Objective—To determine the distribution of
Escherichia coli O157:H7 in pasture-based cattle production
Sample Population—Two 100-km2 agricultural areas
consisting of 207 pasture, 14 beef-confinement, and
3 dairy locations within 24 cattle operations.
Procedure—13,726 samples from cattle, wildlife, and
water sources were obtained during an 11-month
period. Escherichia coli O157:H7 was identified by
use of culture and polymerase chain reaction assays
and characterized by pulsed-field gel electrophoresis
Results—Odds of recovering E coli O157:H7 from
feeder-aged cattle were > 4 times the odds for cowcalf
or dairy cattle. There was no difference in prevalence
for pastured versus confined cattle after controlling
for production age group. Number of samples
collected (37 to 4,829), samples that yielded E
coli O157:H7 (0 to 53), and PFGE subtypes (0 to 48)
for each operation varied and were highly correlated.
Although most PFGE subtypes were only
detected once, 17 subtypes were detected on more
than 1 operation. Ten of 12 operations at which E
coli O157:H7 was detected had at least 1 subtype
that also was detected on another operation. We
did not detect differences in the probability of having
the same subtype for adjacent operations, nonadjacent
operations in the same study area, or operations
in the other study area.
Conclusions and Clinical Relevance—Strategies
aimed at controlling E coli O157:H7 and specific subtypes
should account for the widespread distribution
and higher prevalence in feeder-aged cattle regardless
of production environment and the fact that adjacent
and distant cattle operations can have similar subtypes.
(Am J Vet Res 2004;65:1367–1376)
Objective—To evaluate effects of a Salmonella Newport siderophore receptor and porin protein (SRP) vaccine on cattle health and performance and on prevalence of fecal shedding of Salmonella bacteria in feedlot cattle.
Animals—1,591 beef cattle.
Procedures—Cattle were randomly allocated within a replicate (n = 10 replicates [20 total pens]), administered 2 mL of a Salmonella Newport SRP vaccine (n = 795 cattle) or a placebo (796), and revaccinated approximately 21 days after the first administration. Health and performance data were recorded by trained feedlot personnel who were blinded to treatment. Fresh fecal samples (n = 25) were collected from pen floors on days 0, 60, and 120 and within 24 hours of cattle harvest and were subjected to selective Salmonella culture and serotyping by laboratory personnel who were blinded to treatment. Pen-level mixed models were used to analyze data.
Results—Significant differences in fecal prevalence of Salmonella bacteria or health and performance variables were not detected between vaccinated and control cattle. Salmonella bacteria were recovered from all 10 replicates, and cumulative prevalence estimates ranged from 1.5% to 22%. Overall prevalence of fecal shedding of Salmonella bacteria was 10.2% and 10.9% in vaccinated and control cattle, respectively. Overall morbidity risk was 34.8% for both vaccinated and control cattle. Overall mortality risks were 1.9% and 1.1% for vaccinated and control cattle, respectively.
Conclusions and Clinical Relevance—In this setting, administration of the Salmonella Newport SRP vaccine in feedlot cattle had no effect on fecal prevalence of Salmonella bacteria or cattle health and performance.
Objective—To evaluate associations between economic and performance outcomes with the number of treatments after an initial diagnosis of bovine respiratory disease (BRD) in commercial feedlot cattle.
Animals—212,867 cattle arriving in a Midwestern feedlot between 2001 and 2006.
Procedures—An economic model was created to estimate net returns. Generalized linear mixed models were used to determine associations between the frequency of BRD treatments and other demographic variables with economic and performance outcomes.
Results—Net returns decreased with increasing number of treatments for BRD. However, the magnitude depended on the season during which cattle arrived at the feedlot, with significantly higher returns for cattle arriving during fall and summer than for cattle arriving during winter and spring. For fall arrivals, there were higher mean net returns for cattle that were never treated ($39.41) than for cattle treated once ($29.49), twice ($16.56), or ≥ 3 times (−$33.00). For summer arrivals, there were higher least squares mean net returns for cattle that were never treated ($31.83) than for cattle treated once ($20.22), twice ($6.37), or ≥ 3 times ($−42.56). Carcass traits pertaining to weight and quality grade were deemed responsible for differences in net returns among cattle receiving different numbers of treatments after an initial diagnosis of BRD.
Conclusions and Clinical Relevance—Differences in economic net returns and performance outcomes for feedlot cattle were determined on the basis of number of treatments after an initial diagnosis of BRD; the analysis accounted for the season of arrival, sex, and weight class.
