. CONCLUSIONS AND CLINICAL IMPORTANCE: PA and PP appear to outperform hypoglycemia as diagnostic tests for sepsis. PA seems most sensitive, but a larger sample size is required to verify this. Accuracy increased greatly after excluding assumed contaminants. The type of culture did not influence TTP or the contamination rate.

Long-Term Survival in 241 Cases of Intussusception in Cattle and Factors Associated with Mortality.

Intussusception is a frequent cause of mechanical ileus in cattle. Long-term survival has never been described and risk factors for mortality are scarcely documented. A retrospective cohort study on 241 cattle was conducted to determine survival of intussusception and identify risk factors for mortality. Clinical records were matched with the national cattle identification database. Information on possible predictors including clinical examination, ultrasonography, blood-gas analysis and surgery were collected. Survival analysis and decision tree analysis were used. Overall survival was 44.8% until discharge. Of all animals, 39.0% could complete their life cycle and were eligible for slaughter. Male animals and cattle < 226 days old experienced a significantly higher mortality risk (hazard ratio [HR] = 2.1; 95% confidence interval [CI] = 1.4-3.0 and HR = 2.4; 95% CI = 1.7-3.4, respectively). The final model consisted of heart rate (>95 beats per minute) and packed cell volume (<36.5%) with sensitivity and specificity of 60.4% and 49.4%, respectively. A second model consisted of sex (male) and time to referral (>4.5 days) with sensitivity and specificity of 88.0% and 65.6%, respectively. The long-term prognosis for intussusception in cattle appears to be fair. Factors identified in this study may aid in the decision-making process in cases with presumed intussusception to perform the surgery or opt for euthanasia.

Accuracy and inter-rater agreement among practitioners using quick thoracic ultrasonography to diagnose calf pneumonia.

BACKGROUND: Thoracic ultrasonography (TUS) is a commonly used tool for on-farm detection of pneumonia in calves. Different scanning methods have been described, but the performance of novice practitioners after training has not been documented. METHODS: In this study, 38 practitioners performed quick TUS (qTUS) on 18-23 calves each. Pneumonia was defined as lung consolidation 1 cm or more in depth. Diagnostic parameters (accuracy [Acc], sensitivity [Se] and specificity [Sp]) were compared to those of an experienced operator. Cohen's kappa and Krippendorff's alpha (Kalpha) were determined. The potential effects of training and exam sessions on performance were evaluated. RESULTS: The average relative Se and Sp were 0.66 (standard deviation [SD] = 0.26; minimum [Min.]-Maximum [Max.] = 0-1) and 0.71 (SD = 0.19; Min.-Max. = 0.25-1), respectively. The average relative Acc was 0.73 (SD = 0.11; Min.-Max. = 0.52-0.96). Over all sessions, Cohen's kappa averaged 0.40 (SD = 0.24; Min.-Max. = 0.014-0.90) and Kalpha was 0.24 (95% confidence interval [CI]: 0.20-0.27), indicating 'fair' agreement. Calf age and housing influenced Se and Sp. Supervised practical training improved Se by 17.5% (95% CI: 0.01-0.34). LIMITATIONS: The separate effects of calf age and housing could not be determined. CONCLUSION: This study showed that qTUS, like any other clinical skill, has a learning curve, and variability in performance can be substantial. Adequate training and certification of one's skill are recommended to assure good diagnostic accuracy.

Abomasitis associated with halofuginone intoxication in pre-weaned calves.

BACKGROUND: In this case series abomasitis as a consequence of halofuginone intoxication is suspected. CASE PRESENTATION: Seven Belgian-Blue calves with complaints of anorexia and weight loss were presented to an university clinic. Ultrasonography showed thickening and edema of the abomasal wall in all cases, suggesting abomasitis. Abomasitis was confirmed on necropsy in three cases. Retrospective analysis clarified the uptake of an overdose of halofuginone lactate (348-421 µg/kg/day). Four animals fully recovered after removal of halofuginone lactate administration, therapy for comorbidities (pneumonia, diarrhoea) and supportive therapy. CONCLUSION: To the authors' knowledge, this case series is the first report associating halofuginone lactate use with abomasitis. This was suspected after clinical improvement of four of the presented animals after terminating the administration of a high dose of halofuginone lactate, and exclusion of other possible causes. Underlying mechanisms are still unclear.

