Shipping Fever (BRD)

Shipping fever, more accurately known as bovine respiratory disease (BRD) or bovine respiratory disease complex, represents the most economically significant health problem facing the cattle industry worldwide. This multifactorial disease syndrome develops when stress factors, particularly those associated with transportation, weaning, and commingling, compromise the immune system and allow viral and bacterial pathogens to cause severe respiratory infection. The term "shipping fever" derives from the historical observation that cattle frequently developed respiratory disease within days to weeks of transportation, though modern understanding recognizes that stress from multiple sources beyond transport contributes to disease development. BRD causes tremendous economic losses through mortality, treatment costs, reduced performance, and chronic lung damage affecting lifetime productivity.

Shipping fever affects cattle operations globally wherever cattle are transported, marketed through auction facilities, or managed in intensive systems that involve animal movement and mixing. The condition is particularly prevalent in the North American beef cattle industry, where the production system typically involves multiple ownership transfers, transportation over long distances, and commingling of calves from numerous sources at feedlots. Studies estimate that BRD affects 15-45 percent of feedlot cattle, with some populations experiencing even higher morbidity rates during high-risk periods. Dairy cattle are also affected, particularly heifers transported to custom raising facilities or bulls moved for breeding purposes. The disease occurs year-round but shows seasonal peaks corresponding to periods of greatest cattle movement and environmental stress.

The economic impact of shipping fever is staggering, with annual losses in North America alone estimated at over one billion dollars when mortality, morbidity, treatment costs, and performance losses are considered. Direct mortality from BRD ranges from 1-5 percent in most feedlots but can exceed 10 percent in high-risk populations or during severe outbreaks. Treatment costs including antimicrobials, anti-inflammatories, and labor accumulate rapidly during outbreaks. Reduced feed intake during illness impairs growth and feed efficiency, extending time to market. Chronic lung damage in recovered animals causes permanent performance reduction, with affected cattle showing 10-20 percent lower average daily gains than healthy counterparts. Carcass quality and value may be reduced due to lung lesions detected at slaughter. The welfare impact on affected animals represents an additional cost that is difficult to quantify but ethically significant.

Understanding shipping fever as a multifactorial disease rather than a simple infection is essential for developing effective prevention and treatment strategies. The interaction of stress factors, viral infections, bacterial pathogens, and individual animal susceptibility creates a complex disease syndrome that cannot be addressed through any single intervention. Prevention requires attention to management practices, vaccination programs, and environmental factors, while treatment must be timely and appropriate to prevent progression to severe or chronic disease. Working with licensed veterinarians to develop comprehensive BRD prevention and control programs represents the most effective approach to reducing losses from this devastating condition.

Shipping fever results from the complex interaction of stress factors, viral pathogens, and bacterial pathogens that together overwhelm respiratory defenses and cause clinical disease. The bacterial agents most commonly involved include Mannheimia haemolytica (formerly Pasteurella haemolytica), Pasteurella multocida, Histophilus somni (formerly Haemophilus somnus), and Mycoplasma bovis. These bacteria are normal inhabitants of the upper respiratory tract in healthy cattle but become pathogenic when respiratory defenses are compromised. Mannheimia haemolytica is the most frequently isolated and most virulent bacterial pathogen, producing a potent leukotoxin that destroys immune cells and causes severe tissue damage. Viral agents that predispose to bacterial invasion include bovine respiratory syncytial virus (BRSV), parainfluenza-3 virus (PI3), infectious bovine rhinotracheitis virus (IBR/BHV-1), and bovine viral diarrhea virus (BVDV).

While no direct genetic predisposition to shipping fever has been definitively established, substantial individual variation in disease susceptibility exists that likely has genetic components. Bos indicus cattle breeds, including Brahman and their crosses, appear somewhat more resistant to BRD than British and Continental Bos taurus breeds, possibly due to differences in immune function, stress response, or adaptation to environmental challenges. Within any breed, individual animals show marked variation in disease resistance, with some cattle remaining healthy despite heavy exposure while others succumb to severe disease with minimal apparent challenge. This individual variation suggests genetic factors influencing immune competence, stress tolerance, and other relevant traits. Selection for BRD resistance is complicated by the difficulty of measuring resistance in commercial populations and the interaction of genetics with environment and management.

