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|Dairy basics - Calf and Heifer Raising|
|Written by Stephanie Skernivitz|
|Friday, 17 May 2013 07:27|
Developing and validating a standardized scoring system for bovine respiratory disease tops the priority list for a team of veterinarians and scientists at the University of California – Davis, School of Veterinary Medicine and the Department of Animal Science.
The research team, with the assistance of dairy managers and staff, are knee-deep in a project that targets prevention, diagnosis and treatment of bovine respiratory disease in dairy calves.
“Classic diagnosis of BRD and decisions about how to treat affected calves are based on mostly subjective observations that don’t necessarily predict what’s actually happening within the calf’s respiratory system. This makes it difficult to identify calves when they first become sick,” says Sharif Aly, BVSc, MPVM, Ph.D., principal investigator, Veterinary Medicine Teaching and Research Center, UC Davis School of Veterinary Medicine.
“The scoring system will help veterinarians and herd managers identify sick calves based on the probability that a given calf's score is indeed indicative of BRD, hence allowing for more informed treatment decisions,” Dr. Aly says of the UC Davis project.
It is being funded by University of California, Agriculture and Natural Resources and is a subsidiary of a large USDA project titled “Integrated program for reducing bovine respiratory disease complex in beef and dairy cattle.”
“The scoring system will be used as a diagnostic tool to identify sick animals for treatment in a more timely fashion, hence improving animal welfare and minimizing the use of antibiotics to treat animals that are not suffering from BRD,” he adds.
According to Aly, BRD, which includes pneumonia, is the cause of 22 percent of all pre-weaned heifer deaths. Additionally, it is the most common cause of death post-weaning in dairy heifers.
Data from USDA's 1991 National Dairy Heifer Evaluation Project, Dairy 1996, Dairy 2002 and finally the most recent Dairy 2007 study, show that all identify BRD as the second most deadly disease in unweaned heifers and the most deadly in weaned heifers.
“Our role as care-takers of animals is to reduce disease burden and improve animal welfare. Hence it is imperative that we research BRD with the goal of reducing its incidence,” he says.
How the scoring system works
According to Aly, designing the weights (scores) for a BRD clinical sign should be based on BRD risk. Similarly, once the scores for all clinical signs assessed are added up, the cut-off for determining whether a calf has BRD should be evaluated for its accuracy through a validation study.
“Working closely with calf raisers on dairies, our goal is to standardize and validate a BRD scoring system that can be used for preweaned dairy calves. We plan on achieving our goal by first estimating the appropriate score that should be assigned to each BRD clinical sign,” he says.
The next step, according to the research team, is to simplify the scoring system by identifying whether a clinical sign is present rather than a gradient of the clinical sign's presentation, which researchers say may increase the scoring system’s reliability.
Lastly, a final goal is to validate the BRD scoring system on a large number of calves under different management systems.
“Validating the scoring system is important as it will help us estimate the system's diagnostic accuracy, specifically its ability to identify true BRD calves (sensitivity) and true non-BRD calves (specificity),” Aly says.
Progress to date
In June, dairy producers in California will get a survey seeking information about calf management practices on their dairies.
The survey responses, according to researchers, will give the study team a “snapshot” of how management practices associated with pneumonia are carried out on dairies throughout California.
Based on these responses, the project will enlist a subset of cooperator dairies to be involved in a detailed assessment of management practices in collaboration with the herd veterinarian.
As the project continues, the researchers will use the validated scoring system to follow calves and estimate incidence rates, treatment rates and death loss from birth to weaning on California dairies to provide additional individual animal data on risk factors, according to Aly.
Though the current project focuses on California, as it is in cooperation with California dairy producers and managers, the findings are expected to be applicable to dairies nationwide in the U.S., specifically southwestern states, which have similar environments and management practices to California dairies.
Benefit to producers
“The outcomes of this study are expected to add an objective means to identify BRD cases in the field by utilizing a validated scoring system that translates a total score into a probability of true disease status,” Aly says.
Users will be able to access the scoring system in English and Spanish to offer workers a tool to make an informed decision to treat or not treat.
The validated BRD scoring system and the detailed risk assessment of management practices on dairies will together make up a comprehensive BRD risk assessment tool, Aly says.
Upon completing the assessment, veterinarians and herd managers will receive recommendations to reduce risk of BRD in the herd’s calves and can plan discussions with other key decision makers on the dairy.
“Through better understanding of the risk factors for BRD, better prevention and control strategies can be developed for improving the health and welfare of dairy calves in California and beyond,” Aly says. PD
Stephanie Skernivitiz is a freelance writer based in Cleveland, Ohio.
TOP RIGHT: Dr. Sharif Aly is the lead researcher on this project.
MIDDLE: Dr. William Love, a Ph.D. graduate student, assisted by Paul Rossito (center), staff research associate and Dr. Sharif Aly (right), collects a sample from a calf.
BOTTOM RIGHT: This photo shows Dr. Sharif Aly auscultating a calf. Photos submitted by Dr. Sharif Aly.