The primary objective of this study was to determine associations between ultrasound-based classification systems (using maximum consolidations depth, number of quadrants with consolidation, and consolidation location), clinical indicators, and performance outcomes (ultrasonographic cure, ADG, and cold carcass weight [CCW]) in veal calves following oral metaphylaxis. A retrospective cohort study was conducted on 1,090 white veal calves originating from 3 Belgian veal herds. Clinical scoring and quick thoracic ultrasound (qTUS) follow-up were done by 4 experienced operators at arrival (wk 0), at the start of the first metaphylactic treatment with doxycycline (treatment initiation, wk 1), at the end of this metaphylactic treatment (short-term evaluation, wk 3) and on a long-term evaluation point (wk 10-12). Cure was defined as complete reaeration of previously consolidated lung tissue. Pathogens were identified using culture and nanopore sequencing. One week after arrival, healthy lungs (no consolidation), mild pneumonia (consolidation <1 cm), moderate pneumonia (consolidation ≥1 but <3 cm), and severe pneumonia (consolidation ≥3 cm) were identified in 46.9%, 12.4%, 21.4%, and 19.4% of calves, respectively. Short-term cure was 59.3% for calves with mild pneumonia, 50.2% for calves with moderate pneumonia, and 32.7% for calves with severe pneumonia, resulting in a total short-term cure of 45.9%. Coronavirus, respiratory syncytial virus, influenza D virus, and Mycoplasmopsis bovis were circulating during treatment. At the long-term evaluation point (wk 10-12), final cure was 59.3%, 55.8%, and 40.3% for calves with mild, moderate, and severe pneumonia at treatment initiation, respectively. Multivariable regression models indicated that different interactions between qTUS categories and number of affected quadrants were associated with short- and long-term odds of cure. Generated models resulted in 3 classification methods, either based on maximum consolidation depth, number of affected quadrants, or an integrated system of both. Calves with clinical pneumonia (Wisconsin score ≥5 and lung consolidation ≥1 cm) had decreased short-term odds to be cured after metaphylaxis compared with calves with subclinical pneumonia (Wisconsin score <5 and lung consolidation ≥1 cm; odds ratio = 0.43; 95% CI: 0.27-0.67). For calves with severe pneumonia in wk 10-12, when compared with calves in a lower qTUS category, ADG and CCW were reduced by 104 g/d (SD = 13; 95% CI: 78-130) and 7.1 kg (SD = 1.9; 95% CI: 3.4-10.9), respectively. Categorization based on maximum consolidation depth, the number of affected quadrants, or an integrated system of both has the potential to be included in an ultrasound scoring system. However, based on the practicality for recording, reporting, and follow-up, the authors recommend categorizing calves into mild, moderate, and severe pneumonia based on maximum consolidation depth measurement, referred to as qTUS score, as a practical classification system for ultrasonographic lung assessment in calves.

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 (NC) (n = 151), a vaccination group with 2 subcutaneous injections 4 weeks 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 non-endoscopic broncho-alveolar 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). ADG in the first 10 weeks 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.

Background: The depth of lung consolidation (≥ 1 and ≥ 3 cm) on thoracic ultrasonography (TUS) is increasingly used as a criterion for antimicrobial treatment. However, its association with bacterial infections remains unclear. Objectives: To investigate the associations of clinical and ultrasonographic findings, particularly consolidation depth, with opportunistic bacterial infections (OBI), viral infections, or Mycoplasma bovis (also known as Mycoplasmopsis bovis) infections. Different definitions of OBI were explored, based on various combinations of bacterial species, with or without a neutrophilic profile on cytology. Animals: Eighty-six group-housed calves with at least one clinical sign of respiratory disease from 19 herds experiencing a respiratory epidemic. Methods: Cross-sectional study. A physical examination, TUS, and non-bronchoscopic bronchoalveolar lavage were performed. The definitions of OBI were based on semi-quantitative culture results and cytology. Results: Calves with consolidations of ≥ 0.5 cm had higher odds of having an OBI considering most definitions, on M. bovis isolation (odds ratio [OR] = 57.3; 95% confidence interval [CI] = 1.5–2300; p = 0.03) and isolation of a bacterial agent in general (OR = 15.5; 95% CI = 2.3–100; p = 0.01). Animals with consolidation ≥ 1 cm had higher odds of OBI considering all definitions, virus isolation (OR = 15.6; 95% CI = 1.0–240; p = 0.05) and isolation of a bacterial agent in general (OR = 6.9; 95% CI = 1.7–28; p = 0.01). Consolidation ≥ 3 cm, cough, and the California score were not significantly associated with OBI, M. bovis, or both. Conclusion: In herds experiencing a respiratory epidemic, consolidation depths ≥ 0.5 and ≥ 1 cm might indicate respiratory disease with a bacterial component.

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.

Early recognition and rapid appropriate antimicrobial treatment is essential for survival of sepsis. To date, it is unclear which sepsis score should be used for an early diagnosis in calves. The objective of this study was to evaluate two existing scores (Trefz and Fecteau), three novel calf sepsis screening models (CSS, CSS_A, CSS_B), and blood culture as diagnostic test for sepsis, using Bayesian latent class evaluation. A total of 131 sick calves were included in this study. Sepsis prevalence was 45%, 27%, 56%, 47%, and 55%, when using the Trefz score, Fecteau score, CSS, CSS_A, and CSS_B, respectively, and 22% had a relevant positive blood culture. The newly established models CSS (including ≥2 SIRS-criteria and abnormal mental state) and CSS_B (alternative model CSS for practice, substituting abnormal leukocyte count with mucosae) had the highest sensitivity, with 86% and 84%, respectively, and could be interesting screening tests for sepsis. Sensitivity of the existing Trefz and Fecteau score was 70% and 35–39%, respectively. The presented new sepsis scoring systems have potential as screening tests to identify calves at risk, after which a calf-side diagnostic test is advised to confirm the diagnosis. Its use might aid in the rationalization of antimicrobial use in critically ill calves.