Bovine Respiratory Disease In Calves Research Articles

Multi-omics investigation into long-distance road transportation effects on respiratory health and immunometabolic responses in calves

BackgroundLong-distance road transportation is a common practice in the beef industry, frequently resulting in bovine respiratory disease (BRD) and compromised growth performance. However, a comprehensive investigation integrating clinical performance, physiological conditions, and nasopharyngeal microflora remains lacking.MethodsThis study aimed to evaluate the respiratory health and immunometabolic status of 54 beef calves subjected to a 3000-km journey. The respiratory health of calves was monitored over 60 days post-arrival using a modified clinical scoring system. Nasopharyngeal microflora and venous blood samples were collected at 3 time points: before transportation (A), 30 days post-arrival (B), and 60 days post-arrival (C), for 16S rRNA microbiomics, whole-blood transcriptomics, serum metabolomics, and laboratory assays.ResultWithin the first week post-arrival, the appetite and mental scores of calves dropped to zero, while other respiratory-related scores progressively declined over the 60 days. The α-diversity of nasopharyngeal microflora in calves was similar at time points A and B, both significantly higher than at time point C. The structure of these microbial communities varied significantly across different time points, with a notably higher relative abundance of BRD-related genera, such as Pasteurella and Mannheimia, detected at time point A compared to B and C. The composition and gene expression profiles of circulating blood cells at time point A were significantly different from those at B and C. Specifically, higher expression levels of oxidative- and inflammatory-related genes, cytokines, and enzymes were observed at time point A compared to B and C. Higher levels of catabolism-related metabolites and enzymes were detected at time point A, while higher levels of anabolism-related metabolites and enzymes were observed at time points B and C. Additionally, significant correlations were found among microorganisms, genes, and metabolites with differing abundances, expression levels, and concentrations across time points. Stronger correlations were observed between calves’ performance and nasopharyngeal microflora and immunometabolic status at time point A compared to B or C.ConclusionsCollectively, these results confirm that 3000 km of road transportation significantly alters the composition and gene expression profiles of circulating white blood cells in calves, affects their metabolic processes, disrupts the balance of the respiratory microbial community, and leads to pronounced respiratory symptoms that persist for at least 60 days. During this period, the influenced composition and gene expression of circulating blood cells, metabolic processes, and nasopharyngeal microbial community gradually return to equilibrium, and the respiratory symptoms gradually diminish. This observational research indicates that transportation induces BRD in calves by disrupting the homeostasis of their immune function, metabolic processes, and nasopharyngeal microbial community. However, these results and their underlying molecular mechanisms warrant further validation through well-designed in vivo and in vitro confirmatory experiments with larger sample size.6SLnr553TSMBqvLo9hfCJxVideo

Local and systemic humoral immune responses to Histophilus somni recombinant antigens administered intranasally and subcutaneously to dairy calves

Bovine respiratory disease (BRD) causes significant economic losses in dairy calves. Induction of an early immune response via parenteral vaccination is complicated by the interference of colostral immunity. In this study, we investigated early immunization against selected conserved bacterial antigens. Calves were vaccinated twice intranasally and then subcutaneously with Histophilus somni recombinant proteins (rOMP40 or rHsp60) mixed with one of two adjuvants: CpG ODN2007 or MPLA. The control group (Con) was treated with PBS. The first immunization was done between 24 and 48 h of life and then twice in two weeks intervals. Blood, nasal, and saliva secretion samples were collected directly before vaccination (S1–S3) and then on 42–44 (S4) and 59–61 (S5) day of life. Antibodies (IgG1/IgG2/IgM/IgA in serum; IgG1/IgA in secretions) against both vaccine antigens were quantified in all samples. Intranasal and subcutaneous vaccinations using the described formulas did not increase antibody reactivity against the tested proteins. The reactivity of serum IgG1, IgM, and IgA anti-rOMP40 antibodies was significantly higher in S1 in all groups than that in the other samplings (p˂0.01). Significant differences in the reactivity of serum anti-rOMP40 antibodies between groups were identified in S1 (IgA reactivity was higher in the CpG vs. MPLA group; p < 0.05), S4 (IgM reactivity was higher in Con vs. CpG group; p < 0.05), and S5 (IgG1 reactivity was higher in MPLA vs. Con group; p < 0.05). The lack of consistent changes in antibodies after immunization (S4 and S5) hinders the drawing of conclusions regarding the effect of immunization on antibody reactivity. In the future, establishing a proper immunization window and adjuvants for nasal vaccines against bacterial pathogens causing BRD in calves remains to be determined.

