The volume of veterinary information is rapidly expanding, and with each passing day, the knowledge gained during one's veterinary school education becomes increasingly outdated. Veterinary practitioners face challenges when trying to build on existing clinical knowledge with additional information from the scientific literature to make better clinical decisions. Although veterinary medicine is built on scientific principles, incorporation of information from the scientific literature into clinical decision making is challenging for both new graduates and experienced practitioners. One of the largest obstacles is the amount of time required to accurately assess scientific information; however, a systematic approach to literature review enhances
Many research articles published in well-respected journals describe studies with serious design flaws that limit their value for clinical decision making; therefore, it is important that clinicians critically evaluate the scientific literature they read.1 Methods have been developed to guide critical evaluation of published articles concerning randomized clinical trials2–4 and observational studies.5 The REFLECT2 (Reporting guidElines For randomized controLled trials for livEstoCk and food safety) and STROBE6 (STrengthening the Reporting of OBservational studies in Epidemiology) statements are guidelines intended to encourage standardized reporting of research and facilitate clinician evaluation of
Scientific literature can be used in veterinary practice to make better clinical decisions for the benefit of patients, clients, and society as a whole. Developments in the 20th and 21st centuries have provided tools that allow and compel veterinarians to move beyond simple clinical observations and experience when making judgments regarding health and disease of animals. Methods have been devised to control bias (systematic distortion of results away from the truth) and confounding (distortion of the apparent relationship between 2 variables by a third factor) in multiple types of research study designs, and these methods allow researchers to be more
Veterinary clinicians typically read the scientific literature to become better educated and thereby improve the quality of their clinical decisions. Whether this objective is met depends on the scientific validity of the studies evaluated and the similarity of the hypotheses tested to a specific clinical question. A focused approach to answering a specific clinical question or questions is important to avoid placing undue emphasis on preliminary data or extrapolating results beyond the populations to which they pertain. One approach to minimize potential misinterpretations and optimize time spent reading the literature is to use a strategic method of literature evaluation.
Objective—To compare economic outcome for herds
not exposed to Neospora caninum with that for herds
with various seroprevalences of N caninum infection
and evaluate 3 control strategies.
Design—Economic simulation model.
Sample Population—Beef herds with various seroprevalences
of N caninum infection.
Procedure—A 5-year simulation model was used.
Control strategies that were evaluated included
culling females that fail to calve, selling seropositive
females and purchasing seronegative replacements,
and excluding the daughters of seropositive dams as
Results—For a 5-year period with low prices for feeder
calves, endemic N caninum infection decreased
mean return to fixed assets by 22.2% when true seroprevalence
was 10% and by 29.9% when true seroprevalence
was 70%. Percentage decrease in return to
fixed assets was less dramatic when a 5-year period
with high prices for feeder calves was evaluated.
Analysis indicated that 2 control strategies (culling
females that fail to give birth to a calf and selling
seropositive female cattle and purchasing seronegative
replacement female cattle) were not likely to be economically
beneficial. The third control strategy (testing
the entire herd for N caninum infection and excluding
the female offspring of seropositive dams as replacements)
appeared to be a reasonable control strategy.
Conclusions and Clinical Relevance—For the
assumptions in the model, endemic N caninum infection
decreases return to fixed assets for cow-calf
herds. Of the potential control strategies evaluated,
testing the entire herd for N caninum infection and
excluding the daughters of seropositive dams as
potential replacements provided the best economic
return. (J Am Vet Med Assoc 2004;224:1597–1604)
Veterinary medicine has a unique role in modern society with regard to the production of a safe, wholesome, and economical food supply; protection from zoonotic diseases of livestock origin; and participation in the arena of biodefense. These roles are often collectively referred to as food supply veterinary medicine (FSVM).1–3 Employment opportunities in FSVM include those in the private and public sectors, such as the traditional curative care of livestock; production medicine consulting services; pharmaceutical and biologics firms; and positions related to food safety, biosecurity, process assurance, and biodefense. Several authors4–8 have asserted that the US veterinary
A series of surveys1–3 supported by the Food Supply Veterinary Medicine Coalition has highlighted issues related to the supply and demand for food animal veterinarians in the United States. Food supply veterinary medicine (FSVM) embraces traditional preventive care and treatment of livestock; production medicine consulting services; pharmaceutical and biologics industry employment; and employment related to food safety, biosecurity, process assurance, and biodefense. In contrast to results for the KPMG LLP study4 (often referred to as the Megastudy), several recent reports5–11 have asserted that the training and supply of food supply veterinarians does not meet
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.
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 estimate prevalence of cattle persistently
infected (PI) with bovine viral diarrhea virus
(BVDV) at arrival at a feedlot, prevalence of chronically
ill and dead PI cattle, and the magnitude of excess
disease attributable to a PI animal.
Design—Cross-sectional and cohort studies.
Animals—2,000 cattle at the time they arrived at a
feedlot, 1,383 chronically ill cattle from 7 feedlots, and
1,585 dead cattle from a single feedlot.
Procedure—Skin biopsy specimens were collected
and evaluated via immunohistochemistry. Cattle were
characterized as either PI or not PI with BVDV on the
basis of characteristic immunostaining. Follow-up was
obtained for the 2,000 cattle from which samples
were collected at arrival, and health outcomes were
determined for cattle exposed and not exposed to a
Results—Prevalence of PI cattle was 0.3% at arrival,
2.6% in chronically ill cattle, and 2.5% in dead cattle.
Risk of initial treatment for respiratory tract disease
was 43% greater in cattle exposed to a PI animal,
compared with those not exposed to a PI animal.
Overall, 15.9% of initial respiratory tract disease
events were attributable to exposure to a PI animal.
Conclusions and Clinical Relevance—Relatively few
PI cattle arrive at feedlots. However, those cattle are
more likely to require treatment for respiratory tract
disease and either become chronically ill or die than
cattle that are not PI. In addition, they are associated
with an increase in the incidence of respiratory tract
disease of in-contact cattle. (J Am Vet Med Assoc