Disease In Feedlot Cattle Research Articles

Associations between Weather Conditions and Bovine Respiratory Disease in Feedlot Cattle

Bovine respiratory disease complex (BRD) is the most common cause of disease in weaned cattle. Ambient environmental conditions affect nutritional requirements, metabolism, and BRD risk; however, data on associations between specific weather conditions and BRD morbidity in cattle are sparse. The goal of our study was to quantify associations between daily BRD incidence rates and preceding weather conditions in different lag periods (considering up to seven days from the current day of interest) in feedlot cattle.

Mannheimia haemolyticaand bovine respiratory disease

Mannheimia haemolytica is the principal bacterium isolated from respiratory disease in feedlot cattle and is a significant component of enzootic pneumonia in all neonatal calves. A commensal of the nasopharynx, M. haemolytica is an opportunist, gaining access to the lungs when host defenses are compromised by stress or infection with respiratory viruses or mycoplasma. Although several serotypes act as commensals, A1 and A6 are the most frequent isolates from pneumonic lungs. Potential virulence factors include adhesin, capsular polysaccharide, fimbriae, iron-regulated outer membrane proteins, leukotoxin (Lkt), lipopolysaccharide (LPS), lipoproteins, neuraminidase, sialoglycoprotease and transferrin-binding proteins. Of these, Lkt is pivotal in induction of pneumonia. Lkt-mediated infiltration and destruction of neutrophils and other leukocytes impairs bacterial clearance and contributes to development of fibrinous pneumonia. LPS may act synergistically with Lkt, enhancing its effects and contributing endotoxic activity. Antibiotics are employed extensively in the feedlot industry, both prophylactically and therapeutically, but their efficacy varies because of inconsistencies in diagnosis and treatment regimes and development of antibiotic resistance. Vaccines have been used for many decades, even though traditional bacterins failed to demonstrate protection and their use often enhanced disease in vaccinated animals. Modern vaccines use culture supernatants containing Lkt and other soluble antigens, or bacterial extracts, alone or combined with bacterins. These vaccines have 50-70% efficacy in prevention of M. haemolytica pneumonia. Effective control of M. haemolytica pneumonia is likely to require a combination of more definitive diagnosis, efficacious vaccines, therapeutic intervention and improved management practices.

Bovine respiratory disease in feedlot cattle: Phenotypic, environmental, and genetic correlations with growth, carcass, and longissimus muscle palatability traits1

Bovine respiratory disease (BRD) is the most costly feedlot disease in the United States. Selection for disease resistance is one of several possible interventions to prevent or reduce the economic loss associated with animal disease and to improve animal welfare. Undesirable genetic relationships, however, may exist between production and disease resistance traits. The objectives of this study were to estimate the phenotypic, environmental, and genetic correlations of BRD with growth, carcass, and LM palatability traits. Health records on 18,112 feedlot cattle over a 15-yr period and slaughter data on 1,627 steers over a 4-yr period were analyzed with bivariate animal models. Traits included ADG, adjusted carcass fat thickness at the 12th rib, marbling score, LM area, weight of retail cuts, weight of fat trim, bone weight, Warner-Bratzler shear force, tenderness score, and juiciness score. The estimated heritability of BRD incidence was 0.08 +/- 0.01. Phenotypic, environmental, and genetic correlations of the observed traits with BRD ranged from -0.35 to 0.40, -0.36 to 0.55, and -0.42 to 0.20, respectively. Most correlations were low or negligible. The percentage of carcass bone had moderate genetic, phenotypic, and environmental correlations with BRD (-0.42, -0.35, and -0.36, respectively). Hot carcass weight and weight of retail cuts had moderate, undesirable phenotypic correlations with BRD (0.37 and 0.40, respectively). Correlations of BRD with LM palatability and ADG were not detected. Low or near zero estimates of genetic correlations infer that selection to reduce BRD in feedlot cattle would have negligible correlated responses on growth, carcass, and meat palatability traits or that selection for those traits will have little effect on BRD susceptibility or resistance.

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.