Associations of serostatus upon arrival with clinical respiratory disease, lung consolidation and growth in veal calves.

Respiratory tract infections remain a major problem during calf rearing, especially among milk (formula) fed veal. Preconditioning of calves through appropriate colostrum management and vaccination could be helpful to address this issue. The objective of this study was to investigate whether the presence of serum antibodies against major respiratory tract pathogens (Bovine Respiratory Syncytial virus, Parainfluenza 3 virus, Bovine coronavirus, Mycoplasmopsis bovis, Histophilus somni, Pasteurella multocida and Mannheimia haemolytica) and total serum immunoglobulin G (IgG) concentration in calves upon arrival at the veal facility were associated with the occurrence of clinical bovine respiratory disease (BRD) or lung consolidation in the first 3 weeks, as assessed by both the Wisconsin BRD scorecard (based on 5 clinical signs: cough, rectal temperature, ear position, nasal-and ocular discharge) and by quick thoracic ultrasound scanning (qTUS). Additionally, the association between calves' serostatus production parameters were explored. A prospective cohort study was conducted among 442 male dairy calves on a large veal calf facility in Belgium. Both clinical scoring and qTUS were performed on all calves at 4 key moments in the production cycle: arrival at the facility, initiation of first metaphylactic antimicrobial treatment at peak incidence of BRD (wk 1), end of the first metaphylactic treatment (short-term evaluation) and at wk 10 (long-term evaluation). Mixed effects logit regression models were fitted to quantify relationships. The outcomes of interest were clinical respiratory disease (Wisconsin BRD scorecard positive), lung consolidation (≥1cm or ≥ 3cm), average daily weight gain and cold carcass weight. In the first week of production, incidence of lung consolidation (≥1cm) quickly increased from 14.9% upon arrival to 43.0% at the peak of the BRD incidence, while clinical BRD increased from 3.6% to 16.1%. The main finding of this study was that calves who were seropositive for bovine respiratory syncytial virus (BRSV) and bovine coronavirus (BCoV) at arrival had reduced odds of developing lung consolidation at the peak of the outbreak, 0.58 OR (95% CI: 0.38 - 0.89) and 0.37 OR (95% CI: 0.20 - 0.69), respectively. No relationships between serum IgG concentration at arrival and the development of lung consolidations or clinical respiratory disease were found. Nevertheless, on average, throughout the first 10 weeks of the fattening cycle, calves with failed transfer of passive immunity (FPT, serum IgG < 7.5 g/L) gained 40 g/day (95% CI: 10-70g/day) less weight (ADG). Hence, ensuring that calves have a positive serostatus for these respiratory tract pathogens before entering the facility may help lower the incidence of lung consolidations, subsequently reducing treatment incidence and the adverse effects on primary economic outcomes.

Differentiating airway inflammation in calves based on cluster analysis of bronchoalveolar lavage fluid cytology.

BACKGROUND: Nonbronchoscopic bronchoalveolar lavage (nBAL) is routinely performed in calves, and airway cytology has great potential in airway disease diagnostics. A good reference framework for nBAL cytology is lacking. OBJECTIVES: To distinguish different cytological profiles in nBAL from grouped housed calves using cluster analysis, and characterize these profiles on individual and herd levels. ANIMALS: Three hundred thirty-eight group-housed calves from 60 herds (mainly dairy and beef ). METHODS: Cross-sectional study. Differential counts of white blood cells were determined on nBAL fluid, followed by differentiation of cytological profiles by K-means-based cluster analysis. These profiles were characterized by reference values, decision tree analysis, and associations with clinical, ultrasonographic, bacteriological, and cytological features. RESULTS: A normal (55.9%), a neutrophilic (41.1%), and an eosinophilic profile (3.0%) were identified. The normal profile was characterized by reference values of 2.3% to 47.4% neutrophils, 35.1% to 95.1% macrophages, 0.4 to 22.9% lymphocytes, and 0.0% to 0.9% eosinophils. The neutrophilic profile was characterized by ≥44.5% neutrophils, <1.6% eosinophils, and <11.5% lymphocytes. This profile was associated with the isolation of Pasteurella multocida, the presence of neutrophils with toxic granulation, and the presence of phagocytosed bacteria in neutrophils. The eosinophilic profile was characterized by eosinophils ≥1.6% (neutrophilia present) or ≥2.4% (neutrophilia absent), and associated with the presence of mast cells. On herd level, the neutrophilic and eosinophilic profiles were present in 85.0% and 15.0% of the herds, respectively. CONCLUSIONS AND CLINICAL IMPORTANCE: This study provides a first step in the development of cytological guidelines, aiding the assessment of airway health and inflammation in calves through nBAL fluid cytology.

