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Can we use genetics instead of chemistry to control disease?

Alison Van Eenennaam Published on 23 December 2014
Cows in a pen

The most expensive health problem facing the cattle industry is bovine respiratory disease (BRD), or shipping fever.

This disease complex is triggered by a number of interdependent factors including stressors such as weaning and transportation, exposure to new viral and bacterial agents, acclimatization to a new location and the establishment of a pecking order among new penmates.

Despite improvements in weaning management, vaccines, therapeutic agents and feedlot handling and receiving procedures, the incidence rates of this disease have remained stubbornly unchanged for decades.

With this in mind, a group of researchers from land-grant universities throughout the country saw an opportunity to try a new approach – to tackle this problem using genetics, an approach enabled by the sequencing of the three-billion-base-pair bovine genome and the resulting advanced genotyping technologies, to address this problem.

Technological advances in the field of genomics mean it is now possible to track which regions of the genome are associated with animals that are less susceptible to disease.

The trick is to identify those regions, which is the objective of a five-year grant funded by the USDA titled “The Bovine Respiratory Disease Coordinated Agricultural Project,” or BRD CAP for short.

One of the primary aims of this large project is to reduce the prevalence of BRD in beef and dairy cattle by identifying genetic markers associated with BRD susceptibility and develop DNA-based selection tools that can be used to breed healthier animals.

A collaborative group of scientists and educators at Colorado State University, University of Missouri, New Mexico State University, Washington State University, the USDA’s Agricultural Research Service and University of California – Davis, led by project director Dr. Jim Womack at Texas A&M University, make up the team that is working toward this goal by combining expertise in research, education and extension.

An eight-member advisory board that includes veterinarians, industry representatives and scientists regularly reviews the project’s milestones and provides suggestions and advice on various aspects of the effort.

The genetic research component of this project, led by Dr. Holly Neibergs at WSU, is centered on the development of two large (2,000 animal) studies, one for dairy and one for beef cattle, that include 1,000 sick (diagnosed with BRD) and 1,000 healthy (control) individuals.

These populations are being used to estimate the heritability of BRD susceptibility (i.e., how much BRD susceptibility or resistance is due to genetics as opposed to other influencing factors in the environment) and to identify regions of the genome associated with illness.

This research is being accomplished by examining the genetic makeup of animals that are ill and comparing that to the genetic makeup of those that were in the same environment and yet remained healthy.

Analyses of this genomic information should reveal regions of the genome, or perhaps even genes, which are over-represented in healthy animals. Such regions or genes are then potential candidates for selection to produce cattle less susceptible to BRD due to their genetic makeup.

Selection for disease resistance is the holy grail for animal breeders as it uses genetics to prevent disease, thereby improving animal welfare, health and productivity, while minimizing the use of therapeutic treatments for sick animals – all outcomes that align with attributes of improved sustainability.

To date, a number of promising genetic markers have been identified in the dairy population, and efforts are under way to hone in on those areas and identify which genes are providing protection from disease.

Sample collection from a population of 1,000 sick and 1,000 healthy feedlot animals is almost complete, and similar analyses will be performed with those data. More information about this project can be found online (www.brdcomplex.org).

Realizing the importance of training the next generation of veterinarians and researchers, the BRD CAP also has an educational component. The education team, led by Dr. Milt Thomas at Colorado State, is incorporating the BRD CAP research results into courses and educational materials for undergraduate, graduate, veterinary and 4-H students.

A distance-learning course, titled “Applied Bovine Respiratory Disease Management,” has recently been launched through Colorado State University Online Plus.

Additionally, research information is incorporated into the material covered by the U.S. Dairy Education and Training Consortium (formerly the Southern Great Plains Dairy Consortium). Many undergraduate and graduate students have also been directly involved in laboratory and field work associated with research aspects of the BRD CAP project.

Finally, the extension team, led by Dr. Alison Van Eenennaam at UC-Davis, is responsible for translating the results to the industry and evaluating both the real-world costs of BRD to dairies and feedlots, and the cost-benefit of genomic solutions to this problem.

Several episodes of the National Cattlemen’s Beef Association (NCBA) TV show “Cattlemen to Cattlemen” have featured stories about the goals and progress of the BRD CAP, with the most recent episode having aired on Nov. 18, 2014.

In July of 2014, a symposium highlighting the most current research on this disease complex was presented to a group of more than 300 attendees, representing 35 states and 10 countries. Extension materials, covering topics ranging from cow-calf management to economic considerations related to BRD, are also being developed as part of the BRD CAP.

The overall goal of the BRD CAP project is to use the genomic information uncovered to provide tools that will enable producers to select for cattle with improved disease resilience, thereby providing a sustained reduction in the incidence of BRD in both the dairy and cattle industries.

Translation of cost-effective innovations and management practices to the industry is an important deliverable of this five-year project slated for completion in 2016.   end mark

PHOTO
Selection for disease resistance is the holy grail for animal breeders through the use of genetics to prevent disease. Photo by Paul Marchant

Alison Van Eenennaam
  • Alison Van Eenennaam
  • Cooperative Extension Specialist Animal Genomics and Biotechnology
  • University of California – Davis

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