Measurement of total respiratory impedance in dogs by the forced oscillation technique

The resistance (R _rs) and reactance (X _rs) of the total respiratory system were determined at various frequencies in 14 healthy conscious beagle dogs. A pseudorandom noise pressure wave was produced at the nostrils of the animals by means of a loudspeaker adapted to the nose by a tightly fitting mask. A Fourier analysis of the pressure and flow signals yielded meanR _rs andX _rs, over 16 s, at frequencies from 2 to 26 Hz. The influence of the posture of the dog, the position of its head, the linearity of the respiratory system, the reproducibility of the method and the effects of upper and lower airway obstructions were studied. In sitting and standing healthy dogs with the head in the extended position,R _rs values increased progressively with frequency from 5.4±0.4 (SEM) cmH₂O L^–1 s at 6 Hz up to 8.8±0.7 cmH₂O L^–1 s at 26 Hz, the mean resonant frequency being 6.1±0.5 Hz. No significant differences were observed between measurements performed with the head in the normal or the extended position. In a recumbent posture, allR _rs values were increased butR _rs was still dependent on the frequency in the same way (7.1±0.7 cmH₂O L^–1 s at 6Hz up to 10.0±0.5 cmH₂O L^–1 s at 26 Hz). Tracheal compression also induced higherR _rs values without changes in the frequency dependence or in the resonant frequency.In anaesthetized dogs, airway obstruction was induced by inhalation of histamine (4 mg/ml for 5 min; theR _rs values tended to decrease with increasing frequency, and the resonant frequency was markedly increased.Abbreviations FOT forced oscillation technique - IV intravenous(ly)     

Nutritional and dietary interrelationships with diseases of feedlot cattle

Feedlot economics dictate that highly fermentable rations be fed, leaving the ruminant constantly on the edge of lactic acidosis. Consequently, a number of subtle changes in feed, environment, or management can tip the balance, causing ruminal acidosis. Even though the animal may not die from the immediate effects of a metabolic acidosis, there are sequelae such as mycotic rumenitis, hepatic abscesses, cauda vena cava thrombosis, and pulmonary arterial thromboemolism that may cause subsequent losses. Another condition, typically referred to as atypical interstitial pneumonia/acute bovine pulmonary emphysema is a sporadic cause of death in feedlot animals. This condition is sometimes linked to the feed or hypersensitivities such as dust. At present, it seems the condition is not linked with the above and part of the problem may be undiagnosed bovine respiratory syncytial virus BRSV infection.     

Acute phase proteins in naturally occurring respiratory disease of feedlot cattle

The aim of this study was to evaluate three acute phase proteins (APP) [haptoglobin (HPT), lipopolysaccharide binding protein (LBP) and transferrin (Tf)] in feedlot cattle with naturally occurring respiratory disease diagnosed by a calf health scoring chart (CHSC). Seventy-seven beef calves were observed for signs of Bovine Respiratory Disease (BRD) during the first 28 days after arrival at the feedlot. Fourteen cases and pen matched controls were selected based on the CHSC. BRD cases were defined as a score of ≥5, while controls were defined as a score ≤4. The mean CHSC score in cases was 6.9 which was significantly greater than the controls 2.8 (P < 0.01). Mean plasma LBP and HPT concentrations were significantly greater in cases than controls (P < 0.01). Our study results show that measurement of HPT and LBP could be useful in detecting respiratory disease in feedlot conditions. Transferrin concentrations between the two groups were not statistically different.     