Objective—To describe daily, hourly, and animal-to-animal effects on lying behavior in steers.
Animals—25 crossbred beef steers.
Procedures—Wireless accelerometers were used to record behavioral data for cattle housed in a drylot cattle research facility during two 20-day periods (winter 2007 [n = 10 steers] and spring 2008 ). Behavioral data were categorized into lying, standing, and walking behaviors for each time point recorded. Logistic regression models were used to determine potential associations between the percentage of time spent lying and several factors, including time (hour) of day, day of trial, and steer.
Results—Lying behavior was significantly associated with hour of day, and a distinct circadian rhythm was identified. Steers spent > 55% of the time between 8:00 pm and 4:00 am lying and were most active (<30% lying behavior) during feeding periods (6:00 am to 7:00 am and 4:00 pm to 5:00 pm). Model-adjusted mean percentage of time spent lying was significantly associated with study day and was between 45% and 55% on most (27/40 [67.5%]) days. Lying behavior varied significantly among steers, and mean ± SD percentage of time spent lying ranged from 28.9 ± 6.1 % to 66.1 ± 6.6%.
Conclusions and Clinical Relevance—Cattle had distinct circadian rhythm patterns for lying behavior, and percentage of time spent lying varied by day and among steers. Researchers need to account for factors that affect lying patterns of cattle (ie, time of day, day of trial, and individual animal) when performing research with behavioral outcomes.
Objective—To determine the usefulness of physiologic, behavioral, and pathological changes as objective indicators of early respiratory disease in calves with Mannheimia haemolytica pneumonia.
Animals—14 crossbred beef steers.
Procedures—Disease was experimentally induced in healthy calves through endoscopic pulmonary inoculation of M haemolytica. Calves were necropsied on days 1, 2, 3, 5, 7, and 9 after inoculation. Physical examination variables (rectal temperature, heart rate, and respiration characteristics), clinical illness score, and degree of activity were assessed 3 times daily beginning 4 days prior to inoculation and continuing throughout the study. Twice before inoculation and on days 1, 2, 3, 5, 7, and 9, arterial blood gas measurements, serum biochemical analyses, and CBCs were performed. Pedometers and accelerometers were used to monitor cattle behavior and activity throughout the trial.
Results—All calves became clinically ill after inoculation and had gross and histopathologic signs of bronchopneumonia. No variable was a reliable indicator of disease progression as judged by percentage of pulmonary involvement. However, activity as measured by total steps taken in a 24-hour period was lower after versus before disease induction.
Conclusions and Clinical Relevance—This single-pathogen challenge model successfully yielded clinical signs and pathological effects consistent with naturally acquired respiratory disease. Routine laboratory variables and subjective measures were not reliable indicators of lung involvement or the progression of pneumonia. However, activity, objectively measured with pedometers and accelerometers, appeared to be a promising indicator for early recognition of bovine respiratory disease.
To evaluate associations between weather conditions and management factors with the incidence of death attributable to bovine respiratory disease complex (BRDC) in high-risk auction-sourced beef calves.
Cohorts (n = 3,339) of male beef calves (545,866) purchased by 1 large cattle feeding operation from 216 locations and transported to 1 of 89 feeding locations (backgrounding location or feedlot) with similar management protocols.
Associations between weather conditions and management factors on the day of purchase (day P) and during the first week at the feeding location and cumulative BRDC mortality incidence within the first 60 days on feed were estimated in a mixed-effects negative binomial regression model.
Significant factors in the final model were weaning status; degree of com-mingling; body weight; transport distance; season; precipitation, mean wind speed, and maximum environmental temperature on day P; environmental temperature range in the first week after arrival at the feeding location; and interactions between distance and wind speed and between body weight and maximum environmental temperature. Precipitation and wind speed on day P were associated with lower cumulative BRDC mortality incidence, but wind speed was associated only among calves transported long distances (≥ 1,082.4 km). Higher mean maximum temperature on day P increased the incidence of cumulative mortality among calves with low body weights (< 275.5 kg).
CONCLUSIONS AND CLINICAL RELEVANCE
Several weather conditions on day P and during the first week after arrival were associated with incidence of BRDC mortality. The results may have implications for health- and economic-risk management, especially for high-risk calves and calves that are transported long distances.