Modeling the effects of farming practices on bovine respiratory disease in a multi-batch cattle fattening farm.

Bovine Respiratory Disease (BRD) affects young bulls, causing animal welfare and health concerns as well as economical costs. BRD is caused by an array of viruses and bacteria and also by environmental and abiotic factors. How farming practices influence the spread of these causal pathogens remains unclear. Our goal was to assess the impact of zootechnical practices on the spread of three causal agents of BRD, namely the bovine respiratory syncytial virus (BRSV), Mannheimia haemolytica and Mycoplasma bovis. In that extent, we used an individual based stochastic mechanistic model monitoring risk factors, infectious processes, detection and treatment in a farm possibly featuring several batches simultaneously. The model was calibrated with three sets of parameters relative to each of the three pathogens using data extracted from literature. Separated batches were found to be more effective than a unique large one for reducing the spread of pathogens, especially for BRSV and M.bovis. Moreover, it was found that allocating high risk and low risk individuals into separated batches participated in reducing cumulative incidence, epidemic peaks and antimicrobial usage, especially for M. bovis. Theses findings rise interrogations on the optimal farming practices in order to limit BRD occurrence and pave the way to models featuring coinfections and collective treatments p { line-height: 115%; margin-bottom: 0.25 cm; background: transparent}a:link { color: #000080; text-decoration: underline}a.cjk:link { so-language: zxx}a.ctl:link { solanguage: zxx}.

Effect of on-arrival bovine respiratory disease vaccination on ultrasound-confirmed pneumonia and production parameters in male dairy calves: A randomized clinical trial.

The high degree of commingling and accumulation of stressors during and after transport makes prevention of bovine respiratory disease (BRD) extremely challenging in the veal and dairy beef industry. Upon arrival, vaccination for agents involved in BRD is practically most achievable, but its efficacy under such conditions in dairy veal calves is unknown. Given the high prevalence of subclinical pneumonia in these settings, the primary objective of the present study was to determine the effect of 2 vaccination protocols administered upon arrival against bovine respiratory syncytial virus (BRSV), bovine parainfluenza type 3 virus (BPI-3), and Mannheimia haemolytica on clinical BRD and lung ultrasonographic findings in dairy veal calves. In addition, the effects of vaccination on average daily live weight gain and cold carcass weight were determined. In this randomized clinical trial, 443 male dairy calves were assigned to one of 3 groups: a negative, placebo-controlled group (n = 151), a vaccination group with 2 subcutaneous injections 4 wk apart with an inactivated vaccine containing BRSV, BPI-3, and M. haemolytica (parenteral [PE] group; n = 149) and a second vaccination group receiving an intranasal live-attenuated vaccine containing BRSV and BPI-3 and 2 subcutaneous vaccinations with the same inactivated vaccine as the PE vaccination group (intranasal-parenteral [IN-PE] group; n = 143). Clinical scoring and quick thoracic ultrasonography (qTUS) were performed on all calves on arrival (wk 0), at the peak of respiratory disease (outbreak; wk 1), at the end of the first antimicrobial group treatment (wk 3), and at a long-term evaluation point (wk 10). Culture and nanopore sequencing on nonendoscopic bronchoalveolar lavage (nBAL) samples were used to identify pathogens involved in the outbreak. Upon arrival, 15.1% of the calves had lung consolidation ≥1cm and incidence quickly rose to 42.8% during the outbreak. In both the PE and IN-PE group, the odds of pneumonia in wk 10 were reduced by 62% (odds ratio [OR] = 0.38; 95% confidence interval [CI] = 0.23-0.64) and 41% (OR = 0.59; 95% CI = 0.37-0.96), respectively. Short-term cure rate (50.3%), as determined immediately after the first group antimicrobial treatment, was not influenced by vaccination. In contrast, long-term cure rate, determined at wk 10, was affected by vaccination with higher cure in the PE group compared with the control group (69.4% vs. 51.2%; OR = 2.2; 95% CI = 1.1-5.0). Average daily gain in the first 10 wk of production was not affected by vaccination. Vaccination resulted in an increase in cold carcass weight of 3.5 and 4.3 kg in the PE (95% CI = -0.9-7.9) and IN-PE group (95% CI = -0.17-8.7), respectively. In conclusion, under the conditions of the present study, vaccination upon arrival resulted in a reduced prevalence of pneumonia at wk 10 of production, likely caused both by an improved cure rate of secondary infections and a reduced incidence of new cases between outbreak and long-term evaluation. The present protocol, using qTUS for pneumonia detection and nBAL diagnostics for pathogen identification adds a new dimension to randomized clinical trials on respiratory disease in calves.

