Researcher Works to Reduce Salmonella Risk in Ground Beef
By Aces Staff
May 6, 2003
May 6, 2003
URBANA--"Market dairy cows, a significant source of ground beef in the U.S., have a surprisingly high prevalence of salmonella," said Fred Troutt, professor of veterinary clinical medicine at the University of Illinois.
"Adding to this concern, the number of infected cattle often increases as the animals move from the farm to the slaughterhouse,” he said.
As a member of the Food-Animal Production Medicine Consortium, Troutt participated in two national studies on the prevalence of this bacteria in market dairy cattle.
"In one study, we found the overall prevalence of salmonella to be 23% of cattle sampled at slaughter, and on one sampling day, nine out of every 10 cows we sampled were carriers of salmonella," he said.
Salmonella is transmitted through fecal matter, and when the hides of cattle become contaminated with manure, the incidence of carcass contamination can increase.
He suggested a number of ways livestock handlers can reduce salmonella transmission.
Troutt says the way the animals are housed, the length of time they are kept there, and how often the bedding in the free stalls is cleaned are likely to play a role in salmonella transmission. Using recycled water to flush cattle housing systems may also transmit the organism and help maintain it in the environment.
Bird and rodent control is important because both are vectors of salmonella. “Barns should be built so that birds can't roost above feed and defecate in it. Cattle producers should make sure water is high enough that the cattle have access to clean, fresh water,” Troutt said.
Livestock workers also should not use the same equipment to scoop feed that they use to shovel manure or dead animals.
"We found that trucks picking up cattle at the farms were often contaminated with salmonella," said Troutt. “When cattle are loaded onto the truck, the organism can be left on the farm, and it can contaminate cattle that are picked up."
“We need to establish cleanliness standards and disinfectants that operate well in trucks,” Troutt said. "Cattle should be loaded on the truck, the truck should depart, and the truck should be disinfected before returning to the farm. People entering the farm should wear disinfected footwear."
In the slaughter facility, he said, strong precautions are necessary to make sure fecal matter doesn’t contaminate carcasses or workers’ hands.
In the last five years since the USDA issued new mandates, slaughterhouses are taking much more care in processing. They are washing the animal before it's slaughtered, experimenting with dehairing programs, vacuuming the carcass with steam, using a mild acid rinse to reduce surface contamination, and running the carcass through a steam pasteurization cabinet, said Troutt.
“We also need to identify human carriers of salmonella in meat-processing plants,” he said.
“Humans could be transmitting salmonella to the beef at times. The idea that an infection travels only in one direction doesn’t make sense,” he said.
Troutt said that scientists are working on vaccines to prevent the colonization of salmonella in cattle. They may also begin to use competitive exclusion practices, “exposing animals to a specific organism that will take up space in their gastrointestinal tract so the salmonella can’t attach.”
“In the meantime, we need to maintain research efforts, to answer some of the key questions and to move any solutions to the practical level so we can better control salmonella,” he said.