Choosing the optimal combination of lungs lobe evaluation during focused pulmonary ultrasonography in calves

Bovine respiratory disease (BRD) poses significant challenges on beef and dairy farms, impacting mortality rates, animal welfare, and production efficiency. Although pulmonary ultrasonography is highly sensitive and specific for monitoring lung lesions and diagnosing BRD, its practical application could be optimized by focusing on the most commonly affected lung lobes. This study first evaluated the efficacy of focused lung ultrasonography for diagnosing BRD in calves, examining individual lung lobes and their associations versus the extensive lung scanning under various disease prevalence scenarios. Then, the relationship between individual and combined clinical respiratory signs vs lung consolidation was analyzed. In a combined analysis, 193 Holstein calves from a longitudinal study and 112 Angus calves from a cross-sectional study underwent a total of 1265 complete bilateral thoracic ultrasonographic evaluations from 1 to 6 mo of age. Then, it was assessed the agreement and sensitivity of specific lung lobe combinations compared with the findings from total lung ultrasonography. The Classification and Regression Tree (CART) algorithm was used to suggest an optimal examination sequence, and logistic regression was applied to associate specific clinical signs with the presence of lung consolidation adjusting for breed and calf age. Findings reveal that the most sensitive areas are cranial (K: 0.867; Se: 84.7%) and the caudal (K: 0.433; Se: 40.3%) portions of the right cranial lobe, the caudal portion (K: 0.235; Se: 20.6%) of the left cranial lobe, and the middle lobe (K: 0.25; Se: 22%). The optimal lobe combinations for focused lung ultrasonography were identified as the right cranial lobe paired with either the left cranial lobe or the middle lobe. Focused techniques achieved sensitivity over 94% and maintained good agreement. Using these focused techniques were relatively robust to various true lung consolidation scenarios. CART analysis recommended initiating examinations with the right cranial lobe, proceeding to the left cranial lobe, and concluding with the middle lobe. While spontaneous cough was linked to pneumonia presence, reliance on a single clinical sign is not advised due to low sensitivity (26.8%) and high specificity (85.4%); it should merely prompt further ultrasound assessment. In conclusion, focused lung ultrasonography, especially utilizing the right cranial lobe in conjunction with the left cranial lobe or the middle lobe, emerged as effective strategies for focused pulmonary ultrasonography, preserving the accuracy of the results.

Detection of calf abnormal respiratory behavior based on frame difference and improved YOLOv5 method

Bovine respiratory disease (BRD) is the leading cause of death in calves. Abnormal respiratory behavior (ARB) is one of the prevalent clinical signs of BRD in calves, manifesting as tachypnea and visible chest and abdominal respiration. This paper proposed a calf ARB detection method based on frame difference (FD) and improved YOLOv5 to increase detection efficiency and achieve automatic detection. A total of 1400 video segments, each lasting about 30 s, were collected from 10 calves with ARB and 40 with normal respiratory behavior (NRB). First, a squeeze-and-excitation (SE) model was added to the YOLOv5 network to realize key feature extraction of the calf head and trunk. Next, the model was trained and tested using 5520 images obtained after You Only Cut Once (YOCO) image enhancement. Next, FD was used to obtain the shaking pixels and determine the proportion of trunk shake (PTS) for each frame of the calf image. Then, 1250 video segments were divided into 3 s video units. Finally, 2500 ARB and 2500 NRB 3 s video units were manually selected for the calf ARB detection set. The maximum, minimum, mean, variance and standard deviation of PTS within each 3 s video unit were extracted as feature values and input to support vector machine (SVM). The results showed that the improved YOLOv5 network achieved high mAP50 of 98.2% and mAP50:95of 92.6%, which was 0.9% and 2.3% higher than the baseline YOLOv5. Meanwhile, ARB could be detected with an accuracy of 96.80%, a sensitivity of 95.20%, a specificity of 98.40%, and a precision of 98.35% after 5-fold cross-validation. The results indicated that the proposed method could effectively detect calf trunk and head and be used for calf ARB detection, providing a technical reference for calf ARB detection.

