Some cattle in a salmonella-resistance trial did not become infected; these were always non-black.
received his Ph.D. in pharmacology, then had addi- tional training in pathogenic bacteriology, focusing on salmonella. He worked as a veterinary medical offi cer with the USDA doing research on antibiotic- resistant salmonella and is an international expert on the virulence of antibiotic-resistant salmonella in livestock. “In my work with the USDA, I performed infection experiments in cattle,” he says. Dr. Dayna Harhay, microbiologist/ molecular biologist at the Meat Safety and Quality Research Unit at the USDA’s Meat Animal Research Center, Clay Center, Neb., sent Carlson various strains of salmonella to create
experimental infections in 400-pound calves. Carlson sent lymph nodes from those calves back to Harhay to see if salmonella was present. “Some of the calves became very ill, but we occa-
sionally noticed an animal that was hard to infect,” says Carlson. “These individuals had natural resis- tance and were always non-black. Some were Red Angus, Hereford, Shorthorn, Red and White Holsteins, Piedmontese, Tarentaise, Salers, Simmental, etc.”
Complementary Genetic Research Continues In the research that sam-
“A few black cattle have 2
pled lymph nodes from car- casses in slaughter facilities around the country, the hides were off. Researchers didn’t know the breed or color of the animals. It would be interest- ing to do a study to identify red cattle, or non-black cattle, in feedlots where we know salmonella is present in the environment — and different color coats in the cattle. Salmonella prevalence
could be checked to see what the different percentages of positive lymph nodes might be.
74 The Cattleman August 2014
copies of the PSR gene and are partially resistant to sal- monella. The PSR gene does help in black cattle, but helps the most in non-black cat- tle with 2 copies of the PSR gene,” says Steve Carlson, D.V.M., associate professor, College of Veterinary Medi- cine, Iowa State University. All of the non-black cat-
tle with 2 copies of the gene are resistant to salmonella, whereas about 5 to 10 percent of black cattle with 2 copies are resistant. This data was obtained after the research-
ers looked at samples from more than 2,000 animals of these breeds: Angus, Barzo- na, Braunveih, Hereford, Peid- montese, Pinzgauer, Simmen- tal, Shorthorn and Tarentais. “We have found some
black cattle that resist salmo- nella and E. coli O157:H7. They have the PSR/PSR genotype plus an unknown complemen- tary genotype (PSRc/PSRc). We are now seeking inves- tors in the company to fund the research to identify this complementary genotype so that we can create a test for it as well,” he says.
thecattlemanmagazine.com
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