Environmental and management stress factors are the critical trigger converting normal respiratory flora into pathogenic invaders. Transportation stress is the primary risk factor, with duration, distance, handling quality, vehicle conditions, temperature extremes, and feed and water deprivation all contributing to immune suppression. Weaning stress disrupts the calf both nutritionally and psychologically through separation from the dam. Commingling stress exposes animals to new social hierarchies, novel pathogens, and often fighting and competition for resources. Marketing stress combines handling, unfamiliar environments, feed and water disruption, and exposure to pathogens from multiple sources. Environmental stress from temperature extremes, temperature fluctuation, high humidity, dust, and poor ventilation adds additional immune burden. The cumulative effect of multiple stressors is greater than any individual factor alone.

Risk factors for shipping fever are well characterized, allowing identification of high-risk animals and situations for targeted intervention. The highest-risk cattle are lightweight calves (under 300 pounds) sourced from multiple origins, transported long distances, and commingled at feedlots or backgrounding operations. The 14-28 day period following arrival at a new facility represents peak risk for disease development. Calves that have not been weaned before shipment (hot or fresh calves) face higher risk than preconditioned calves weaned 30-45 days before sale. Cattle purchased through auction markets have higher BRD rates than those purchased directly from ranches. Poor body condition at arrival indicates prior stress or nutritional inadequacy that increases susceptibility. Concurrent illness including parasitism, pinkeye, or other infections compromises immune resources.

The pathophysiology of shipping fever begins with stress-induced immune suppression followed by viral infection and ultimately bacterial invasion of the lower respiratory tract. Stress hormones including cortisol suppress multiple aspects of immune function, particularly affecting cells of the innate immune system that provide first-line respiratory defense. Viral infection damages the respiratory epithelium, impairing the mucociliary clearance mechanism that normally removes inhaled particles and pathogens. Viral infection also directly suppresses immune cell function and induces inflammatory changes that alter the lower respiratory tract environment. With defenses compromised, bacteria from the upper respiratory tract descend into the lungs and establish infection. Mannheimia haemolytica produces leukotoxin that destroys neutrophils and alveolar macrophages, releasing destructive enzymes and inflammatory mediators that cause tissue damage. The resulting consolidation replaces functional lung tissue with inflammatory debris, progressively impairing oxygen exchange.

Early warning signs of shipping fever are subtle and require vigilant observation to detect before disease progresses to obvious clinical illness. The earliest indicators often include mild depression with decreased alertness and reduced interest in surroundings. Affected cattle may separate slightly from the group or lag behind when the pen is moved to feed or water. Feed intake decreases, with affected animals showing less enthusiasm at feeding time or eating more slowly than penmates. A subtle increase in respiratory rate or mild respiratory effort may be detectable with careful observation. Body temperature may be mildly elevated (102-103°F) before other signs are apparent. Mild, clear nasal discharge might be present. Recognizing these early signs provides the critical window for treatment intervention before extensive lung damage occurs.

As shipping fever progresses, clinical signs become increasingly obvious and severe. Fever typically rises to 104-107°F (40-41.7°C) in acute cases, though temperature may be lower in chronic or immunocompromised animals. Depression becomes pronounced, with affected cattle showing dull expression, drooping ears, and reluctance to move. Respiratory rate increases significantly, often to 50-70 breaths per minute or higher. Breathing becomes labored, with increased abdominal effort as cattle struggle to move air through compromised lungs. Nasal discharge progresses from clear and serous to thick, yellow or green mucopurulent material. Coughing develops, ranging from occasional soft coughs to frequent harsh productive coughing. Animals may stand with elbows abducted and neck extended to facilitate airflow.