Detection of Chlamydia and Chlamydia-like organisms in bovine placental tissue.

This study aimed to investigate the presence of Chlamydia spp. and Parachlamydia acanthamoebae in bovine placental tissue originating from abortion and non-abortion cases in Belgium. Placentas of 164 late term bovine abortions (last trimester of gestation) and 41 non-abortion (collected after calving) cases were analysed by PCR for Chlamydia spp., Chlamydia abortus, C. psittaci and P. acanthamoebae. Additionally, a subset of 101 (75 abortion and 26 non-abortion cases) of these placenta samples were also analysed by histopathology to detect possible Chlamydia-induced lesions. In 5.4% (11/205) of the cases, Chlamydia spp. were detected, and three of those cases were positive for C. psittaci. Parachlamydia acanthamoebae was detected in 36% (75/205) of the cases, being 44% (n = 72) in abortions and 7.3% (n = 3) in non-abortions cases (p < .001). None of the cases was positive for C. abortus. Purulent and/or necrotizing placentitis with or without vasculitis was observed in 18.8% (19/101) of the histopathologically analysed placenta samples. In 5.9% (6/101) of the cases, placentitis was observed along with vasculitis. In the abortion cases, 24% (18/75) of the samples showed purulent and/or necrotizing placentitis, while purulent and/or necrotizing placentitis was visible in 3.9% (1/26) of the non-abortion cases. Placental lesions of inflammation and/or necrosis were present in 44% (15/34) of the cases where P. acanthamoebae was detected, while inflammation and/or necrosis was present in 20.9% (14/67) of the negative cases (p < .05). The detection of Chlamydia spp. and especially P. acanthamoebae, in combination with correlated histological lesions such as purulent and/or necrotizing placentitis and/or vasculitis in placental tissue following abortion, suggests a potential role of this pathogen in cases of bovine abortion in Belgium. Further in-depth studies are necessary to unravel the role of these species as abortifacient agents in cattle and to include them in bovine abortion monitoring programmes.

Detection of Anaplasma phagocytophilum in fetal and placental tissue of bovine abortions and perinatal mortalities.

BACKGROUND: Anaplasma phagocytophilum is a tick-borne zoonotic bacterium that is the aetiologic pathogen of tick-borne fever (TBF) in ruminants. In clinical bovine cases of TBF, abortion and stillbirth may be observed. However, in this regard, the pathophysiology of TBF has not yet been completely elucidated, and no clear guidelines to diagnose A. phagocytophilum-related abortions and perinatal mortalities (APM) are available. METHODS: This exploratory study aimed to investigate the presence of A. phagocytophilum in bovine cases of APM and determine whether placental or fetal spleen tissue has the greatest sensitivity for A. phagocytophilum identification. The placenta and fetal spleen of 150 late-term bovine APM cases were analysed using real-time PCR to detect A. phagocytophilum. RESULTS: A total of 2.7% of sampled placentas were positive for A. phagocytophilum, while none of the fetal spleen samples was. LIMITATIONS: No histopathology to detect associated lesions was performed. Consequently, no evidence of causality between the detection of A. phagocytophilum and APM events could be achieved. CONCLUSION: The detection of A. phagocytophilum suggests a potential role of this pathogen in bovine APM, and placental tissue seems to be the most suitable tissue for its identification.

