Introduction
The magnitude and frequency of bovine respiratory disease (BRD) and associated deleterious effects vary by specific production system, phase of production, and operational-level specific prevention and treatment costs. This syndrome can result in permanent pulmonary damage; therefore, the effects of the disease do not end when calf stops showing clinical signs: production and performance impacts can be lifelong. A multi-market, multi-commodity partial equilibrium economic model of the U.S. agricultural industry determined that reducing BRD would increase the supply of beef consequently lowering beef prices, increasing cattle welfare, and benefiting society (Johnson and Pendell, Reference Johnson and Pendell2017). The impacts of BRD can be divided into costs (health-related losses and expenses incurred due to preventative health management, treatment, retreatment, mortality, and labor costs associated with all the above), and reduced income (costs associated with decreased production as measured in the specific system).
Pre-weaning BRD
Respiratory disease in cow–calf operations primarily impacts pre-weaned (less than 7 months old) calves. Two independent surveys conducted with veterinarians and producers elicited the frequency of herds having problems with pre-weaning BRD as well as the estimated within-herd prevalence (Woolums et al., Reference Woolums, Berghaus, Smith, White, Engelken, Irsik, Matlick, Jones, Ellis, Smith, Mason and Waggoner2013, Reference Woolums, Berghaus, Smith, White, Engelken, Irsik, Matlick, Jones and Smith2014). In both surveys, approximately 20% of the herds reported a problem with pre-weaning or nursing calf BRD. This illustrates the clustered nature of this syndrome and the relative importance of understanding the herd situation. The within-herd incidence for BRD has been estimated at 5–15% in afflicted herds (Hanzlicek et al., Reference Hanzlicek, Renter, White, Wagner, Dargatz, Sanderson, Scott and Larson2013; Woolums et al., Reference Woolums, Berghaus, Smith, White, Engelken, Irsik, Matlick, Jones, Ellis, Smith, Mason and Waggoner2013, Reference Woolums, Berghaus, Smith, White, Engelken, Irsik, Matlick, Jones and Smith2014). The frequency of BRD cases within a herd with pre-weaning BRD can vary from year to year. A long-term study (1983–2002) of a single herd illustrated year to year variation ranging from within-herd morbidity incidence of 3.3 to 23.6% with an overall average of 10.5% (Snowder et al., Reference Snowder, Van Vleck, Cundiff and Bennett2005). Large year-to-year fluctuations were present with periods of high incidence often followed by a decrease. Pre-weaning disease incidence tends to peak between 80 and 120 days of age.
In cow–calf herds, the primary source of income is the sale of calves. This income is influenced by both the number of calves sold and the weight of these calves; thus, any health issue that decreases the weight or the number sold has a direct impact on the gross income and thus profitability of the operation. Many calves afflicted with pre-weaning BRD will be treated with antimicrobials, which adds cost of the antimicrobial as well as labor associated with catching and treating the calves. Total pre-weaning mortality risk from all causes is 3.6% in U.S. cow–calf herds: BRD makes up the primary cause of mortality post 3 weeks of age and represents 16.4% of total death loss in these pre-weaned beef calves (or a 0.5% of all mortality). The impact of BRD on growth performance in pre-weaned calves is poorly defined but is likely to result in an additional source of economic loss along with the known impact of pre-weaning BRD on the reduced number of calves sold at weaning due to mortality and the costs associated with treatment.
Post-weaning BRD
BRD is the most common animal health problem after calves destined for slaughter are weaned and accounts for a high percentage of feedlot morbidity and mortality. This syndrome has been estimated to impact 16.2% of all cattle placed on feed (USDA, 2011) or four times more cattle than affected by the next most commonly reported disease (digestive disease). Yard size plays a role in the level of BRD with yards greater than 8000 head estimating that 17.2% of cattle are affected and yards less than 8000 head reporting 9% impacted (USDA, 2011). The overall average number of cattle impacted can be deceptive as post-weaning BRD has a skewed distribution when evaluated on a lot or cohort level. Most cohorts have low or no BRD cases while some cohorts will have high (greater than 10–15%) occurrence of BRD. Most BRD cases are first identified within the first 45–60 days of arrival.
Post-weaning phase profitability is heavily influenced by purchase price, efficiency of weight gain, feed cost, and sale price of the animals. BRD can influence weight gain and sale price through negative impacts. The total cost of BRD is the sum of the expenses incurred treating identified cases and the negative weight-gain performance effects through the feeding phase. Several studies have evaluated this impact and determined that the cost of BRD on individual calves that survive the feeding phase can be from $45 to $92 per head, and 50–60% of this cost is related to lost performance (Fulton et al., Reference Fulton, Cook, Step, Confer, Saliki, Payton, Burge, Welsh and Blood2002; Schneider et al., Reference Schneider, Tait, Busby and Reecy2009; Brooks et al., Reference Brooks, Raper, Ward, Holland, Krehbiel and Step2011). The total cost of BRD for cattle that survive to slaughter does not account for death loss which adds further negative impact on profitability of the management cohort.
Treatment impacts
The cost of a single treatment has been estimated at $23.60 in 2011, nearly doubling the cost of treatment of $12.59 in 1999 (USDA, 2011). The U.S. cattle on feed is approximately 11.75 million head in May 2019 (USDA NASS, 2019) and assuming twice a year inventory turnover, the total cost of treatment for BRD is $88.7 million for treating 16.2% of the cattle. This treatment cost is primarily based on the antimicrobial cost alone and does not include labor or any of the potential performance impacts of BRD.