Behavioral changes in cattle with shipping fever reflect both systemic illness and respiratory distress affecting normal activities. Affected cattle isolate themselves from penmates, standing alone at the periphery of the pen or in corners. They cease social interactions and show no interest in the activities of neighboring cattle. Feed intake drops dramatically, with cattle making occasional approaches to the bunk but eating little. Water consumption also decreases. Rumination activity declines or stops as systemic illness suppresses normal digestive function. Movement becomes reluctant, with affected cattle resisting being driven and lagging behind when pens are moved. Cattle may prefer standing to lying down if breathing is easier in the standing position. Overall activity levels decline markedly as disease progresses.

Physical examination findings in cattle with shipping fever provide diagnostic confirmation and help assess disease severity. Temperature measurement reveals the fever characteristic of active bacterial infection, though some chronic or severely compromised cattle may be hypothermic. Auscultation of the lungs identifies abnormal breath sounds including harsh bronchial sounds, crackles, and wheezes, with areas of consolidation showing decreased or absent normal sounds. The distribution of lung involvement often favors the cranioventral lung fields in bacterial pneumonia. Nasal discharge should be characterized as serous, mucopurulent, or purulent, with blood-tinged discharge suggesting severe lung damage. Assessment of hydration status through skin tent, eye position, and mucous membrane moisture guides supportive care decisions. Pain response on chest wall palpation may be present if pleuritis has developed.

Symptom progression in untreated shipping fever typically follows a concerning trajectory over 3-7 days from early signs to severe disease or death. The mild depression and decreased appetite of early disease progress within 24-48 hours to obvious illness with high fever and respiratory distress. Without treatment, respiratory function deteriorates progressively as consolidation extends to involve larger portions of the lungs. Some cattle develop pleuritis (inflammation of the pleural membranes), adding severe chest pain to their respiratory compromise. Weight loss becomes apparent as feed intake remains depressed and catabolism increases. A portion of cattle progress to fatal illness within 5-10 days, while others survive the acute phase but develop chronic pneumonia with persistent lung damage affecting lifetime performance.

Emergency symptoms requiring immediate intervention include severe respiratory distress with open-mouth breathing, cyanosis (blue or purple mucous membranes), collapse or recumbency, temperatures exceeding 106°F (41.1°C), and bloody nasal discharge indicating severe lung damage. Cattle showing extreme neck extension with elbows abducted and obvious dyspnea face immediate risk of respiratory failure. Sudden death can occur with peracute disease, particularly in cattle infected with highly virulent Mannheimia haemolytica strains. Any rapid deterioration from mild to severe illness suggests aggressive disease requiring immediate aggressive intervention. The presence of multiple severely affected cattle in a group indicates an outbreak situation requiring both individual treatment and population-level response.

Clinical examination forms the foundation of shipping fever diagnosis, with the combination of history, signalment, and physical findings typically sufficient to establish a working diagnosis and initiate treatment. The history should address transportation details, time since arrival, source and mixing history, vaccination status, and any previous illness or treatment. Visual assessment notes respiratory rate and effort, nasal discharge, depression, body condition, and any separation from the group. Physical examination measures rectal temperature and includes thorough auscultation of all lung fields, evaluating breath sound quality and identifying areas of consolidation or abnormal sounds. The combination of recent transport or stress, fever, respiratory signs, and abnormal lung sounds provides strong support for BRD diagnosis. Clinical assessment using scoring systems helps standardize evaluation and treatment decisions.

Diagnostic testing extends clinical examination to identify specific pathogens, guide treatment selection, and support herd health decisions. Deep nasopharyngeal swabs or transtracheal wash samples can be cultured to identify bacterial pathogens and determine antimicrobial susceptibility patterns. PCR testing provides rapid, specific identification of viral and bacterial agents. Serological testing detects antibodies to specific respiratory pathogens, though acute and convalescent paired samples are needed to demonstrate rising titers indicating active infection. Complete blood counts show patterns consistent with bacterial infection, including elevated white blood cell counts with a neutrophilia and left shift. Thoracic ultrasound allows visualization of lung consolidation and provides prognostic information, with greater consolidation correlating with poorer outcomes. Radiography offers detailed lung imaging but is impractical for field use with cattle.

