As animals are going to slaughter with Salmonella already inside the carcass, specialists are considering what preharvest practices could be employed at feedlots to reduce the risk. This may involve use of a probiotic, or management to eliminate or reduce biting flies, Harhay says.

“Monitoring might show whether there are higher levels of Salmonella in the environment. After all, there are differences from one location to another. If certain practices can be identified that might help keep Salmonella levels down, then broad implementation of those practices might address this problem,” she says.

Loneragan says work is underway on vaccine technology as well, such as Pfizer’s Salmonella SRP vaccine. “We’re trying to identify where vaccine works and where it might not work. We’ve also been looking at a probiotic called Bovamine Defend, made by Nutrition Physiology Co. This also looks promising. Perhaps we can control this issue preharvest, or reduce it enough to have a meaningful impact,” he says.

Genetics is another area of focus, since some non-black cattle have been found to have two copies of a gene that makes them very resistant to Salmonella. This finding is being pursued by a company called PSR Genetics, in Scott City, KS.

Harhay adds the differences in Salmonella lymph node contamination between feedlots, and between dairy and feedlot cattle in the same region, would seem to indicate that interventions may be possible at the farm or feedlot level.

Not all Salmonella are dangerous

Salmonella can cause disease in cattle and humans, but there are many serotypes; not all of them are dangerous. Many that exist in cattle only rarely cause disease in cattle.

“Some are more pathogenic than others, in both animals and people,” says Guy Loneragan, Texas Tech University professor of food safety and public health. “S. newport and S. typhimurium are quite pathogenic and can cause substantial disease in cattle and people, yet the farther south we go, the more diverse collections of serotypes we find in cattle, and more total numbers,” he says.

“We often find a carcass that has at least one lymph node in which we can recover Salmonella. These animals are healthy, with no history of clinical disease. These diverse strains of Salmonella seem to get in from the environment or the intestines, and enter the peripheral lymph nodes. Our hypothesis is that much of the Salmonella we observe in these locations are getting into the animal through the skin,” he says.

Heather Smith Thomas is a rancher and freelance writer based in Salmon, ID.


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