Involvement of microbial respiratory pathogens in acute interstitial pneumonia in feedlot cattle

OBJECTIVE: To evaluate viral and bacterial respiratory pathogens and Mycoplasma spp isolated from lung tissues of cattle with acute interstitial pneumonia (AIP) and cattle that had died as a result of other causes. SAMPLE POPULATION: 186 samples of lung tissues collected from cattle housed in 14 feedlots in the western United States. PROCEDURE: Lung tissues were collected during routine postmortem examination and submitted for histologic, microbiologic, and toxicologic examinations. Histologic diagnoses were categorized for AIP, bronchopneumonia (BP), control samples (no evidence of disease), and other disorders. RESULTS: Cattle affected with AIP had been in feedlots for a mean of 1272 days before death, which was longer than cattle with BP and control cattle. Detection of a viral respiratory pathogen (eg, bovine respiratory syncytial virus [BRSV], bovine viral diarrhea virus, bovine herpesvirus 1, or parainfluenza virus 3) was not associated with histologic category of lung tissues. Bovine respiratory syncytial virus was detected in 8.3% of AIP samples and 24.0% of control samples. Histologic category was associated with isolation of an aerobic bacterial agent and Mycoplasma spp. Cattle with BP were at greatest risk for isolation of an aerobic bacterial agent and Mycoplasma spp. CONCLUSIONS AND CLINICAL RELEVANCE: Analysis of these results suggests that AIP in feedlot cattle is not a consequence of infection with BRSV. The increased, risk of isolation of an aerobic bacterial agent from cattle with AIP, compared with control cattle, may indicate a causal role or an opportunistic infection that follows development of AIP.     

Predicting bovine respiratory disease outcome in feedlot cattle using latent class analysis

Bovine respiratory disease (BRD) is the most significant disease affecting feedlot cattle. Indicators of BRD often used in feedlots such as visual signs, rectal temperature, computer-assisted lung auscultation (CALA) score, the number of BRD treatments, presence of viral pathogens, viral seroconversion, and lung damage at slaughter vary in their ability to predict an animal’s BRD outcome, and no studies have been published determining how a combination of these BRD indicators may define the number of BRD disease outcome groups. The objectives of the current study were (1) to identify BRD outcome groups using BRD indicators collected during the feeding phase and at slaughter through latent class analysis (LCA) and (2) to determine the importance of these BRD indicators to predict disease outcome. Animals with BRD (n = 127) were identified by visual signs and removed from production pens for further examination. Control animals displaying no visual signs of BRD (n = 143) were also removed and examined. Blood, nasal swab samples, and clinical measurements were collected. Lung and pleural lesions indicative of BRD were scored at slaughter. LCA was applied to identify possible outcome groups. Three latent classes were identified in the best model fit, categorized as non-BRD, mild BRD, and severe BRD. Animals in the mild BRD group had a higher probability of having visual signs of BRD compared with non-BRD and severe BRD animals. Animals in the severe BRD group were more likely to require more than 1 treatment for BRD and have ≥40 °C rectal temperature, ≥10% total lung consolidation, and severe pleural lesions at slaughter. Animals in the severe BRD group were also more likely to be naïve at feedlot entry and the first BRD pull for Bovine Viral Diarrhoea Virus, Bovine Parainfluenza 3 Virus, and Bovine Adenovirus and have a positive nasal swab result for Bovine Herpesvirus Type 1 and Bovine Coronavirus. Animals with severe BRD had 0.9 and 0.6 kg/d lower overall ADG (average daily gain) compared with non-BRD animals and mild BRD animals (P < 0.001). These results demonstrate that there are important indicators of BRD severity. Using this information to predict an animal’s BRD outcome would greatly enhance treatment efficacy and aid in better management of animals at risk of suffering from severe BRD.     