Detection of respiratory and enteric shedding of bovine coronaviruses in cattle in Northwestern Turkey

Bovine coronavirus (BCoV) is an important cause of diarrhoea in calves, winter dysentery in adult cattle and respiratory tract disease in feedlot cattle. Serum, faecal and nasal swab samples were collected from a total of 96 cattle with clinical signs in 29 barns of 23 villages in Northwestern Turkey. The cattle were subdivided into 3 distinct age groups (0-30 days old, 4-12 months old and 2-7 years old). An indirect antigen-capture ELISA and an antibody-detection ELISA as well as geometric mean BCoV antibody titres were used to detect BoCV shed in the faeces and in the nasal secretions, respectively. Relationships between BCoV shedding and age group, seroconversion and clinical signs in cattle were also analysed. The rate of faecal shedding of BoCV was 37.1% (13/35) in 0-30 days old calves, 25.6% (10/39) in 4-12 months old feedlot cattle and 18.2% (4/22) in 2-7 years old cows. The overall rate of BCoV faecal shedding was 28.1% (27/96) in the cattle examined. Only one animal in the 4-12 months old age group was found to shed BoCV nasally. The analysis showed that there was a significant difference (P < 0.0001) with respect to faecal shedding between the clinical signs and the age groups. BCoV antibody titre in 50% of all cattle was < or =100 as detected by ELISA while 27.1% of the cattle had high titres ranging between 1,600 and 25,600. The seroconversion rate was 7.3% (7/96) in animals shedding BoCV in the faeces and 42.7% (41/96) in cattle negative for faecal shedding as detected by ELISA, and 20.8% of cattle with no seroconversion shed BCoV in the faeces. There was no statistically significant association between seroconversion and nasal or faecal BCoV shedding. These findings confirm the presence of BCoV infections in Turkey. Further studies are needed to isolate BCoV strains in Turkey and to investigate their antigenic and genetic properties.

Role ofMannheimia haemolyticaleukotoxin in the pathogenesis of bovine pneumonic pasteurellosis

Bovine pneumonic pasteurellosis continues to be a major respiratory disease in feedlot cattle despite the recent advances in our understanding of the underlying complexities of causation. The etiological agent, Mannheimia haemolytica, possesses several virulence factors, including capsule, outer membrane proteins, adhesins, neuraminidase, endotoxin and exotoxic leukotoxin. Accumulating scientific evidence implicates leukotoxin as the primary factor contributing to clinical presentation and lung injury associated with this disease. Unlike other virulence factors, leukotoxin shows cell-type- and species-specific effects on bovine leukocytes. Recent investigations have delineated the mechanisms underlying the target-cell-specificity of leukotoxin and how this contributes to the pathogenesis of lung damage. This review summarizes current understanding of the secretion, regulation, mechanisms of action and evolutionary diversity of leukotoxin of M. haemolytica. Understanding the precise molecular mechanisms of leukotoxin is critical for the development of more effective prophylactic and therapeutic strategies to control this complex disease.

Synergistic effects of concurrent challenge with bovine respiratory syncytial virus and 3-methylindole in calves

Abstract Objective To evaluate the potential synergy between bovine respiratory syncytial virus (BRSV) and 3-methylindole (3MI) in inducing respiratory disease in cattle. Animals 20 mixed-breed beef calves. Procedure A 2 × 2 factorial design was used, with random assignment to the following 4 treatment groups: unchallenged control, BRSV challenge exposure (5 × 104 TCID50 by aerosolization and 5.5 × 105 TCID50 by intratracheal inoculation), 3MI challenge exposure (0.1 g/kg of body weight, PO), and combined BRSV-3MI challenge exposure. Clinical examinations were performed daily. Serum 3MI concentrations, WBC counts, PCV, total plasma protein, and fibrinogen concentrations were determined throughout the experiment. Surviving cattle were euthanatized 7 days after challenge exposure. Pulmonary lesions were evaluated at postmortem examination. Results Clinical respiratory disease was more acute and severe in cattle in the BRSV-3MI challenge-exposure group than in cattle in the other groups. All 5 cattle in this group and 3 of 5 cattle treated with 3MI alone died or were euthanatized prior to termination of the experiment. Mean lung displacement volume was greatest in the BRSV-3MI challenge-exposure group. Gross and histologic examination revealed that pulmonary lesions were also most severe for cattle in this group. Conclusions and Clinical Relevance Feedlot cattle are commonly infected with BRSV, and 3MI is produced by microflora in the rumen of all cattle. Our results suggest that there is a synergy between BRSV and 3MI. Thus, controlling combined exposure may be important in preventing respiratory disease in feedlot cattle. (Am J Vet Res 1999;60:563–570)