Differential diagnosis for cattle presenting with respiratory disease must consider conditions other than classic shipping fever that may require different approaches. Interstitial pneumonia from acute bovine pulmonary emphysema and edema (ABPEE or fog fever) causes severe respiratory distress but typically occurs in cattle on lush pasture rather than recently transported cattle. Aspiration pneumonia following drenching accidents presents with respiratory signs but has characteristic history. Lungworm infection (Dictyocaulus viviparus) causes coughing and respiratory difficulty in grazing cattle. Upper respiratory disease including IBR with primary upper tract involvement may initially resemble BRD. Cardiac disease can cause increased respiratory rate and exercise intolerance. Anaplasmosis and other systemic infections may present with fever and depression. Thorough clinical evaluation distinguishes these conditions.

Herd-level diagnostics address outbreak situations and support development of effective prevention programs. Postmortem examination of fatal cases provides definitive diagnosis through characteristic gross and microscopic lung lesions and allows sample collection for pathogen identification and susceptibility testing. Lung lesion scoring at slaughter provides population-level data on BRD impact, including subclinical disease not detected through clinical observation. Serological surveys characterize viral pathogen exposure in populations. Risk factor analysis examines associations between animal characteristics, management factors, and disease occurrence. Antimicrobial susceptibility monitoring identifies resistance patterns guiding treatment selection. This systematic investigation guides both immediate outbreak management and longer-term prevention program development.

Emergency treatment for shipping fever requires immediate initiation of antimicrobial therapy and supportive care when cattle are identified with moderate to severe respiratory disease. The critical importance of early treatment cannot be overemphasized, as studies consistently show that treatment within 12-24 hours of onset dramatically improves outcomes compared to delayed treatment. Severely affected cattle should be quietly moved to a hospital pen with easy access to feed and water. Broad-spectrum antimicrobial therapy targeting respiratory pathogens should begin immediately based on clinical diagnosis without waiting for diagnostic results. Non-steroidal anti-inflammatory drugs provide fever reduction, anti-inflammatory effects that may limit lung damage, and analgesia improving animal comfort. Cattle too sick to rise or showing cyanosis require immediate assessment of prognosis and humane endpoints.

Medical management of shipping fever relies primarily on antimicrobial therapy targeting the bacterial pathogens involved in BRD. Multiple antimicrobial classes demonstrate efficacy against respiratory pathogens, including macrolides (tilmicosin, tulathromycin, gamithromycin, tildipirosin), tetracyclines (oxytetracycline), amphenicols (florfenicol), fluoroquinolones (enrofloxacin, danofloxacin), and cephalosporins (ceftiofur). Long-acting formulations that maintain therapeutic levels for 3-7 days reduce handling stress and improve compliance. Drug selection should be based on known susceptibility patterns, withdrawal time requirements, cost considerations, and veterinary guidance. Treatment failure rates of 10-20 percent are typical even with appropriate first treatment, and retreatment with an antimicrobial from a different class is indicated for non-responders. All treatments must comply with withdrawal time requirements for food-producing animals.

Surgical intervention has no role in routine shipping fever treatment, as the diffuse nature of lung involvement precludes surgical approaches. The rare exception might involve drainage of localized abscesses that develop as a complication of pneumonia, though this is uncommon and typically impractical. Tracheostomy might theoretically be considered for cattle with upper airway obstruction, but this would not address the primary lung pathology of BRD. The focus of intervention remains medical management with antimicrobials and supportive care. Veterinary expertise should be directed toward appropriate drug selection, adequate supportive care, and decisions about prognosis and humane endpoints for severely affected cattle.

