Veterinary diagnostic labs (VDLs) are important service agencies providing essential diagnostic testing for a wide variety of domestic animal species as well as wildlife. They serve key roles in disease monitoring and diagnosis as well as surveillance for diseases of consequence. Of the many roles VDLs serve, one is being a member of the larger team of professionals dealing with the management of the bovine respiratory disease (BRD) complex. VDLs provide a number of services related to the management of BRD. These include disease outbreak investigation, abnormal morbidity characterization, routine monitoring, and biosecurity screening for a variety of infectious agents via methods such as necropsy and histopathology, bacterial culture, antimicrobial sensitivity testing, virus isolation, and serological assays. VDLs continue to look for better methods and assays as instrumentation technology also grows and improves. This is reflected in the growing proliferation of molecular-based assays that provide a high degree of sensitivity and specificity. Professional staff in VDLs work in collaboration with those in academia and private industry to conduct basic research focusing on a different aspect of the BRD complex. VDLs remain a primary source of the varied field-origin infectious agents associated with BRD that are used for research purposes.

Advances in molecular and proteomic technologies and methods have enabled new diagnostic tools for bovine respiratory pathogens that are high-throughput, rapid, and extremely sensitive. Classically, diagnostic testing for these pathogens required culture-based approaches that required days to weeks and highly trained technical staff to conduct. However, new advances such as multiplex hydrolysis probe-based real-time PCR technology have enabled enhanced and rapid detection of bovine respiratory disease (BRD) pathogens in a variety of clinical specimens. These tools provide many advantages and have shown superiority over culture for co-infections/co-detections where multiple pathogens are present. Additionally, the integration of matrix-assisted laser desorption ionization time of flight mass spectrometry (MS) into veterinary diagnostic labs has revolutionized the ability to rapidly identify bacterial pathogens associated with BRD. Recent applications of this technology include the ability to type these opportunistic pathogens to the sub-species level (specifically Mannheimia haemolytica) using MS-based biomarkers, to allow for the identification of bacterial genotypes associated with BRD versus genotypes that are more likely to be commensal in nature.

Increased antimicrobial resistance in bovine respiratory bacterial pathogens poses a threat to the effective control and prevention of bovine respiratory disease (BRD). As part of continued efforts to develop antimicrobial alternatives to mitigate BRD, the microbial community residing within the respiratory tract of feedlot cattle has been increasingly studied using next-generation sequencing technologies. The mucosal surfaces of upper and lower respiratory tracts of cattle are colonized by a diverse and dynamic microbiota encompassing commensal, symbiotic, and pathogenic bacteria. While a direct causal relationship between respiratory microbiota and the development of BRD in feedlot cattle has not been fully elucidated, increasing evidence suggests that the microbiota contributes to respiratory health by providing colonization resistance against pathogens and maintaining homeostasis. Certain management practices such as weaning, transportation, feed transition, and antibiotic application can disrupt the respiratory microbiota, potentially altering pathogen colonization. Microbiota-based approaches, including bacterial therapeutics that target restoring the normal respiratory microbiota, may provide new methods for mitigating BRD in feedlot cattle in place of antibiotics. In addition, the distinct bacterial respiratory microbial communities observed in BRD-affected and healthy feedlot cattle may allow for future application of microbiota-based techniques used in the diagnosis of BRD.

Bovine respiratory disease (BRD) treatment failure occurs when animals receiving a treatment regimen for BRD fail to directly return to health, resulting in chronic illness and a requirement for repeated treatments, sale for salvage slaughter, euthanasia or death. BRD treatment failure has both direct and indirect impacts. Direct impacts include costs to manage chronically ill animals, including those associated with BRD relapse treatment; reduced returns from animals sent for salvage slaughter, loss of the initial investment to purchase the animal and feed and other accumulated expenses to death, and costs associated with carcass disposal. Indirect impacts include costs of infrastructure requirements, and negative effects on animal welfare and employee morale.

In cattle treated for respiratory disease, resolution of clinical signs has been the mainstay of determining treatment response and treatment efficacy. Through the use of calf lung ultrasound, we have found that pneumonia can persist or recur in the face of antibiotic therapy, despite improved clinical signs, leading to greater risk of clinical disease and more antibiotic use in the future. This review will discuss the pros and cons of using clinical signs to define resolution of disease and discuss how to implement lung ultrasound to improve our ability to accurately measure the impact of antibiotic therapy in cattle with respiratory disease.

Bovine respiratory disease (BRD) is one of the most common indications for antimicrobial therapy in beef cattle production and research trials demonstrate that antibiotic therapy greatly improves clinical outcome for BRD. These trials also show that BRD treatment success rates are less than 100% and that there are opportunities to optimize antimicrobial prescribing and improve clinical outcomes if the underlying cause(s) of BRD treatment failures can be identified and addressed. As the etiology of BRD in an individual animal is frequently multi-factorial in nature; it is likely that BRD treatment failures also result from complex interactions between the drug, drug administrator, animal host, pathogens, and the environment. This review will focus specifically on the pharmacological aspects, specifically the interactions between the host and the drug and the drug and the drug administrator, of BRD treatment failures and the actions that veterinary practitioners can take to investigate and mitigate therapeutic failures in future cases.