Hemorrhagic bowel syndrome in dairy cattle: Gross, histological, and microbiological characterization.

Hemorrhagic bowel syndrome (HBS) is a sporadic and fatal disease of predominantly lactating dairy cattle, characterized by segmental hemorrhage and luminal clot formation in the small intestine. Although, Clostridium perfringens and Aspergillus fumigatus have been associated with HBS, the pathogenesis and cause are currently unknown. In this study, 18 naturally occurring cases of HBS (7 necropsied immediately following euthanasia, 11 with 12-48 hour postmortem intervals) were investigated to characterize the pathology and the intestinal microbiome. Hemorrhagic bowel syndrome was characterized by a single small-intestinal, intramucosal hematoma with dissection of the lamina muscularis mucosae. In most cases necropsied immediately after euthanasia (4/7), the intestinal mucosa proximal to the hematoma contained 9 to 14, dispersed, solitary or clustered, erosions or lacerations measuring 4 to 45 mm. In 77% (37/48) of these mucosal lesions, microscopic splitting of the lamina muscularis mucosae comparable to the hematoma was present. These findings suggest the intramucosal hematoma to originate from small mucosal erosions through dissecting hemorrhage within the lamina muscularis mucosae. No invasive fungal growth was observed in any tissue. Bacteriological cultivation and nanopore sequencing showed a polymicrobial population at the hematoma and unaffected intestine, with mostly mild presence of C perfringens at selective culture. Gross and microscopic lesions, as well as the culture and sequencing results, were not in support of involvement of C perfringens or A fumigatus in the pathogenesis of HBS.

Sepsis and survival in critically ill calves: Risk factors and antimicrobial use.

BACKGROUND: Sepsis is a life-threatening disease for which critically important antimicrobials (CIA) frequently are used. Diagnostic and therapeutic guidelines for sepsis and critically ill calves are largely lacking. OBJECTIVES: Identify factors associated with mortality in critically ill calves and describe bacteria obtained from blood cultures of critically ill calves with sepsis and their antimicrobial resistance. ANIMALS: Two-hundred thirty critically ill calves, mainly Belgian Blue beef cattle. METHODS: Retrospective cohort study. Logistic regression, survival analysis, and decision tree analysis were used to determine factors associated with mortality. RESULTS: Of the critically ill calves, 34.3% had sepsis and 61.3% died. The final survival model indicated that calves with sepsis (hazard risk [HR]: 1.6; 95% confidence interval [CI]: 1.0-2.5; P = .05), abnormal behavior (HR: 2.3; 95% CI: 1.3-4.0; P = .005), and hypothermia (HR: 0.82; 95% CI: 0.72-0.95; P = .01) had a significantly higher mortality risk. In a second survival model, hypothermia (HR: 0.87; 95% CI: 0.78-0.96; P = .004) and hypoglycemia (HR: 2.2; 95% CI: 1.5-3.3; P < .001) were risk factors for mortality. Decision tree analysis emphasized the importance of behavior, hypochloremia, hypoglycemia, hyperkalemia, and lung ultrasonography for mortality risk. Escherichia coli (30.6%) was most frequently isolated from blood cultures, of which 90.9% were multidrug resistant. Inappropriate use of antimicrobials was frequent for penicillin, amoxicillin, and sulfamethoxazole/trimethoprim, but less for CIA. CONCLUSIONS AND CLINICAL IMPORTANCE: Many critically ill calves have sepsis, which increases mortality risk. Bacteria involved are often resistant to first-intention antimicrobials but less resistant to CIA. The other identified risk factors for mortality can support therapeutic decision-making.

The in vitro effect of lactose on Clostridium perfringens alpha toxin production and the implications of lactose consumption for in vivo anti-alpha toxin antibody production.