Prevalence of respiratory disease in Irish preweaned dairy calves using hierarchical Bayesian latent class analysis.

Bovine respiratory disease (BRD) has a significant impact on the health and welfare of dairy calves. It can result in increased antimicrobial usage, decreased growth rate and reduced future productivity. There is no gold standard antemortem diagnostic test for BRD in calves and no estimates of the prevalence of respiratory disease in seasonal calving dairy herds. To estimate BRD prevalence in seasonal calving dairy herds in Ireland, 40 dairy farms were recruited and each farm was visited once during one of two calving seasons (spring 2020 & spring 2021). At that visit the prevalence of BRD in 20 calves between 4 and 6 weeks of age was determined using thoracic ultrasound score (≥3) and the Wisconsin respiratory scoring system (≥5). Hierarchical Bayesian latent class analysis was used to estimate the calf-level true prevalence of BRD, and the within-herd prevalence distribution, accounting for the imperfect nature of both diagnostic tests. In total, 787 calves were examined, of which 58 (7.4%) had BRD as defined by a Wisconsin respiratory score ≥5 only, 37 (4.7%) had BRD as defined by a thoracic ultrasound score of ≥3 only and 14 (1.8%) calves had BRD based on both thoracic ultrasound and clinical scoring. The primary model assumed both tests were independent and used informed priors for test characteristics. Using this model the true prevalence of BRD was estimated as 4%, 95% Bayesian credible interval (BCI) (1%, 8%). This prevalence estimate is lower or similar to those found in other dairy production systems. Median within herd prevalence varied from 0 to 22%. The prevalence estimate was not sensitive to whether the model was constructed with the tests considered conditionally dependent or independent. When the case definition for thoracic ultrasound was changed to a score ≥2, the prevalence estimate increased to 15% (95% BCI: 6%, 27%). The prevalence of calf respiratory disease, however defined, was low, but highly variable, in these seasonal calving dairy herds.

Ultrasonographic diagnosis of clinical and subclinical bovine respiratory disease in Holstein calves.

Background and Aim:Bovine respiratory disease (BRD) is the main cause of death in calves, and early BRD diagnosis saves lives. This study aimed to diagnose clinical and subclinical BRD in calves by assessing some biochemical alterations and ultrasonography (USG).Materials and Methods:Fifty-four Holstein dairy calves in Al-Sharqiyah Province, Egypt, were used in the study. They were divided into three groups. The first control group consisted of 10 clinically healthy calves. The second group consisted of 34 calves suffering from clinical lower respiratory tract disorders. The third group consisted of 10 subclinical BRD-affected calves. Ultrasonographic examinations of chest and thoracic ultrasound scoring were performed once per 2 weeks for each calf. Blood samples were collected for serum separation to measure albumin (ALB), total protein (TP), ALB, globulin, and haptoglobin (HP).Results:The USG revealed small consolidation areas within an aerated lung lobe, a hypoechoic parenchyma of the entire distal lung lobe, and a hypoechoic-circumscribed structure surrounded by an echogenic wall appeared within the lung tissue in calves that suffered from lobular pneumonia, lobar pneumonia, and lung abscess, respectively. However, subclinical cases showed a small consolidation area in the cranial aspects of the right cranial lung lobe. The ultrasound lung score (ULS) was greater in clinical than in subclinical cases. The BRD-affected calves recorded significant increases in serum TP, globulin, and HP. Meanwhile, serum ALB decreased significantly.Conclusion:Thoracic ultrasound had a reliable tool in the BRD diagnosis, especially in the early prediction of subclinical cases in newborn calves. In addition, the ULS appeared to be a better classifier than the clinical respiratory score (CRS) for BRD diagnosis. On the other side, it was found that regression models were very useful in assessing the prediction of biochemical blood parameters based on the ULS and CRS in diseased cases.

Modelling Shows the Negative Impact of Age Dependent Pharmacokinetics on the Efficacy of Oxytetracycline in Young Steers.