Supportive care complements antimicrobial therapy and may influence outcomes, particularly for moderately to severely affected cattle. Maintaining hydration through provision of easily accessible fresh water or parenteral fluid therapy in severe cases supports cardiovascular function and drug distribution. Minimizing stress through quiet handling, avoiding unnecessary movement, and providing comfortable housing allows energy to be directed toward healing. Nutritional support through provision of palatable hay and appropriate feeds maintains some nutrient intake during illness. Separation from healthy penmates in a hospital pen reduces transmission while allowing closer monitoring and individual care. Temperature regulation through shelter from extreme heat or cold reduces metabolic demands on compromised animals.

Metaphylactic treatment protocols address high-risk populations through antimicrobial administration to all animals in a group at or near arrival, before clinical disease develops. This approach recognizes that a proportion of cattle in high-risk groups will develop BRD regardless of observation-based pull and treat programs, and that treatment before clinical disease produces better outcomes than waiting for illness. Metaphylaxis is typically applied to cattle meeting high-risk criteria including commingled lightweight calves from multiple sources, cattle with unknown vaccination history, and cattle from auction markets. The timing of metaphylaxis relative to arrival affects efficacy, with most programs treating within 24-48 hours of arrival. Economic analysis generally supports metaphylaxis in high-risk populations despite treatment costs because of reduced morbidity, mortality, and performance losses.

Treatment decision factors balance animal welfare, economic considerations, and antimicrobial stewardship responsibilities. Early-stage cases with moderate symptoms warrant aggressive treatment given good response rates and favorable cost-benefit ratios. Severe cases with extensive lung involvement, prolonged illness, or failure to respond to multiple treatment attempts present difficult decisions, as prognosis worsens significantly with disease progression and treatment failure. Economic analysis comparing treatment costs to animal value and expected performance influences decisions in commercial feedlots. Chronic cases with permanent lung damage may be better served by early marketing rather than continued feeding as chronic poor performers. Antimicrobial stewardship requires judicious use of these valuable drugs, appropriate drug selection, and avoiding unnecessary treatment of low-risk cattle. Veterinary consultation ensures appropriate treatment decisions balancing these competing factors.

Recovery timelines for shipping fever vary considerably based on disease severity at treatment initiation, treatment appropriateness, and individual animal factors. Cattle with mild disease treated promptly often show significant improvement within 24-48 hours, with temperature normalization and improved attitude being early indicators of response. However, resolution of lung consolidation and return to full respiratory function requires considerably longer, typically 2-4 weeks for moderate cases. Severe cases that survive may require extended recovery periods of 4-8 weeks or longer and frequently suffer permanent lung damage affecting lifetime performance. Treatment failure rates of 10-20 percent even with appropriate first treatment reflect the challenges of addressing established lung damage.

Post-treatment care and monitoring focus on detecting relapse, assessing recovery progress, and supporting return to normal performance. Treated cattle should be monitored daily for at least 7-10 days following treatment, watching for return of fever, respiratory signs, or depression indicating treatment failure or relapse. Temperature monitoring of treated cattle helps objectively assess response. Cattle not showing expected improvement within 48-72 hours may need retreatment with a different antimicrobial class. Recovery housing should provide comfortable conditions with easy access to feed and water. Gradual return to normal pen conditions and activities allows assessment of exercise tolerance and respiratory compromise. Record keeping of individual treatment responses supports future management decisions.

Prognosis for shipping fever depends heavily on disease severity at treatment initiation and treatment timing. Cattle with mild to moderate disease treated within 24-48 hours of symptom onset generally have good prognosis for survival and acceptable recovery of function. Studies show first-treatment success rates of 75-90 percent when treatment is initiated early with appropriate drugs. Prognosis worsens significantly with treatment delay, with each 24-hour delay reducing expected recovery rates. Severe cases with extensive lung consolidation, high fever, and pronounced respiratory distress have guarded prognosis even with aggressive treatment. Cattle requiring multiple treatments have worse long-term performance outcomes than those responding to first treatment. The specific pathogens involved influence prognosis, with Mycoplasma bovis involvement predicting poorer outcomes.