Necro-hemorrhagic enteritis in calves, caused by Clostridium perfringens type A, is a fatal disease, mostly affecting calves in intensive rearing systems. The lack of development of active immunity against α toxin, an essential virulence factor in the pathogenesis, has been proposed as a main trigger. In this experimental study, the effect of a set of milk replacer components on α toxin production, and the effect of lactose on in vivo antibody production, were investigated. For the latter, Holstein-Friesian bull calves (n = 18) were fed an all liquid diet that contained either a milk replacer with high-lactose content (45% DM) or the same milk replacer that was lactase treated, resulting in a lactose-free equivalent. Antibody levels against α toxin were monitored from 2 to 12 wk of age. In the in vitro part of the study, a concentration-dependent inhibitory effect of lactose on in vitro C. perfringens α toxin activity was observed, whereas protein did not influence α toxin activity. The in vivo experiment then showed from the age of 10 wk onwards, that anti-α toxin antibody levels of high-lactose animals declined, whereas antibody levels of the animals consuming lactose-free milk replacer remained the same throughout the trial. This points to a natural decline in maternal immunity of lactose-consuming animals, that is not compensated by the development of an active immunity, resulting in inferior protection. This study suggests that dietary lactose reduces C. perfringens α toxin production in vivo, which may lead to a decreased antigen presentation and thus lower serum antibody levels against the toxin. Consequently, any event causing massive α toxin production puts lactose-consuming calves at higher risk of developing necro-hemorrhagic enteritis.

Dynamics of subclinical pneumonia in male dairy calves in relation to antimicrobial therapy and production outcomes.

Quick thoracic ultrasonography (qTUS) is increasingly used as an on-farm method to diagnose clinical and subclinical pneumonia in dairy calves. The primary objective of this prospective cohort study was to describe dynamics of lung consolidation in a purchase-dependent production system for male dairy calves in relation to antimicrobial therapy and respiratory diagnostics. In addition, we studied the association of cured and uncured pneumonia with average daily gain (ADG) and cold carcass weight (CCW). The third objective was to determine the effects of arriving with lung consolidation on the probability of developing chronic unresponsive pneumonia and reduced performance. A total of 295 male dairy calves were intensively followed by qTUS and clinical scoring on 7 strategic occasions (wk 1, 2, 3, 4, 6, 8, and 12) during the production cycle. Of the calves, 17.6% (52/295) arrived with a lung consolidation ≥1 cm. At the first outbreak of respiratory disease (wk 1 after arrival), this incidence had risen to 30.8%. Initial therapy with tulathromycin and subsequently doxycycline appeared ineffective, resulting in a increase to 43.8% of calves having pneumonia in wk 4. At the start of the first outbreak (wk 1), the majority (86.8%) of the pneumonia cases were subclinical. At wk 4, the outbreak became more clinical, and treatment with amoxicillin resulted in a cure risk of 52.7%. Culture and nanopore sequencing diagnostics on nonendoscopic broncho-alveolar lavage (nBAL) samples identified bovine respiratory syncytial virus and Mycoplasma bovis as the dominant agents in the first outbreak. The isolated M. bovis strain showed mutations associated with macrolide resistance. The second outbreak was characterized by a Pasteurella multocida superinfection and isolation of multiple M. bovis strains from nBAL diagnostic testing. Evaluated over the complete observation period, 83.4% of the calves developed consolidations ≥1 cm on qTUS. Of these calves, 53.9% (135/246) were cured by antimicrobial therapy. Chronic pneumonia (≥30 subsequent days of pneumonia) was seen in 13.9% of the animals (n = 41). Calves with uncured or chronic pneumonia had a lower ADG (992 ± 174 g/d and 930 ± 146 g/d, respectively) compared with calves that never developed pneumonia (ADG = 1,103 ± 156 g/d). In contrast, calves that did fully cure trended toward a lower ADG than calves that never developed pneumonia, but differences were no longer significant. Also, the effect of uncured pneumonia was no longer significant for CCW. Calves with lung consolidation upon arrival had a lower ADG (981 ± 159 g/d vs. 1,045 ± 159 g/d) and were more likely to develop chronic pneumonia [odds ratio = 4.2; 95% confidence interval = 2.1-8.6] compared with calves without consolidation upon arrival. Animals with chronic pneumonia, in turn, had a lower CCW than animals without chronic pneumonia (10.3 ± 4.4 kg; 95% confidence interval: 1.6-19.1 kg). This study documents the consequences of subclinical pneumonia upon arrival and pneumonia developed later in the production cycle on production outcomes in a veal calf setting. Both qTUS and nBAL diagnostics provide important information, offering potential for better control and prevention of bovine respiratory disease in dairy calves.