The effect of age dependent pharmacokinetics (PK) on the clinical efficacy of oxytetracycline (OTC) against Bovine Respiratory Disease (BRD) in beef cattle was studied, using a Physiologically Based Pharmacokinetic (PBPK) model. The model includes a bodyweight dependent renal clearance. To mimic/reproduce the long terminal half-live a bone forming tissue compartment was considered. Data for the development, calibration and validation of the model were obtained from public literature. To integrate the PK with the pharmacodynamics (PD) of OTC, Monte Carlo simulations were performed using this PBPK model to predict time-concentration curves for two commonly used dosing regimens of short-acting and long-acting injectable OTC formulations in virtual populations of 5,000 steer calves of 100 kg and 400 kg. These curves were then used to calculate the value of the PKPD index for OTC, which is the ratio of the area under the concentration-time curve for 24 h (AUC24h) over the minimum inhibitory concentration (MIC) of the target pathogen (AUC24h/MIC). The MIC values were for Mannheimia haemolytica, the dose-limiting pathogen for BRD. This integration of PBPK and PD for OTC used for the treatment of BRD in calves indicated that the Probability of Target Attainment (PTA) was sufficient for efficacy in calves of 400 kg, but insufficient for calves of 100 kg, when using a long acting dosing regimen of 20 mg/kg BW, twice, with a 48-h interval. The use of a dosing regimen of 10 mg/kg BW/day for 4 days predicted sufficient PTAs in both age groups.

Use of Thoracic Ultrasonography to Improve Disease Detection in Experimental BRD Infection.

Bovine respiratory disease (BRD) is caused by complex interactions between viral and bacterial pathogens, host immune status, and environmental stressors. In both clinical and research settings, current methods for detecting BRD in calves commonly focus on visual indicators such as attitude, nasal discharge, and cough, in addition to vital signs such as rectal temperature and respiration rate. Recently, thoracic ultrasonography (TUS) has become more commonly used in clinical settings, in addition to physical examination to diagnose BRD. To assess the value of performing TUS during experimental BRD infection, 32 calves were challenged with bovine respiratory syncytial virus, to mimic a viral infection, and 30 calves were infected with Mannheimia haemolytica, to mimic a bacterial infection. TUS was performed at regular intervals using a standardized method and scoring system in addition to daily clinical scoring. Although overall correlations between clinical scores and TUS scores were generally weak (maximum R2 = 0.3212), TUS identified calves with abnormal lung pathology that would have otherwise been misclassified on the basis of clinical scoring alone, both on arrival and throughout the studies. In addition, TUS had an increased correlation with gross lung pathology on necropsy (maximum R2 = 0.5903), as compared to clinical scoring (maximum R2 = 0.3352). Our results suggest that TUS can provide additional information on calf health at enrollment and throughout a study and may provide an alternative to terminal studies, due to the high correlation with lung pathology at necropsy.

Use of thoracic ultrasound on Scottish dairy cattle farms to support the diagnosis and treatment of bovine respiratory disease in calves.

Bovine respiratory disease (BRD) is common in cattle youngstock on UK dairy farms. The current diagnostic methods lack sensitivity and specificity. Thoracic ultrasound (TUS) is a relatively new BRD diagnostic tool with increased accuracy. Data were collected from TUS examinations of 347 calves on Scottish dairy farms and compared to farmer BRD treatment rates. A calf health scoring tool was used to collect information on youngstock health and management on these farms. Of 347 ultrasonographic examinations, 53 (15.3%) were classified as abnormal and 294 (84.7%) as normal. Of the 53 calves classified as abnormal, only 13 (24.5%) were treated by the farmer; however, of the 294 classified as normal, 22 (7.5%) were treated. The results indicated farmers were misdiagnosing BRD in youngstock. Use of TUS on UK farms may improve diagnostic rates and accuracy, reduce the unnecessary use of antimicrobials and demonstrate the value of preventive healthcare programmes.

Decision tree analysis for pathogen identification based on circumstantial factors in outbreaks of bovine respiratory disease in calves