Return to production considerations address the long-term implications of BRD for cattle performance and value. Cattle recovered from shipping fever typically show reduced average daily gain, poorer feed efficiency, and longer time to market compared to cattle that remained healthy. Studies suggest performance reductions of 0.1-0.2 pounds per day average daily gain in cattle treated once, with greater reductions in cattle requiring multiple treatments. Lung damage detected at slaughter through consolidation and adhesions may result in carcass trim and value reduction. The economic impact of these performance losses should be considered in management decisions. Some operations find that early marketing of chronic poor performers makes more economic sense than continued feeding to heavier weights. Recovered cattle can continue to normal slaughter when fit, with appropriate observation of any drug withdrawal requirements.

Vaccination protocols form a cornerstone of shipping fever prevention, though vaccines must be part of comprehensive programs addressing management factors. Respiratory vaccines targeting viral pathogens (IBR, BVD, PI3, BRSV) are widely used, with both modified-live and killed products available. Bacterial vaccines targeting Mannheimia haemolytica, Pasteurella multocida, and Histophilus somni are also available, with various antigen preparations. Vaccination timing is critical, as protective immunity requires 2-3 weeks to develop. Pre-weaning vaccination allows immunity development before weaning stress compromises immune response. Boosters at or before shipment reinforce immunity. Arrival vaccination at feedlots provides some benefit but cannot produce immunity quickly enough to prevent early BRD cases. Vaccine selection and protocols should be developed with veterinary guidance based on operation-specific risk factors and pathogen exposure patterns.

Preconditioning programs represent one of the most effective strategies for reducing shipping fever risk in cattle destined for feedlot entry. These programs typically include weaning calves at least 30-45 days before sale, vaccination with respiratory vaccines during the preweaning period, training calves to eat from bunks and drink from waterers, and often castration and dehorning. Preconditioned calves experience dramatically lower BRD rates than calves shipped immediately after weaning, with studies showing 50 percent or greater reduction in morbidity. The benefits of preconditioning extend to improved growth performance and reduced treatment costs that generally offset the costs of the preconditioning program. Market premiums for preconditioned calves have developed in recognition of their health and performance advantages.

Biosecurity measures and source selection reduce pathogen exposure and transmission pressure contributing to BRD. Sourcing cattle directly from ranches rather than through auction markets reduces exposure to pathogens from multiple sources. Single-source loads from individual ranches have lower BRD rates than commingled loads. Limiting the number of source locations for incoming cattle reduces pathogen diversity. Quarantine or separation of incoming cattle from established populations reduces disease spread. Controlling visitor access and sanitation of vehicles and equipment prevents mechanical transmission. While complete biosecurity is impractical for most beef cattle operations, attention to pathogen exposure reduction provides meaningful disease reduction.

Management practices during transportation and the arrival period significantly influence BRD risk. Transportation management should minimize trip duration and ensure appropriate loading density, temperature management, bedding, and access to water during long hauls. Rest stops with feed and water access benefit cattle on extended journeys. Gentle handling throughout the process reduces stress and associated immune suppression. Upon arrival, cattle should have immediate access to clean water and palatable hay. Processing procedures should be completed with minimal stress, and multiple-procedure processing may be better split across days to reduce cumulative stress. Adequate bunk space and pen density allow cattle to eat and rest comfortably during the high-risk arrival period.

Nutritional strategies support immune function and stress resilience. Appropriate receiving diets meeting energy and protein needs without excessive concentrate help newly arrived cattle transition successfully. Vitamin and mineral supplementation, particularly vitamins A and E and trace minerals including selenium, copper, and zinc, supports immune competence. Injectable vitamins at arrival address deficiencies that may have developed during marketing and transport. Avoiding digestive upset through appropriate diet formulation and management prevents metabolic stress that could compound immune suppression. Working with nutritionists to develop appropriate receiving and growing diets optimizes cattle health during the critical early feeding period.

