Researchers create mastitis-resistant cows

WASHINGTON — United States Department of Agriculture (USDA) researchers have yielded mastitis-resistant dairy cows using gene-transfer technology.

The research, published in the April issue of Nature Biotechnology, promises to eventually change the way producers breed agriculture animals and veterinarians' care of them, says Robert Wall, an animal physiologist with ARS Biotechnology and Germplasm Laboratory in Beltsville, Md., who led the scientific team. Working with USDA, the researchers built a transgene that includes the genetic code for producing the naturally occurring antimicrobial protein lysostaphin.

"I think the real important aspect of this work is that we've shown for the first time that you can genetically engineer an agriculturally important animal to be protected against a commercially important disease," Wall says. "It's a new tool in the arsenal in protecting animals from disease and infection. We've demonstrated that for the first time, and others, I'm sure, will follow."

Major need

The dairy industry has long clamored for new tools to combat mastitis, noted by USDA to be the costly of all dairy cattle diseases with reported economic losses topping $2 billion annually. Antibiotics, vaccines and other drugs often fail to effectively fight the bacterium

Staphylococcus aureus

, a major cause of mastitis, USDA says. In addition, the antibiotics are a threat to food safety, USDA adds.

According to the research, antimicrobial proteins seem to be the answer. The gene that secretes lysostaphin comes from a non-pathogenic species of Staphylococcus that uses the protein to repel S. aureus. The scientists introduced the gene to three Jersey cows, where it killed S. aureus and protected the cattle from infection, the research shows.

Practical application

Although the researchers already have received producer requests for mastitis-resistant semen, application of the technology is a long way from widespread use, Wall says. Milk from the genetically altered dairy cows requires federal regulatory approval following food safety testing. Analysis is in its early stages, Wall says.

"We envision that 10 to 15 years from now when this research is mature enough to be used in dairy operations, the genetics will be able to be disseminated in frozen semen," he says. "We have to evaluate the quality of the milk produced from these animals to make sure its manufacturing properties aren't altered. We're a long way from the marketplace."