Association of bovine respiratory syncytial virus with atypical interstitial pneumonia in feedlot cattle

Thirty-three cattle with fatal respiratory tract disease were examined for gross and histologic lesions and for the presence of viral and bacterial agents in the lungs. Fifteen cattle had lesions characteristic of atypical interstitial pneumonia (AIP), and 18 had other respiratory tract diseases, including infectious bovine rhinotracheitis, shipping fever pneumonia, bronchopneumonia, pulmonary abscess, and edema of the trachea. Gross necropsy findings in the cattle with AIP were uncollapsed and emphysematous lungs; histopathologic findings included interstitial edema, thickening of alveolar walls, hyaline membrane formation, and hyperplasia of type-II pneumonocytes. The infective agents found in the lungs of the 33 cattle included bovine respiratory syncytial virus, bovine herpesvirus type 1, Pasteurella sp, mycoplasmas, and Corynebacterium pyogenes. Bovine respiratory syncytial virus was detected by use of immunofluorescence and immunoperoxidase on lung tissue sections; bovine herpesvirus type 1 was detected by these techniques and by isolation of the virus. Bovine respiratory syncytial virus was significantly (P = 0.01) associated with lesions of AIP (11 of 15), compared with those of other respiratory tract diseases (5 of 18).     

Risk factors for lower respiratory tract disease in a cohort of feedlot cattle

Using data collected from company lot records, potential risk factors related to feedlot management, the cattle, and climate were determined. The risk factors were analyzed by use of weighted multiple regression techniques to determine their effects on the incidence of lower respiratory tract disease in a cohort of 95 lots containing 17,696 cattle. The gender of the cattle, the number of days that groups of cattle filled a lot, pregnancy checking of heifers, and the average temperature change in the first 14 days in which the cattle were on feed significantly influenced the incidence of lower respiratory disease. The incidence of lower respiratory tract disease was most influenced by risk factors in the first 30 days on feed.     

Bovine respiratory disease in feedlot cattle: environmental, genetic, and economic factors

The objective of this study was to characterize genetic, environmental, and economic factors related to the incidence of bovine respiratory disease (BRD) in feedlot calves. Records from 18,112 calves representing 9 breeds (Angus, Braunvieh, Charolais, Gelbvieh, Hereford, Limousin, Pinzgauer, Red Poll, and Simmental) and 3 composite types (MARC I, MARC II, and MARC III) over a 15-yr period (1987 to 2001) were evaluated. Disease incidence was observed and recorded by station veterinary and technical staff. The incidence of BRD varied across years, with the annual observed incidence ranging from 5 to 44%. From 1987 to 1992, the annual average incidence generally exceeded 20%. However, in later years the annual incidence did not exceed 14%. The epidemiological pattern indicated that BRD infection increased dramatically after 5 d on feed and remained high until approximately 80 d on feed. Previous BRD infection during the preweaning period did not influence subsequent BRD infection in the feedlot. Steers were more likely to become sick with BRD than heifers; castration before entry in the feedlot may be a predisposing cause. Few significant differences among breeds were detected for BRD incidence. Adjusted solutions from mixed model analyses indicated that Herefords were generally more susceptible to BRD infection (P < 0.05) than MARC I and III composite types. Composite breed types had similar susceptibility compared with other purebred breeds. Mortality associated with BRD was greatest in Red Poll calves (9%) compared with the average over all breeds (4%). Estimates of heritability for resistance to BRD ranged from 0.04 to 0.08 +/- 0.01. When the observed heritability was transformed to an underlying continuous scale, the estimate increased to 0.18. Selection for resistance to BRD could be effective if phenotypes for BRD resistance were known. Thus, development of an inexpensive and humane method of challenging animals with BRD to determine resistance would be an important step in reducing the incidence of BRD. This study also demonstrated that producer-collected field data could be used for selection against this disease. The economic loss associated with lower gains and treatment costs for BRD infection in a 1,000-cattle feedlot was estimated as dollar 13.90 per animal, not including labor and associated handling costs.     