Daily management and monitoring for BRD prevention and early detection requires systematic observation and rapid response to early warning signs. Visual assessment of all cattle at least once daily, with twice-daily observation during high-risk periods, should evaluate respiratory rate and effort, attitude and alertness, appetite and feed bunk activity, and any nasal discharge or coughing. Pen riders or health monitors should move through pens on foot or horseback, observing cattle from positions that allow assessment of individual animals. Training observation staff in recognition of early BRD signs ensures consistent detection across personnel. Establishing baseline knowledge of normal cattle behavior allows recognition of subtle changes that precede obvious illness. Recording and communicating observations ensures appropriate response to identified problems.

Housing and environmental management significantly impact BRD risk through effects on pathogen exposure, respiratory irritation, and environmental stress. Feedlot pen design should allow adequate space per animal, typically 150-300 square feet depending on animal size and region. Wind protection through windbreaks reduces cold stress during winter months. Mound provision allows cattle to get out of mud during wet periods. Dust control through water application during dry periods reduces respiratory irritation. While feedlot cattle are typically housed outdoors, any enclosed structures should have adequate ventilation. Hospital pen facilities should provide comfortable conditions for recovering cattle with easy access to feed and water. Attention to environmental factors complements medical intervention in BRD control.

Arrival processing and management programs establish the foundation for cattle health during the high-risk early feeding period. Processing typically includes individual identification, vaccination with appropriate products, deworming, implanting, and sometimes metaphylactic antimicrobial treatment for high-risk cattle. Processing timing relative to arrival varies by operation, with some programs processing upon arrival and others allowing rest periods before handling. Multiple-day processing splits procedures to reduce cumulative stress. Gentle handling throughout processing minimizes stress-related immune suppression. Record keeping during processing documents vaccines and treatments administered, supporting later health management decisions. Working with veterinarians to develop processing protocols appropriate for specific cattle types and risk factors optimizes health outcomes.

Record keeping and monitoring systems support effective BRD management and program evaluation. Individual animal identification enables tracking of health events, treatments, and outcomes. Recording all BRD cases including pull date, clinical signs, temperature, treatment administered, and outcome helps evaluate program effectiveness and identify patterns. Morbidity and mortality tracking by source, arrival date, and pen identifies high-risk populations and time periods. Treatment response monitoring identifies antimicrobial resistance patterns or treatment protocol problems. Production records including arrival weight, growth performance, and carcass data allow evaluation of BRD impact on performance and value. Systematic data collection and analysis drives continuous improvement in BRD prevention and management programs.

Economic considerations permeate all aspects of BRD prevention and management, requiring balanced analysis of costs and benefits. Prevention investments including preconditioning premiums, vaccination costs, and metaphylactic treatment expenses must be weighed against expected disease reduction and performance benefits. Studies generally show favorable returns on prevention investments in high-risk populations. Treatment costs including drug costs and labor must be considered in treatment decisions, though animal welfare remains the primary consideration for individual treatment. Performance losses in recovered cattle affect overall profitability and may influence decisions about marketing timing. Chronic poor performers may generate better returns through early marketing than continued feeding. Working with veterinarians and economists to analyze cost-benefit relationships helps operations make informed decisions about BRD program investments.

All breeds of cattle are susceptible to shipping fever, though breed differences in disease susceptibility have been consistently observed. Bos indicus cattle, including Brahman and related breeds and their crosses, demonstrate somewhat greater resistance to BRD compared to Bos taurus breeds, likely related to differences in immune function, stress tolerance, and environmental adaptation. Among Bos taurus breeds, some studies suggest variation in BRD susceptibility, though results are not entirely consistent across studies. British breeds including Angus and Hereford and Continental breeds including Charolais and Simmental are all susceptible. Within any breed, individual variation in disease susceptibility is substantial, with some cattle remaining healthy despite heavy pathogen exposure while others develop severe disease with apparently minor challenge. This individual variation suggests genetic components to BRD resistance that could potentially be selected for.

