Search Results

You are looking at 1 - 10 of 34 items for

  • Author or Editor: Brad J. White x
  • Refine by Access: All Content x
Clear All Modify Search
in Journal of the American Veterinary Medical Association
in Journal of the American Veterinary Medical Association

Abstract

Objective—To evaluate and analyze data from controlled studies on the effectiveness of vaccinating cattle with commercially available viral antigen vaccines for mitigation of the effects of bovine respiratory disease complex (BRDC).

Design—Systematic review and meta-analysis.

Sample—31 studies comprising 88 trials.

Procedures—Studies that reported the effectiveness of commercially available bovine herpesvirus-1 (BHV-1), bovine viral diarrhea virus (BVDV), bovine respiratory syncytial virus (BRSV), and parainfluenza type 3 virus (PI3) vaccines for protection of cattle against BRDC or its components were included in the analysis. Studies or trials were categorized as natural exposure or experimental challenge and were further divided by the viral antigen evaluated and vaccine type (modified-live virus [MLV] or inactivated vaccine). Meta-analysis was performed; summary Mantel-Haenszel risk ratios were determined, and Forest plots were generated.

Results—In natural exposure trials, beef calves vaccinated with various antigen combinations had a significantly lower BRDC morbidity risk than did nonvaccinated control calves. In trials evaluating BHV-1 and MLV BVDV vaccines in experimental challenge models, vaccinated calves had a lower BRDC morbidity risk than did control calves; however, in experimental challenge trials evaluating MLV BRSV and PI3 vaccines, no significant difference in morbidity or mortality risk was found between vaccinated and control calves.

Conclusions and Clinical Relevance—Estimating clinical efficacy from results of experimental challenge studies requires caution because these models differ substantially from those involving natural exposure. The literature provides data but does not provide sufficiently strong evidence to guide definitive recommendations for determining which virus components are necessary to include in a vaccination program for prevention or mitigation of BRDC in cattle.

Restricted access
in Journal of the American Veterinary Medical Association

Abstract

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 [15]). 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.

Restricted access
in American Journal of Veterinary Research

Abstract

Objective—To determine potential associations between demographic and business management factors and practice size and growth rate in rural mixed-animal veterinary practices.

Design—Cross-sectional survey.

Participants—54 mixed-animal practitioners.

Procedures—A cross-sectional survey (96 questions) was electronically disseminated. Responses were collected, and outcomes (number of veterinarians [NV], growth in number of veterinarians [NVG], gross practice income [GPI], growth in gross practice income [GPIG], gross practice income per veterinarian [GPIV], and growth in gross practice income per veterinarian [GPIVG]) were calculated. Bivariate analyses were performed and multivariable models created to determine associations between survey responses and outcomes of interest.

Results—Survey respondents were from mixed-animal practices, and most (46/54 [85.2%]) practiced in small communities (< 25,000 people). Study practices had a median ± SD NV of 2.3 ± 1.9 veterinarians, median GPI of $704,547 ± 754,839, and median GPIV of $282,065 ± 182,344. Multivariable regression analysis revealed several factors related to practice size, including the number of associate veterinarians and veterinary technicians in the practice, service fee structure, and employment of a business manager. Typically, practices had positive mean growth in NVG (4.4%), GPIG (8.5%), and GPIVG (8.1%), but growth rate was highly variable among practices. Factors accociated with growth rate included main species interest, frequency for adjusting prices, use of a marketing plan, service fee structure, and sending a client newsletter.

Conclusions and Clinical Relevance—Mixed-animal practices had a large range in size and growth rate. Economic indices were impacted by common business management practices.

Restricted access
in Journal of the American Veterinary Medical Association

Abstract

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.

Restricted access
in American Journal of Veterinary Research

Abstract

Objective—To develop partial budgets of the economic costs of 2 test strategies for screening cattle for persistent infection with bovine viral diarrhea virus (BVDV).

Design—Partial budget analysis.

Animals—938 calves arriving at 2 stocker operations.

Procedure—Calves were tested to determine prevalence of persistent BVDV infection. Test strategies that were evaluated included a single-test strategy consisting of immunohistochemical staining of skin biopsy specimens from all animals and a 2-test strategy consisting of polymerase chain reaction (PCR) assaying of pooled blood samples followed by immunohistochemical staining of skin biopsy specimens from animals in pools for which assay results were positive. Breakeven costs (ie, cost of persistent BVDV infection per animal necessary to justify whole-herd diagnostic testing) associated with each test strategy were calculated as a function of disease prevalence and test cost.

Results—Apparent prevalence of persistent BVDV infection was 0.32%. Sensitivity and specificity of the PCR assay for pooled samples were 100% and 89.7%, respectively. Regardless of the prevalence of persistent BVDV infection, the break-even cost for the 2-test strategy was lower than the break-even cost for the single-test strategy. However, the economic advantage was greatest when prevalence was low.

Conclusions and Clinical Relevance—Results suggest that using a 2-test strategy to screen cattle for persistent BVDV infection, whereby the first test involves PCR assaying of pooled samples and the second involves immunohistochemical testing only of those animals represented in pooled samples with positive assay results, will reduce the cost of screening incoming feedlot cattle, compared with immunohistochemical testing of all animals. (J Am Vet Med Assoc 2005;226:249–254)

Restricted access
in Journal of the American Veterinary Medical Association

Abstract

Objective—To determine the relationship between rectal temperature at first treatment for bovine respiratory disease complex (BRDC) in feedlot calves and the probability of not finishing the production cycle.

Design—Retrospective data analysis.

Animals—344,982 calves identified as having BRDC from 19 US feedlots from 2000 to 2009.

Procedures—For each calf, data for rectal temperature at initial treatment for BRDC and various performance and outcome variables were analyzed. A binary variable was created to identify calves that did not finish (DNF) the production cycle (died or culled prior to cohort slaughter). A mixed general linear model and receiver operating characteristic curve were created to evaluate associations of rectal temperature, number of days in the feedlot at time of BRDC diagnosis, body weight, quarter of year at feedlot arrival, sex, and all 2-way interactions with rectal temperature with the probability that calves DNF.

Results—27,495 of 344,982 (7.97%) calves DNF. Mean rectal temperature at first treatment for BRDC was 40.0°C (104°F). As rectal temperature increased, the probability that a calf DNF increased; however, that relationship was not linear and was influenced by quarter of year at feedlot arrival, sex, and number of days in the feedlot at time of BRDC diagnosis. Area under the receiver operating characteristic curve for correct identification of a calf that DNF was 0.646.

Conclusions and Clinical Relevance—Rectal temperature of feedlot calves at first treatment for BRDC had limited value as a prognostic indicator of whether those calves would finish the production cycle.

Restricted access
in Journal of the American Veterinary Medical Association