Respiratory tract infections continue to be a leading cause of economic loss, hampered animal welfare and intensive antimicrobial use in cattle operations, worldwide. To better target antimicrobial therapy, control and prevention towards the involved pathogens, there is a growing interest in microbiological tests on respiratory samples. However, these tests are time consuming, cost money and sampling might compromise animal welfare. Therefore, the objective of the present study was to develop immediately applicable decision trees for pathogen identification in outbreaks of bovine respiratory disease based on circumstantial factors. Data from a cross sectional study, involving 201 outbreaks of bovine respiratory disease in dairy and beef farms between 2016 and 2019 was used. Pathogens were identified by a semi-quantitative PCR (polymerase chain reaction) on a pooled non-endoscopic broncho-alveolar lavage sample from clinically affected animals. Potential risk factors of involved animals, environment, management and housing were obtained by enquiry. Classification and regression tree analysis was used for decision tree development with cross-validation. Different trees were constructed, involving a general 3-group classification tree (viruses, Mycoplasma bovis or Pasteurellaceae family) and a tree for each single pathogen. The general 3- group classification tree was 52.7 % accurate and had a sensitivity of 81.5 % and a specificity 52.2 % for viruses, respectively 51.7 % and 84.4 % for M. bovis and 28.9 % and 93.6 % for Pasteurellaceae. The single-pathogen trees were more specific than sensitive: Histophilus somni (Se = 25.8 %; Sp = 94.5 %), Mannheimia haemolytica (Se = 69.2 %; Sp = 70.6 %), bovine coronavirus (Se = 42.2 %; Sp = 89.6 %) and bovine respiratory syncytial virus (Se = 34.0 %; Sp = 96.6 %). For Pasteurella multocida, M. bovis and parainfluenzavirus type 3 no meaningful tree was obtained. The concept and trees are promising, but currently lack sensitivity and specificity in order to be a reliable tool for practice. For now, the obtained trees can already be informative for decision making to some extend depending on the end node in which an outbreak falls.

Nutraceutical intervention with colostrum replacer: Can we reduce disease hazard, ameliorate disease severity, and improve performance in preweaned dairy calves?

The objective of this randomized clinical trial was to determine if an intervention with colostrum replacer (CR; Premolac Plus, Zinpro; 125 g/d fed for 3 d) or a placebo milk replacer (Cows Match, Land O'Lakes Inc.; 125 g/d for 3 d) following a triggered alarm could ameliorate disease bouts in dairy calves. The alarm was set to detect negative deviations of milk intake (20% reduction) or drinking speed (30% reduction) in relation to a calf's 12-d rolling average feeding behavior. Calves were enrolled on this study (n = 42 CR, n = 42 placebo) when they triggered an alarm from d 14 to 50 on the feeder before weaning. Once calves were enrolled, calves received a bottle of either 125 g of CR or milk replacer mixed with 1 L of water for 3 d. Calves were enrolled on the automated milk feeder at age 4.0 ± 2.0 d (mean ± SD), were offered 10 L/d of the same milk replacer fed as a placebo, and had ad libitum access to calf starter measured by automated feeders. Weaning began at d 50, with 50% reduction of milk replacer across 14 d, and an additional 20% reduction for another 7 d before weaning at d 70. Calves were health scored from birth to 2 wk postweaning (88 ± 2.0 d of age) daily for bovine respiratory disease (BRD) and diarrhea, and were weighed and scored using lung ultrasonography twice weekly. A BRD score ≥5 and an area of consolidated lung ≥3.0 cm2 was considered BRD positive; diarrhea was defined as a watery fecal consistency that sifted through the bedding. The effect of CR on BRD and diarrhea likelihood were calculated with logistic models; the 7 d before and after an alarm were fixed effects, with milk intake as a covariate. A Cox proportional hazards model evaluated the effect of CR on the hazard of being positive for BRD and diarrhea following enrollment, with sex as a fixed effect in the diarrhea model. The effect of CR on average daily gain the week following intervention was evaluated with linear modeling with repeated measures, and birth date was a random effect. After intervention, placebo calves had 1.64 (95% CI: 1.11-2.43) times greater odds of having a BRD bout compared with CR calves for the 7 d following intervention. Moreover, placebo calves had 1.50 (95% CI: 1.11-2.08) times greater odds of having lobar lung consolidation in the 7 d after intervention than CR calves. No difference was found in the likelihood of diarrhea in the 7 d after intervention (odds ratio: 0.91; 95% CI: 0.71-1.16). However, placebo calves had a 2.38 (95% CI: 1.30-4.33) times greater hazard of incurring BRD in the 14 d after intervention. Average daily gain was not associated with an intervention with CR for the 7 d after intervention (placebo: 0.73 ± 0.07 kg/d; CR: 0.70 ± 0.08 kg/d; LSM ± SEM). These results suggest CR may reduce BRD likelihood but did not influence growth in calves offered high allowances of milk. Future research should examine which properties of CR ameliorate BRD in calves.