Epidemiology of Bovine Hemorrhagic Bowel Syndrome in Belgium and The Netherlands.

Hemorrhagic bowel syndrome (HBS) is a poorly understood, sporadic and often fatal disease in cattle. Although, HBS is considered an important disease in dairy cattle, epidemiological data is largely lacking. This study describes the epidemiology of HBS in Belgium and the Netherlands, based on necropsy records from 2009 to 2022, and reports characteristics from 27 cows and 35 dairy operations with HBS, gathered through a survey. The annual incidence of HBS has a significantly increasing trend both at cow and herd level, with incidence above 3.2% in necropsied mature dairy cattle in the most recent years. Estimated herd-level incidence in the Netherlands was double the estimated incidence in Belgium, which might be explained by higher herd size in the Netherlands. Occurrence of HBS was most prevalent in fall, being 40.1% higher than the average of the other seasons. In 35 Flemish (Belgian) surveyed dairy herds with HBS, manifestation of HBS was mostly as solitary cases, and if multiple cases occurred, the time interval was highly variable. In addition, the majority of cows with HBS (61.1%; 16/26) were in more than 100 days lactation. In conclusion, HBS is an important and possibly emerging disease in dairy cattle in Belgium and the Netherlands.

Comparison and optimisation of screening cutoff values for Mycoplasma bovis antibody ELISAs using serum from youngstock.

BACKGROUND: Mycoplasma bovis-associated disease can cause tremendous production losses, welfare issues and high antimicrobial use. Therefore, screening cattle for M. bovis antibodies before entering the herd is a popular and possibly cost-efficient way to reduce disease introduction. However, interpretation of results can be challenging due to variable accuracy between tests and populations. This study's objectives were to compare the diagnostic test accuracy of three commercially available M. bovis antibody ELISAs (ID-screen, Bio K302 and Bio K432) and to explore optimal cutoff values for screening purposes. METHODS: A prospective diagnostic test accuracy study was performed on 170 serum samples from youngstock using Bayesian latent class modelling. Samples were categorised using manufacturer and generated cutoff values. RESULTS: Using the manufacturers' guidelines, ID-screen, Bio K432 and Bio K302 showed 97.6%, 67.4% and 33.6% sensitivity, and 78.8%, 97.6% and 99.1% specificity, respectively. Optimised cutoffs resulted in 94.8%, 82.6% and 78.3% sensitivity, and 94.2%, 92.5% and 79.4% specificity, respectively. CONCLUSIONS: The highest diagnostic accuracy for detecting M. bovis antibodies was obtained by ID-screen (≥110%). However, by adjusting cutoff values, the sensitivity of Bio-X tests could be markedly increased, making these tests also applicable as screening tools. LIMITATIONS: Interpretation needs to be careful as antibodies may be linked to both infectious and non-infectious status.

Cross-sectional study of primary antimicrobial treatment and vaccination coverage in outbreaks of bovine respiratory disease on dairy and beef farms in northern Belgium.