Haptoglobin response to clinical respiratory tract disease in feedlot cattle

Abstract Objective To quantify haptoglobin response to respiratory tract disease in feedlot cattle, and to investigate its ability to predict disease outcome and response to antibiotic treatment. Design Randomized clinical trial. Animals 60 feedlot calves with clinical respiratory tract disease. Procedure Calves were randomly assigned to receive a standard antibiotic treatment regimen (TRT), or to observation pens without antibiotic treatment. Serum haptoglobin concentration was measured at initial and final examinations. Calves were examined for presence of gross pulmonary lesions at slaughter. Results Mean ± SD serum haptoglobin concentration at initial examination was 67 ± 108 mg/dl, with range of 0 to 508 mg/dl. Haptoglobin concentration at initial examination was similar for the TRT group and the group that did not receive antibiotic treatment, but at final examination, TRT-group calves had lower (P &lt; 0.01) mean values. Calves receiving antibiotic treatment had haptoglobin concentration at or near zero at final examination. Calves not receiving antibiotic treatment had only slightly lower mean haptoglobin concentration at final examination, compared with initial examination. Within treatment groups, haptoglobin concentration was similar for cases with different outcomes. Calves with gross pulmonary lesions a: slaughter had numerically higher, although statistically similar, haptoglobin concentrations at initial examination, compared with calves without lesions. Conclusions Feedlot cattle with clinical respiratory tract disease have a large and variable haptoglobin response. Antibiotic treatment resulted in lower serum haptoglobin values, although low values were not required for full clinical recovery. Clinical Relevance Serum haptoglobin concentration may be an indicator of response to antibiotic therapy, although it appears to be unrelated to case severity or need for treatment. (Am J Vet Res 1996; 57:646–649)

Serum haptoglobin concentrations in a population of feedlot cattle

Abstract Objective To determine serum haptoglobin concentrations in a population of feedlot cattle and evaluate their usefulness in predicting subsequent clinical respiratory tract disease. Design Prospective longitudinal study. Animals 366 beef calves. Procedure Serum samples were obtained at feedlot entry and 40 and 65 days on feed (DOF). Calves were observed daily for clinical signs of respiratory tract disease. The lungs of 144 of the calves were evaluated at slaughter for the presence of gross lesions of pneumonia. Results 58% of the calves had detectable serum haptoglobin concentration in at least 1 sample. The proportion of calves with detectable haptoglobin were similar at each sample collection time. A higher proportion of the calves had values &gt; 10 mg/dl at 40 DOF. The prcportion of calves observed with clinical disease during the 10-day period after the 40 DOF sample increased (P &lt; 0.10) as serum haptoglobin concentration increased. At 65 DOF, calves with serum haptoglobin value &gt; 10 mg/dl had a higher (P &lt; 0.05) rate of subsequent clinical respiratory tract disease than did calves with lower values. The proportion of calves with gross pulmonary lesions slaughter increased (P &lt; 0.05) from 39% among calves without detectable serum haptoglobin concentration in any of the 3 samples to 63% among calves with at least 1 observed value &gt; 10 mg/dl. Conclusions We observed associations between serum haptoglobin concentration and subsequent clinical respiratory tract disease and pulmonary lesions at slaughter. However, serum haptoglobin concentration alone is not adequate for prediction of clinical disease. Clinical Relevance The usefulness for cross-sectional sampling of serum haptoglobin concentration as a diagnostic tool for clinical respiratory tract disease in feedlot cattle appears to be limited.

Diagnosis of respiratory disease in feedlot cattle occurring after being in feedlot for 45 days

During 1985 eleven feedlots located in Kansas and Nebraska under direct health care programs instituted by the author, received a total of 372,175 cattle. There was a 7% morbidity rate in these cattle and a .65% mortality. Respiratory diseases accounted for 65% of the morbidity and the mortality during this period.&#x0D; Of the 26,674 cattle treated in these feedlots, 33% of them had been on feed for more than 45 days and of the 2,420 animals that died, 46% of these had been in the feedlot for more than 45 days.