Early detection of bovine respiratory disease in calves by induced cough

100 Holstein calves aged 7-14 days investigated the effectiveness of various cough provocation methods for bovine respiratory disease early detection. The animals were evaluated according to the clinical scoring system WI, to provoke cough in calves, they performed: 15-minute run, 30-second apnea on exhalation, palpated the trachea in its lower third region and intravenously injected 0.6% hydrogen peroxide solution at 0.9 % sodium chloride solution at a dose of 0.4 ml per kg of body weight to induce H2O2-induced bronchoconstriction. Out of 100 calves, 60 were selected without spontaneous cough and with a WI clinical score of 3 points or less, in which the leukocyte count, differential leukocyte count, neutrophil-to-lymphocyte ratio, nuclear shift index, and pH of exhaled breath condensate and the hydrogen peroxide concentration in exhaled breath. For 2 weeks, these animals were monitored daily for the bovine respiratory disease signs. It was established that 30-second apnea and H2O2-induced bronchoconstriction allow diagnosing bronchitis in calves 6-12 days before its symptom complex (peak) development when other symptoms are still absent and WI clinical score is 3 points or less. However, already at this disease stage, animals exhibit leukocytosis, increased serum content of haptoglobin, decreased pH exhaled breath condensate, and increased the hydrogen peroxide concentration in exhaled breath. The trachea lower third cough on palpation appearance indicates the tracheobronchitis early manifestations presence in calves. Trachea lower third Sequential palpation and 30-second apnoea to provoke coughing in calves allows not only the bovine respiratory disease early detection, but also to differentiate early bronchitis and tracheobronchitis manifestations.

Preweaning cost of bovine respiratory disease (BRD) and cost-benefit of implementation of preventative measures in calves on California dairies: The BRD 10K study

Bovine respiratory disease (BRD) is a multifactorial disease that is estimated to affect 22% of preweaned dairy calves in the United States and is a leading cause of preweaning mortality in dairy calves. Overall cost of calfhood BRD is reflected in both the immediate cost of treating the disease as well as lifetime decrease in production and increased likelihood of affected cattle leaving the herd before their second calving. The goal of this paper was to develop an estimate of the cost of BRD based on longitudinal treatment data from a study of BRD with a cohort of 11,470 preweaned dairy calves in California. Additionally, a cost-benefit analysis was performed for 2 different preventative measures for BRD, an increase of 0.47 L of milk per day for all calves or vaccination of all dams with a modified live BRD vaccine, using differing assumptions about birth rate and number of calves raised per year. Average short-term cost of BRD per affected calf was $42.15, including the use of anti-inflammatory medications in the treatment protocols across all management conditions. The cost of treating BRD in calves appears to have increased in recent years and is greater than costs presented in previous studies. A cost-benefit analysis examined different herd scenarios for a range of cumulative incidences of BRD from 3 to 25%. Increasing milk fed was financially beneficial in all scenarios above a 3% cumulative incidence of BRD. Use of a modified live vaccine in dams during pregnancy, examining only its value as a form of BRD prevention in the calves raised on the farm, was financially beneficial only if the cumulative incidence of BRD exceeded 10 to 15% depending on the herd size and whether the dairy farm was raising any bull calves. The cost-benefit analysis, under the conditions studied, suggests that producers with high rates of BRD may benefit financially from implementing preventative measures, whereas these preventative measures may not be cost effective to implement on dairy farms with very low cumulative incidences of BRD. The long-term costs of calfhood BRD on lifetime productivity were not factored into these calculations, and the reduction in disease may be associated with additional cost savings and an improvement in calf welfare and herd life.

Validating loci associated with bovine respiratory disease complex in pre-weaned Holstein calves.