BACKGROUND: To what extent veterinarians active in the dairy or beef sector follow the antimicrobial therapy guidelines made available in different European countries for bovine respiratory disease (BRD) outbreaks, and whether differences in therapeutic or preventive preferences for BRD management exist, is currently unknown. Therefore, the objectives of this cross-sectional study were to compare vaccination coverage and primary antimicrobial and anti-inflammatory treatment on dairy, beef and mixed-breed farms in northern Belgium, and determine their compliance with the recommendations made by the Belgian formulary. METHODS: Information on antimicrobial and anti-inflammatory drug use and vaccination coverage from 190 BRD outbreaks in 180 herds, submitted by 101 veterinarians, was analysed. Multivariable linear probability models, adjusted for clustering at the veterinarian level, were used to determine differences between dairy and beef farms. RESULTS: Antimicrobials and non-steroidal anti-inflammatory drugs (NSAIDs) were used in 93.5% and 81.7% of the BRD outbreaks, respectively. First-line antimicrobials were used as primary treatment in only 42.3%, 50.9% and 38.6% of dairy, beef and mixed-breed farms, respectively. Significant differences (p < 0.05) were observed between dairy and beef farms in terms of use of long-acting macrolides (-17.2 percentage points [pp]; 95% confidence interval [CI]: -31.9, -2.5), steroidal anti-inflammatory drugs (15.2 pp; CI: 0.5, 29.8) and vaccination coverage (bovine respiratory syncytial virus, parainfluenza virus type 3 [33.1 pp; Cl: 15.7-50.6] and Mannheimia haemolytica [23.1 pp; Cl: 3.4-39.8]). LIMITATIONS: The herds that participated in this study were likely among the more motivated regarding BRD control. As such, the information on vaccination coverage is likely not entirely representative of herds in the study area. Interpretation is further complicated by the fact that vaccinated herds were potentially less likely to face a BRD outbreak and therefore participate in the current study. CONCLUSION: This study reveals differences in the primary use of (N)SAIDs, type of antimicrobials used and vaccination coverage on beef and dairy farms in the study region, and also differences in the appropriateness of antimicrobial selection based on the Belgian formulary.

Mandibular Thickness Measurements as Predictive Tool for Specific Dental Disorders in Alpacas (Vicugna Pacos).

Background: Oral health in alpacas is often neglected until severe dental disease becomes evident under the form of a pronounced mandibular swelling with or without fistulation. Mandibular thickness measurements might serve as an easy tool to screen for early increases in thickness thereby identifying alpacas which could benefit from an oral examination. Objective: To study specific risk factors, including age, gender, level of performed measurements and dental disorders, associated with mandibular thickness in alpacas. To determine suitable cutoff values for mandibular thickness at specific locations for the development of a diagnostic test to identify animals with dental disorders. Study design: Cross-sectional study. Methods: Mandibular thickness was measured at standardized locations in 216 alpacas using a Vernier caliper. Risk factors for an increased mandibular thickness were collected through oral examination in sedated animals and by interview of the respective owner. A multivariable linear mixed model was built to identify factors associated with mandibular thickness. Cutoff values for specific dental disorders were obtained after receiver operating characteristics (ROC)-curve analysis. Results: Mandibular thickness was 0.43 ± Standard Error 0.21 mm [95% Confidence interval (CI) = 0.02-0.84 mm] higher at locations where interproximal gum recession was present (P = 0.039). Severe dental disease caused an increase in thickness of 1.90 mm (95% CI= 1.29-2.51 mm) (P < 0.001). Mandibular thickness with a cutoff of 19.4 mm showed a high accuracy for predicting severe dental disease (Se = 0.41; Sp = 0.92). Specifically, thickness at a level perpendicular to the medial canthus of the eye proved a more precise predictor for severe dental disease (AUC, 0.85; 95% CI 0.74-0.96; P < 0.001) with a lower cutoff of 18.5 mm and Sn and Sp of 0.52 and 0.82, respectively. Main limitations: No radiographic or computed tomographic studies were available to support the diagnosis of dental and/or apical disease. Conclusion: Mandibular thickness measurements in alpacas can aid early detection of animals in need of specialized dental care. Most animals with an increased mandibular thickness suffer from advanced dental disease. However, routine dental examinations remain necessary to allow the early detection of dental disorders in alpacas.

Preparing Male Dairy Calves for the Veal and Dairy Beef Industry.

Surplus male dairy calves experience significant health challenges after arrival at the veal and dairy beef facilities. To curb these challenges, the engagement of multiple stakeholders is needed starting with improved care on some dairy farms and better management of transportation. Differing management strategies are also needed if calves arrive at veal and dairy beef facilities under poor condition.