Genomic variation exists in cattle that affects their susceptibility to the complex of pathogens responsible for bovine respiratory disease (BRD). Heritability estimates and genome-wide association analyses (GWAA) support the role of host genomic variation in BRD susceptibility. Heritability estimates for BRD susceptibility range from 0.02 to 0.29 depending on the population, the definition of the disease, and the accuracy of diagnosis. GWAA have identified genomic regions (loci) associated with BRD in beef and dairy cattle based on a variety of BRD diagnostic criteria. National standards need to be developed for BRD diagnostics and reporting to facilitate selection. Commercial genotyping is available to predict BRD susceptibility in dairy cattle and for the selection of replacement animals. Disease pathogen profiles vary by region and can result in genetic heterogeneity where different loci are important for susceptibility to different BRD pathogens. Although the identification of the BRD pathogens may not be critical for treatment, it is of paramount importance in identifying loci that render cattle susceptible to the disease. Identification of loci associated with host susceptibility to BRD provides a foundation for genomic selection to reduce disease and opens the possibilities to a better understanding of how the host defends itself.

Bovine respiratory disease (BRD) is of considerable economic importance to the dairy industry, specifically among young animals. Several studies have demonstrated that BRD has a significant genetic component, with heritabilities ranging from 0.04 up to 0.22, which could be utilized to select more resistant animals. Taking advantage of available genomic data will allow more accurate genetic predictions to be made earlier in an animal's life. The availability of genomic data does not negate the necessity of quality phenotypes, in this case, records of BRD incidence. Evidence has shown that genetic selection is possible through the use of producer-recorded health information. The national dairy cooperator database currently has minimal records on respiratory problems. There is an existing pipeline for these data to flow from events recorded by producers on the farm to the national database used for genetic evaluation. Additional data could also be collected through the expansion of currently utilized termination codes and used in conjunction with the records of direct health events. Selection for animals with improved BRD resistance is possible at the national level; however, collection of additional phenotypes remains a significant hurdle.

Bovine respiratory disease (BRD) is an important disease in dairy calves due to its long-lasting effects. Early identification results in better outcomes for the animal, but producers struggle to identify all calves with BRD. Sickness behavior, or the behavioral changes that accompany illness, has been investigated for its usefulness as a disease detection tool. Behavioral changes associated with BRD include decreased milk intake and drinking speed, depressed attitude, and less likelihood of approaching a novel object or stationary human. Behavioral measurements are useful, as they can be collected automatically or with little financial input. However, one limitation of many BRD behavioral studies includes the use of either lung auscultation or clinical signs as reference methods, which are imperfect. Additionally, external factors may influence the expression of sickness behavior, which can affect if and when behavior can be used to identify calves with BRD. Behavioral measures available to detect BRD lack adequate sensitivity and specificity to be the sole means of disease detection, especially when detection tools, such as calf lung ultrasound, have better test characteristics. However, using behavioral assessments in addition to other detection methods can allow for a robust BRD detection program that can ameliorate the consequences of BRD.

Assessment of behavior is a longstanding strategy to assist the diagnosis of clinical bovine respiratory disease (BRD) in beef cattle. Cattle with systemic inflammation caused by infectious pathogen(s) display predictable behavioral adaptations compared to healthy cohorts. Behavioral alterations in BRD-affected cattle include lethargy, social isolation, and anorexia. However, behavior assessment to support BRD case definition in the production setting is challenging because: (1) other bovine diseases cause behavior alterations similar to BRD; (2) cattle have inherent prey instinct to disguise sickness behavior during human evaluation; (3) labor constraints dictate very brief observation of animal behavior; and (4) traditional behavior assessment is subjective and agreement is often poor. Some of these challenges may be overcome with the use of advanced technologies that allow continuous, remote, and objective behavior assessment of individual cattle. Automated methodologies for behavior assessment include three-axis accelerometers that quantify physical behaviors, systems that document feeding/watering behavior, and triangulation systems that document spatial behavior. Each of these behavior-monitoring approaches generates unique information and may facilitate early detection of BRD compared to traditional methods. Nevertheless, adoption of behavior assessment technologies for BRD diagnosis in beef operations hinges upon improved detection, positive return on investment, and successful integration within existing BRD management practices.

Bovine respiratory disease (BRD) is the most common cause of morbidity and mortality in North American beef cattle. In recent years, isolation of strains of Mannheimia haemolytica that are resistant to multiple different classes of antimicrobials has become commonplace. New research would suggest that the routine use of antimicrobials by some cattle operations might be driving emerging resistance patterns, with the majority of the spread observed due to propagation of strains of M. haemolytica that have acquired integrative conjugative elements. To date, there is little information evaluating the impact of antimicrobial resistance on clinical outcome in cattle with BRD.