Tilmicosin as a single injection treatment for respiratory disease of feedlot cattle

Tilmicosin, a new semi-synthetic macrolide antibiotic, was evaluated in eight field trials as a single subcutaneous injection at dosages of 0 (placebo), 5, 10 and 20 mg/kg for the treatment of naturally occurring respiratory disease in feedlot cattle. Animals for these trials were selected from large groups of recently-shipped feeder cattle at the time clinical signs of respiratory disease and body temperature of 40.6°C or higher were observed. Treated animals were evaluated daily for 10 days and finally at day 28. Each animal was weighed on the first day and again on day 28. Animals that died were necropsied. All treatment dosages were effective in significantly lowering mortality, improving weight gains, lowering body temperature, and reducing the severity of clinical signs when compared to the placebo-treated controls. Body temperature was the only variable with statistically significant differences among the dose levels.     

Antibody titers against bovine coronavirus and shedding of the virus via the respiratory tract in feedlot cattle

OBJECTIVE: To describe patterns of seroconversion to bovine coronavirus (BCV) and shedding of BCV from the respiratory tract in feedlot cattle. ANIMALS: 1,074 calves in feedlots in Ohio, Texas, and Nebraska. PROCEDURE: Nasal swab specimens were obtained at time of arrival (day 0) and at various times during the initial 28 days after arrival at feedlots. Specimens were tested for BCV, using an antigen-capture ELISA. Serum samples were obtained at time of arrival and again 28 days after arrival; sera were analyzed for antibodies to BCV, using an antibody-detection ELISA. RESULTS: Samples from 12 groups of cattle entering 7 feedlots during a 3-year period revealed that 78 of 1,074 (7.3%) cattle were shedding BCV (range, 0 to 35.9% within specific groups). At time of arrival, 508 of 814 (62.4%) cattle had low (< 50) or undetectable BCV antibody titers. Seroconversion to BCV during the initial 28 days after arrival was detected in 473 of 814 (58%) cattle tested (range, 20.3 to 84.1 % within specific groups). In cattle shedding BCV from the nasal passages, 49 of 68 (72.1 %) seroconverted, and 472 of 746 (63.3%) cattle that were not shedding the virus seroconverted. CONCLUSIONS AND CLINICAL RELEVANCE: Bovine coronavirus can be detected in populations of feedlot cattle in the form of viral shedding as well as seroconversion to the virus. Although only a few cattle were shedding the virus at the time of arrival at a feedlot, most of the cattle seroconverted to BCV by 28 days after arrival.     

Laboratory diagnosis of respiratory diseases of cattle

The authors describe the procedure of laboratory diagnosis for bovine respiratory diseases: direct diagnosis by isolation and for identification of bacteria or viruses and indirect diagnosis by serological methods. They specify the restraints and limits of this diagnosis and the significance results which are obtained and connected with knowledge of anamnestic information.     

Evaluation of concurrent shedding of bovine coronavirus via the respiratory tract and enteric route in feedlot cattle

OBJECTIVE: To assess the relationship between shedding of bovine coronavirus (BCV) via the respiratory tract and enteric routes and the association with weight gain in feedlot cattle. ANIMALS: 56 crossbred steers. PROCEDURES: Paired fecal samples and nasal swab specimens were obtained and were tested for BCV, using antigen-capture ELISA. Paired serum samples obtained were tested for antibodies to BCV, using antibody-detection ELISA. Information was collected on weight gain, clinical signs, and treatments for enteric and respiratory tract disease during the study period. RESULTS: Number of samples positive for bovine respiratory coronavirus (BRCV) or bovine enteric coro navirus (BECV) was 37/224 (17%) and 48/223 (22%), respectively. Some cattle (25/46, 45%) shed BECV and BRCV. There were 25/29 (86%) cattle positive for BECV that shed BRCV, but only 1/27 (4%) cattle negative to BECV shed BRCV. Twenty-seven of 48 (56%) paired nasal swab specimens and fecal samples positive for BECV were positive for BRCV. In contrast, only 10/175 (6%) paired nasal swab specimens and fecal samples negative for BECV were positive for BRCV. Only shedding of BECV was associated with significantly reduced weight gain. Seroconversion to BCV during the 21 days after arrival was detected in 95% of the cattle tested. CONCLUSIONS AND CLINICAL IMPLICATIONS: Feedlot cattle infected with BCV after transport shed BCV from the respiratory tract and in the feces. Fecal shedding of BCV was associated with significantly reduced weight gain. Developing appropriate control measures for BCV infections could help reduce the decreased weight gain observed among infected feedlot cattle.     