Thromboembolic meningoencephalitis caused byHaemophilus somnusinfection in a bull calf — A new disease in New Zealand

Thromboembolic meningoencephalitis (TEME) caused by Huemophilus somnus infection was diagnosed for the first time in New Zealand in an eight month old bull calf. Clinical signs included pyrexia, excessive salivation, recumbency, opisthotonus and rigidity of the front legs. Multiple red, malacic foci (1-10 mm in diameter) were visible grossly on the surface of the cerebrum and cerebellum, and were scattered throughout the brain parenchyma. Histologically these lesions consisted of focal haemorrhage, necrosis and neutrophilic infiltration. Fibrin thrombi and colonies of gram negative bacteria were present in many small blood vessels within necrotic foci. An organism with the morphological and biochemical characteristics of Haemophilus somnus was cultured from the brain. Although TEME is an important disease of feedlot cattle in North America and Europe it is relatively uncommon in cattle grazing pasture and is therefore unlikely to become a major problem in New Zealand.

Experimental exposure of feedlot cattle to infectious bovine rhinotracheitis virus

An axiom of infectious disease research states that significant numbers of animals with typical clinical disease must be observed to provide data for analysis. The morbidity rate of naturally occurring bovine respiratory disease (BRD) in feedlot cattle is frequently great enough to provide adequate data. In 2 successive years, the low incidence of respiratory disease in feedlot cattle at the Veterinary Medical Research Farm precluded analysis of the data. An alternative to the chance occurrence of spontaneous disease was experimental induction of BRD. Of the etiological trial of BRD, stress, virus and bacteria, a virus component appeared to provide the most potential for a controllable system. Exposure of cattle to pasteurella has given unpredictable results. A BRD inducing level of stress would be very difficut to simulate in large numbers of cattle. Aerosol exposure of calves to bovine herpesvirus-1 and 4 days later to Pasteurella hemolytica has been reported to consistently produce fibrinous pneumonia. The relationship of this experimentally induced disease to “shipping fever” is not clearly understood.1 Although this model is useful for experiments designed with small numbers of calves, it did not fit the needs for a larger scale controlled clinical trial. Therefore, we elected to expose newly arrived cattle to infectious bovine rhinotracheitis virus (IBRV) in an attempt to initiate BRD. This report presents the results of trials, conducted on each of 4 consecutive years.

Effect of levamisole on respiratory disease in feedlot cattle

It has been suggested that the deworming dose of levamisole administered at the time of processing cattle into the feedlot could be immunostimulatory and result in a reduced incidence of respiratory disease. This controlled field trial was undertaken to evaluate the effect of a single dose of 6.0 mg/kg of levamisole administered at the time of processing on the incidence and severity of bovine respiratory disease (BRD) in feedlot cattle.

Clinical Management of Respiratory Disease in Feedlot Cattle

Clinical Management of Respiratory Disease in Feedlot Cattle

Health Management of Feedlot Cattle

An organized and systematic approach is necessary for the effective control and management of disease in feedlot cattle. Typically feedlots receive cattle of various types, under many different conditions from a variety of sources. The design and operation of typical feedlots is frequently conducive to the mixing of cattle from several sources, exposure of new arrivals to resident populations, and the influence of many stressors often combine to result in major outbreaks of disease. Many diseases, such as respiratory diseases, are highly complex and difficult to control by vaccination or therapeutics alone. Veterinarians should develop methods to monitor disease occurrence and evaluate management procedures in feedlots as part of their normal routine.

Experimental oxytetracycline toxicity in feedlot heifers

Oxytetracycline had been widely used at 11 mg/kg for the treatment of respiratory disease in feedlot cattle. The increased prevalence of resistant strains of Pasteurella sp. has resulted in recommendations for increasing the dose to 33 mg/kg or as much as 55 mg/kg. The 33 mg/kg dose given to seven normal feedlot heifers i/v for three successive days produced signs of nephrotoxicity but no deaths.