Bovine respiratory disease (BRD) is considered one of the most economically important diseases in the cattle industry. Ultimately, the selection of cattle that are less susceptible to disease will allow producers to reduce the prevalence of BRD and lessen its economic impact. The objective of this study was to validate previously identified loci associated with susceptibility to BRD in an independent population of 140 pre-weaned Holstein calves from Wisconsin (WI). Using the McGuirk health scoring system, calves were classified as either clinically affected with BRD (n=35) or healthy (n=105). Additive genotypic tests were performed for genomic regions previously associated with susceptibility to BRD in calves from California (CA) and New Mexico (NM). Using this method, 4 loci (P<0.01) consisting of 10 SNP were validated in the WI population, including 2 loci from CA, 1 locus from NM, and 1 locus from a combined CA+NM population. Most of the positional candidate genes and transcription factor binding site motifs associated with these loci have functions related to innate and adaptive immune responses. The validation of loci associated with susceptibility to BRD in independent populations allows producers to more reliably select cattle that are less susceptible to BRD, improving animal welfare, decreasing the annual revenue losses, and lowering the prevalence of the disease.

Antimicrobial usage for the treatment on respiratory diseases in calves

Bovine respiratory disease (BRD) is a major concern on calf health. In the USA, BRD explains 24% and 59% of pre-weaned and weaned calf mortality, respectively. This important disease results in over 91% of affected calves being treated with antimicrobials. Our objective was to conduct a systematic review of the quality of published peer-review studies evaluating the efficacy of antimicrobials for the treatment of BRD in calves.

Development of a novel clinical scoring system for bovine respiratory disease (BRD) in weaned dairy calves

Bovine respiratory disease (BRD) continues to impact the welfare of dairy calves and the economics of dairy production. As a common cause of morbidity and mortality among dairy calves, BRD was responsible for 46.5% of deaths after weaning and was observed in 11.2% of weaned animals on heifer-raising operations. Costs involved with the disease reach beyond the treatment of clinically ill animals and include reduced growth, reduced milk production, impaired fertility, and premature culling in the first lactation. The prompt and correct diagnosis of BRD is challenging on farms, especially in weaned dairy calves. Weaned dairy calves are typically housed in larger group pens where there is often a lack of restraint and where it is more difficult to monitor them closely. As a result of challenges in correctly diagnosing BRD, cases often become neglected until they are more severe. Several clinical scoring systems to detect BRD in calves have been published. However, available BRD scoring systems for weaned dairy calves are mostly based on data from calves experimentally infected with specific pathogens. The objective of the present study was to develop and validate a scoring system for weaned dairy calves housed in group pens in an on-farm setting that minimizes calf handling.

Effect of the environment on the risk of respiratory disease in preweaning dairy calves during summer months

Heat stress has the potential to adversely affect the physiology, passive immunity, and growth of preweaning dairy calves, increasing their risk of respiratory disease. The effect of heat stress on the risk for bovine respiratory disease (BRD) may be mediated in part through housing, ventilation, and management factors. As a result, differences may exist in meteorological measures recorded in the calf-rearing area (macroenvironment) and within a calf's enclosure (microenvironment). The objective of this prospective cohort study was to evaluate and compare the association between exposure to temperature and humidity measured at the macro- and microenvironment, and BRD in preweaning dairy calves; a secondary objective was to evaluate the correlation between the macro- and microenvironment. A cohort of 252 calves from 4 premises in central San Joaquin Valley, California (CA), was followed and evaluated for development of respiratory disease using the CA BRD scoring system for preweaning dairy calves, a standardized and validated scoring system. During this time, the meteorological conditions of the calf-rearing area and the within-hutch environment were measured and showed a significant correlation with regard to temperature and humidity. Mixed effects logistic regression and survival analysis were used to analyze the association between the exposures daily environmental measures of temperature, humidity, and temperature-humidity index (THI) and the outcome BRD, adjusted for dairy premises, calf age, sex, and breed. Results showed a significant positive association between daily maximum temperature and BRD in both the calf's macroenvironment [odds ratio = 1.121 (95% confidence interval (CI) = 1.029-1.222)] and microenvironment [odds ratio = 1.203 (95% CI = 1.020-1.418)]. Estimated hazard rates also showed a significant positive association between BRD and daily maximum temperature in both the macroenvironment [hazard ratio = 1.127 (95% CI = 1.053-1.206)] and microenvironment [hazard ratio = 1.119 (95% CI = 1.047-1.197)]. In contrast, we found no association between daily maximum humidity in a calf's microenvironment and BRD. Daily maximum THI within the hutch was significantly associated with only the rate of BRD cases [hazard ratio = 1.070 (95% CI = 1.003-1,141)] but not the odds of occurrence of BRD. Maximum THI is estimated using temperature and humidity, which in California's hot and dry summers may limit variability in THI, explaining its weaker significant association with risk of BRD (or lack of association with odds of BRD) compared with models for maximum temperature in this study. Calves exposed to high day temperatures and relatively low humidity may be experiencing heat stress that predisposes to BRD. Results of the current study suggest that heat abatement efforts should address heat stress at the microenvironment level to mitigate BRD in calves. Further research should investigate strategies to improve calf hutch systems, including hutch materials and design that may optimize ventilation, provide ample shade, spacing, cleanliness, and protection from heat.

