Newswise — It would be a costly project if small hog farms tried to implement monitoring programs similar to those that large-scale operations use to monitor the prevalence of Salmonella among the livestock. The good news that Iowa State University researchers Isabel Harris and Matthew Erdmann found is that hogs on small farms already have little or no Salmonella.
"These farms have very low levels of Salmonella," explained D.L. (Hank) Harris, an ISU Food Safety Consortium researcher and animal science professor. "They're traditional farms that don't use antibiotics."
Harris' research group surveyed 50 traditional family farms in the Midwest ranging in size from 20 to 150 sows. The pigs there are raised on open lots using management procedures with varying risks of contributing to Salmonella on the premises.
The researchers found that practices such as maintaining small herd sizes, limiting the use of vaccines and refraining from using growth-promoting antibiotics did not translate into high prevalence of Salmonella. But those practices apparently don't have as much impact on keeping Salmonella levels low as do other practices such as the use of meal feed and straw bedding, low stocking densities or rodent control.
The lesson here, Harris noted, is that avoidance of antibiotics by itself isn't enough to keep Salmonella out. The other factors play more important roles."It's a real plus for organic and traditional farming," he said.
"The difficulty comes in how they market their pigs. We know that they can get exposed to Salmonella on transport vehicles or when they're held before they're slaughtered. So here you've got this organic farmer doing a good job raising pigs and being welfare-conscious. But when he takes them to market they could be contaminated with Salmonella depending on how that phase is done."
One farming practice that helps avoid Salmonella is the "all-in, all-out" procedure. Herds of hogs are kept together in one cohort in one facility, moved out as one group and then replaced by another group after the facility is cleaned. The segregation of the groups helps prevent infection from new animals. Only 42 percent of the small farms surveyed by the ISU researchers used the all-in, all-out procedure.
Harris explained that small farms generally don't use the procedure, which is more common among the large corporate producers. He estimated that a farm would need to produce about 6,000 pigs a year to make efficient use of all-in, all-out.
"It's difficult to do unless you're farrowing every week," he said. "Most of the small farmers are probably farrowing by batch and they may farrow only once every two or three months."