Temporal distributions of respiratory disease events within cohorts of feedlot cattle and associations with cattle health and performance indices

Bovine respiratory disease complex (BRDC), the most common cause of post-weaning disease in North American beef cattle, is a multifaceted process involving pathogen, host, environment, and management factors. Although the importance of describing and evaluating the timing of BRDC cases has been recognized, a formal analysis of the temporal patterns of BRDC has not been described in the literature. Our objectives were to classify within-cohort temporal patterns of BRDC cases during the first 100 days at risk, using operational data from commercial feedlots, and then to evaluate associations among temporal patterns and common cohort-level measures of feedlot performance and health, while controlling for common potential confounders. We used retrospective cohort-level and individual animal health data (2000-2008) from 10 U.S. feedlots. We defined cumulative distributions representing the timing of cases within cohorts using the daily percentage of cases relative to the total number of cases within a cohort. Ward's hierarchical clustering method was used to group cohorts exhibiting similar cumulative distributions of BRDC cases. Linear mixed models and generalized estimating equations then were used to determine associations between temporal patterns and economically important measures of cattle performance (mean daily weight gain, total days on feed, and carcass measures) and health (mortality risk and retreatment risk) outcomes, while accounting for possible confounding variables (gender, arrival month, arrival year, arrival weight, arrival risk classification, cumulative morbidity, and the feedlot itself). Cluster analysis identified seven different cohort-level temporal patterns of BRDC cases. Our independent variable of interest (temporal pattern) was associated with mean daily weight gain, total days on feed, and carcass weight, and the estimated effects were modified by arrival weight category and risk classification. Temporal patterns also were associated with USDA measures of carcass yield and quality that largely affect carcass price. We also found associations among temporal patterns and health outcomes (cumulative mortality and retreatment risk), and these effects were significantly modified by arrival weight and cumulative morbidity. Our results are the first to demonstrate that there are several temporal patterns of BRDC repeatedly observed among cohorts of feedlot cattle, and that these BRDC patterns may differentially affect cattle health and performance.     

Seroepidemiologic studies of the agent of respiratory diseases in cattle

In a period of three years epidemiological studies were carried out in Styria concerning the occurrence of antibodies against BRSV (Bovine Respiratory Syncytial Virus), Adeno I Species 3-Virus, Adeno II Species 8-Virus, PI-III (Parainfluenza 3-Virus), IBR/IPV-Virus and Chlamydia. A total of 1376 serum samples were examined and showed different titers of specific antibodies against respiratory pathogens. 449 blood samples were submitted to serological examinations in the year 1984, 525 in 1985 and 402 in 1986. Antibodies against BRSV could be found in 17.4% of the sera or in 55.9% of the herds. Specific antibodies against Adeno I Species 3 occurred in 33.9% of the sera resp. in 74.2% of the units. 35.2% of the cows or 80.1% of the herds showed positive SN-titres against Adeno II Species 8. IBR/IPV-specific antibodies were detected in 2.3% of the sera resp. 3.8% of the herds. Antibodies against Chlamydia could be found in 8.8% of the cows or in 22.6% of the units. In the years mentioned above significant differences of antibodies against BRSV, Adeno I Species 3, Adeno II Species 8 and Chlamydia could be observed, but not against PI-III and IBR/IPV as well. By means of the Chi-Square-Test significant differences between Simmentaler, Austrian Brown Cattle and Holstein Friesian regarding antibodies against IBR/IPV and Adeno II Species 8 could be found. No significant differences between the serological results of herds, which contained on of the three breeds could be observed.