Oxidative stress and imbalance of serum trace mineral metabolism contribute to bovine respiratory disease in dairy calves

Bovine respiratory disease (BRD) is the most common infectious cause of clinical disease and death in young calves. The study was undertaken to scrutinize a relationship between tissue damage by oxidative stress, concentrations of serum trace minerals and clinical status of calves during BRD. The method of clinical scoring and thoracic auscultation were used to screen and select infected calves. In this study, comparison of lipid peroxides (LPO), antioxidant enzymes and serum trace minerals was done between BRD infected and healthy subjects (18 calves in each group). The infected group was further divided into 3 subgroups according to clinical scores (CS) (5,6,7). The blood LPO levels were significantly higher in BRD infected calves. The antioxidative activities of superoxide dismutase, reduced glutathione, catalase and serum uric acid were significantly lower in BRD infected calves. The concentrations of trace minerals (copper, zinc, selenium) were significantly reduced during BRD. All hematobiochemical parameters varied proportionately with the CS of infected calves. These findings demonstrated simultaneous occurrence of increased oxidative stress and depletion of antioxidative trace minerals during BRD in calves. A strong correlation exists between severity of oxidative stress and CS of calves.

Assessment of dairy calves' microbiological environment using 3M™ Petrifilm™ bacteriology plates

Bovine respiratory disease complex is a major disease in dairy calves. Environmental factors such as microbiological air quality have been associated with greater risk of bovine respiratory disease in calves. Routine air sampling for microbiological testing has not been traditionally performed by practitioners, mainly because of the cost associated with air sampling machines. Here we present an alternative, cost-effective air quality assessment technique using 3M™ Petrifilm™ bacteriology plates. This method can determine total aerobic bacteria, coliform, yeast, and mold counts. We found that a 10-min contact time was optimal for assessing calf environments. In the calf pens, median (ranges) bacterial counts were 340 (90 to 840) cfu/plate for aerobic plate counts, 4 (1 to 11) cfu/plate for coliform counts, 4 (1 to 11) cfu/plate for yeast counts, and 42 (1 to 120) cfu/plate for mold counts. Based on our findings, we propose that this approach can be used to monitor air quality in dairy calf barns.

Early recognition of bovine respiratory disease in calves using automated continuous monitoring of cough sounds

Bovine respiratory disease (BRD) complex in calves impairs health and welfare and causes severe economic losses for the Stockperson. Early recognition of BRD should lead to earlier veterinary (antibiotic/anti-inflammatory) treatment interventions thereby reducing the severity of the disease and associated costs. Coughing is one of the clinical manifestations of BRD. It is believed that by automatically and continuously monitoring the sounds within calf houses, and analysing the coughing frequency, early recognition of BRD in calves is possible. Therefore, the objective of the present study was to develop an automated calf cough monitor and examine its potential as an early warning system for BRD in artificially reared dairy calves. The coughing sounds of 62 calves were continuously recorded by a microphone over a three-month period. A sound analysis algorithm was developed to distinguish calf coughs from other sounds (e.g. mechanical sounds). During the sound recording period the health of the calves was assessed and scored periodically per week by a trained human observer. Calves presenting with BRD received antibiotic and/or anti-inflammatory treatment and the dates of treatment were recorded. This treatment date reference served as a comparison for the investigation of whether an increase in coughing frequency could be related to calves developing BRD. The calf cough detection algorithm achieved 50.3% sensitivity, 99.2% specificity and 87.5% precision. Four out of five periods, where coughing frequency was observed to be increased, coincided with the development of BRD in more than one calf. This period of increased coughing frequency was always observed before the calves were treated. Therefore, the calf cough monitor has the potential to identify early onset of BRD in calves.