When calves are treated multiple times due to failure to recover normal health as determined by clinical assessment, the losses are exacerbated. The calves treated three or more times demonstrated $70–$90 net return losses likely due to the severity of illness which merited three treatments (Cernicchiaro et al., Reference Cernicchiaro, White, Renter and Babcock2013). In another study, calves were sorted into pens based on the number of times they were treated for BRD and fed to a common body composition. The study found that the increased number of BRD treatments was associated with increased days on feed and decreased hot carcass weight, rib eye area, and quality grade (Wilson et al., Reference Wilson, Step, Maxwell, Gifford, Richards and Krehbiel2017). Even when the outcome of BRD treatment is successful return to normal health, BRD has a negative economic impact on feedyard and backgrounding operations.
Metaphylaxis is the treatment of all cattle at arrival to a feedyard or backgrounding operation for the control of BRD; and this practice is commonly utilized on cattle at high risk for BRD (Nickell and White, Reference Nickell and White2010). Depending on the antimicrobial agent, metaphylaxis may reduce morbidity by up to 50% and also impact overall mortality (Abell et al., Reference Abell, Theurer, White, Larson and Apley2017). The reduction in disease risk results in decreased performance losses and the value of metaphylaxis has been estimated to be at least $532 million to the U.S. feed cattle industry (Dennis et al., Reference Dennis, Schroeder, Renter and Pendell2018). In addition to increased estimated net returns associated with metaphylaxis, the distribution of net returns is also more narrow allowing better risk management. Overall, metaphylaxis is an important tool to reduce the negative impacts of BRD.
Performance impacts
In addition to the immediate costs of treatment and risk for death loss, cattle impacted by BRD have lifelong consequences. Feeder calves and cattle treated for BRD have a mean weight gain reduction of 0.07 kg d−1, and depending on the production system this can be a 3–7% daily reduction in performance which can have a large economic impact (Thompson et al., Reference Thompson, Stone and Schultheiss2006; Theurer et al., Reference Theurer, White, Larson and Schroeder2015a, Reference Theurer, White and Renter2015b).
The cumulative efficiency of weight gain over the life of an animal impacts the final body weight, one of the key drivers of gross income in the finishing phase of production, and BRD has been shown to reduce this weight by 4–11 kg compared to non-treated calves (Reinhardt et al., Reference Reinhardt, Busby and Corah2009; Schneider et al., Reference Schneider, Tait, Busby and Reecy2009). Cattle treated for BRD are reported to have a 3–8.6 kg reduction in hot carcass weight (primarily due to reduction in musculoskeletal growth) compared to non-treated cattle. BRD also modifies the characteristics of the carcass at the time of harvest. Calves with BRD can have reduced likelihood to grade choice or above (having a higher percent intramuscular fat) by 4–30% (Cernicchiaro et al., Reference Cernicchiaro, White, Renter and Babcock2013). Therefore, economic losses associated with BRD are not limited to treatment cost or mortality risk, but even calves that are treated and survive the disease have long-term negative economic effects.
Diagnostic impacts
The primary modality for BRD diagnosis is daily or more frequent visual observation of cattle to detect the clinical signs of disease and requires that beef producers make significant investment in labor and facilities resources. Determining the accuracy of BRD diagnosis in clinical settings is challenging due to the lack of a gold standard test. Studies have shown variation in the estimates of sensitivity and specificity, but concluded that clinical diagnosis is imperfect and the extent of imperfect assessment varies among studies (White and Renter, Reference White and Renter2009; Timsit et al., Reference Timsit, Dendukuri, Schiller and Buczinski2016). The lack of diagnostic accuracy impacts one's confidence in the assessment of true BRD treatment success and subsequent performance and economic impacts. A study using an economic model to identify the impact of potential improvements in BRD diagnostic accuracy identified that improving specificity of BRD diagnostics could increase value more than improving sensitivity (Theurer et al., Reference Theurer, White, Larson and Schroeder2015a). Because clinical diagnosis based on visual appraisal is imperfect, designing optimal testing strategies based on follow-up testing on cattle that either do or do not meet the case definition for BRD can help reduce BRD impact. The cost of BRD misdiagnosis is influenced by the expected and actual BRD incidence in the group, and the potential value of additional follow-up testing of cattle based on whether they are presumptively identified as meeting or not-meeting the case definition for BRD can be evaluated to determine optimum testing strategies for specific cattle and economic situations (Theurer et al., Reference Theurer, White and Renter2015b).
Conclusions
BRD is one of the most frequent diseases of cattle and impacts animal welfare, performance, and economic parameters. The disease occurs in multiple phases of beef cattle production including sporadic, herd-level clustered cases in pre-weaning environments, and lot-level clustered cases in the post-weaning phases. Compared to healthy animals, BRD-afflicted calves have increased mortality risk, increased treatment costs, and decreased live-animal and carcass performance. Additionally, the lack of gold standard diagnostics increases the overall cost of BRD due to expenses associated with misdiagnoses. Several tools are available to prevent, manage, and treat BRD cases and some of these technologies (e.g. metaphylaxis) have a large value to the cattle industry.