Outcomes research entails the application of clinical- and population-based research methods to optimize the end results of health-care practices and interventions, delivering benefits and value to stakeholders.1 Widely used in human health care, outcomes research principles can assist health-care providers and their patients in making decisions regarding medical costs while weighing available treatment options. The overarching goal of health-care providers should be to achieve clinical outcomes and improve value for patients. Value, however, is not the same as low cost. Porter and Lee2 defined value as the health-related outcomes that matter to
Objective—To determine the accuracy of accelerometers for measuring behavior changes in calves and to determine differences in beef calf behavior from before to after castration.
Animals—3 healthy Holstein calves and 12 healthy beef calves.
Procedures—2-dimensional accelerometers were placed on 3 calves, and data were logged simultaneous to video recording of animal behavior. Resulting data were used to generate and validate predictive models to classify posture (standing or lying) and type of activity (standing in place, walking, eating, getting up, lying awake, or lying sleeping). The algorithms developed were used to conduct a prospective trial to compare calf behavior in the first 24 hours after castration (n = 6) with behavior of noncastrated control calves (6) and with presurgical readings from the same castrated calves.
Results—On the basis of the analysis of the 2-dimensional accelerometer signal, posture was classified with a high degree of accuracy (98.3%) and the specific activity was estimated with a reasonably low misclassification rate (23.5%). Use of the system to compare behavior after castration revealed that castrated calves spent a significantly larger amount of time standing (82.2%), compared with presurgical readings (46.2%).
Conclusions and Clinical Relevance—2-dimensional accelerometers provided accurate classification of posture and reasonable classification of activity. Applying the system in a castration trial illustrated the usefulness of accelerometers for measuring behavioral changes in individual calves.
To compare immune responses induced by 2 commercially available vaccines with a bovine herpesvirus type 1 (BHV1) component following intranasal (IN) administration to colostrum-fed calves.
90 male Holstein calves (ages, 5 to 14 days).
In a randomized complete block design, each calf received 2 mL (1 mL/nostril) of vaccine A (n = 30), vaccine B (30), or saline (0.9% NaCl) solution (30) on day 0. Blood samples were collected for determination of serum anti-BHV1 IgG titer, and nasal fluid (NF) samples were collected for determination of interferon (IFN)-α and IFN-γ concentrations and for secretory IgA titers against BHV1, Mannheimia haemolytica, and Pasteurella multocida at predetermined times for 42 days after vaccination.
All calves were seropositive for anti-BHV1 IgG, and the mean anti-BHV1 IgG titer did not differ significantly among the 3 groups at any time. Both vaccines induced significant transient increases in NF IFN-α and IFN-γ concentrations. On day 5, mean IFN-α concentration and the proportion of calves with detectable IFN-α concentrations for the vaccine A group were significantly greater than those for the vaccine B and control groups. On day 42, the mean NF anti–P multocida IgA titers for both vaccine groups were significantly greater than that of the control group.
CONCLUSIONS AND CLINICAL RELEVANCE
Both vaccines induced innate and acquired immune responses in calves with colostral antibodies. The magnitude of the IFN-α response and proportion of calves with detectable IFN-α differed between the 2 vaccine groups. Both vaccines appeared to enhance the IgA response against P multocida.
Objective—To characterize clinical and behavioral changes in calves following inoculation with Mycoplasma bovis and evaluate relationships between those changes and pulmonary disease.
Animals—22 healthy Holstein steers.
Procedures—20 calves were inoculated intranasally with < 108 CFU or > 109 CFU of M bovis. Calves were assigned a clinical illness score (CIS) on a scale of 1 through 4 twice daily on the basis of severity of cough, labored breathing, and lethargy. For each calf, distance traveled and time spent near the waterer, feed bunk, or shelter were determined via a remote location monitoring device. Calves were euthanized and necropsied 22 days after inoculation.
Results—13 calves became clinically ill after challenge inoculation; 3 calves were euthanized within 20 days. Among all calves, consolidation was evident in 0% to 79.9% of the lungs; extent of lung consolidation did not differ between the challenge dose groups. Distance traveled and percentages of time spent in proximity to the feed bunk and shelter were associated with CIS; calves with more severe disease traveled less distance and spent less time at the feed bunk and more time in the shelter. Distance traveled by calves was negatively associated with extent of lung consolidation (< or ≥ 10% of lungs affected); this effect was modified by trial day.
Conclusions and Clinical Relevance—Following inoculation with M bovis, calf behavior patterns were associated with both CIS and severity of pulmonary disease. Use of behavior monitoring systems may aid in recognition of respiratory tract disease in calves.