Production system characteristics influence BRD risk more substantially than breed genetics for most practical purposes. Feedlot cattle face the highest BRD risk due to the combination of transportation stress, commingling, and intensive management. Within feedlot populations, lightweight calves under 600 pounds have higher morbidity rates than heavier cattle. Cattle from auction markets and those commingled from multiple sources experience higher BRD rates than single-source cattle purchased directly from ranches. Hot or fresh calves shipped immediately after weaning face dramatically higher risk than preconditioned calves. These production system factors dwarf breed effects in determining BRD risk in commercial cattle populations. Understanding these risk factors helps target prevention efforts to highest-risk cattle.

Genetic selection for BRD resistance offers potential for long-term improvement but remains challenging to implement. No simple genetic marker reliably predicts BRD resistance, though research continues to identify genetic factors influencing disease susceptibility. Expected progeny differences (EPDs) for BRD-related traits including respiratory disease, bovine respiratory disease, and docility are becoming available for some breeds, though predictive accuracy remains limited. Selection indexes incorporating health traits provide one mechanism for including BRD resistance in breeding programs. Within-herd selection culling cattle with repeated BRD episodes and retaining cattle that remain healthy despite challenge can gradually shift population genetics toward improved resistance. Avoiding excessive inbreeding maintains genetic diversity supporting robust immune function. Practical genetic improvement for BRD resistance requires balancing health traits against growth, carcass, and reproductive traits within breeding objectives.

Several conditions commonly predispose to or co-occur with shipping fever, creating complex disease situations in affected cattle. Viral respiratory infections with bovine respiratory syncytial virus, parainfluenza-3, infectious bovine rhinotracheitis virus, and bovine viral diarrhea virus frequently precede bacterial BRD by damaging respiratory epithelium and suppressing immunity. BVD is particularly significant as a predisposing factor, with both acute infections and persistently infected (PI) cattle contributing to increased BRD risk in exposed populations. Mycoplasma bovis causes its own pattern of respiratory disease and frequently co-infects with classic BRD pathogens, often leading to treatment-resistant disease and chronic pneumonia. Internal parasitism, nutritional deficiencies, and other stressors compromise immune function and increase BRD susceptibility. Addressing these predisposing conditions through appropriate vaccination, parasite control, and nutrition supports BRD prevention.

Differential diagnosis for cattle presenting with respiratory disease includes conditions other than classic shipping fever that require different management approaches. Interstitial pneumonia patterns including acute bovine pulmonary emphysema and edema occur in cattle on lush pasture and cause severe respiratory distress without the fever typical of bacterial pneumonia. Aspiration pneumonia following drenching accidents has characteristic history and distribution of lung involvement. Lungworm infection causes respiratory signs in grazing cattle. Upper respiratory disease including IBR pharyngitis presents with respiratory difficulty and salivation. Thrombotic meningoencephalitis caused by Histophilus somni presents neurologically but may occur with concurrent respiratory disease. Foreign body pneumonia occurs occasionally. Careful history taking and clinical examination distinguish these conditions from classic shipping fever.

Complications of shipping fever reflect the severe lung damage possible with BRD and affect both immediate outcomes and long-term cattle performance. Chronic pneumonia develops in cattle surviving acute BRD, with persistent lung consolidation, adhesions, and abscess formation affecting respiratory function and performance indefinitely. Pleuritis accompanies severe BRD, adding chest pain and potentially leading to adhesion formation restricting lung expansion. Pericarditis can develop as extension of severe respiratory infection. Polyarthritis occurs with some BRD pathogens, particularly Histophilus somni and Mycoplasma bovis. Lung abscesses create chronic infection foci and serve as sources for ongoing bacterial shedding. These complications emphasize the importance of early, aggressive treatment and comprehensive prevention programs to minimize BRD occurrence and severity.