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Vaccination alone won't address overall reduction of Salmonella on a farm. Vaccine will protect pigs from economic loss, but other measures can also reduce the challenge load to Salmonella and other organisms shed in manure. To help identify those factors, Iowa State University researchers developed an audit form to predict Salmonella problems based on farm procedures. Several key factors were identified which producers can implement.

Pig Flow/Number of sources

All in/all out pig flow has a significant impact on levels of organisms in the environment. This may be due to the ability to clean and disinfect between groups, minimizing age spread in a population, reducing other disease pressure, or some combination of the above.

Limiting the number of sources is also protective for a group of pigs. As above, there may be many factors that provide the mechanism of protection. In a commercial system, limiting finishing groups to only one or two sources impacted the level of subsequent Salmonella exposure.

Sanitation

Proper sanitation reduces diseases spread by manure. However, using a disinfectant is not the same thing as disinfecting! For example, formalin based products require a minimum temperature to be effective. Dilution of products must be done properly or bactericidal activity may be reduced. Improper cleaning prior to disinfection can leave organic matter, including biofilm, which rapidly inactivates disinfectants, even if used properly. Biofilm is a clear, shiny layer of organic material (“slime”) that sticks readily to surfaces in the barn.

Other factors

Feeding methods may assist in lowering levels of Salmonella in the gut. Wet or fermented feeds, or those with added acids, have a lower pH. This may reduce contamination in feed or the gut. Pelleted feeds may also be higher risk than meal feeds for exposure to Salmonella. Misuse of feed medications may upset the intestinal flora, allowing Salmonella to overgrow.

Off site weaning, or using early weaning, may reduce Salmonella exposure. Given its widespread nature though, subsequent reinfections may occur. Other animals may also harbor Salmonella and spread it to pigs.

Transport to the packing plant

Even when every procedure is followed properly on the farm, pigs can be rapidly contaminated during the hours prior to harvest. When Salmonella were given in the nose of anesthetized pigs, the organism spread throughout the body within three hours, even when no organisms were swallowed. This included fecal culture of the organisms — allowing for carcass contamination if gut contents were spilled. Cleaning of pens at plants and limited holding times, along with segregation of high risk pigs, are options to reduce contamination during transport to and at the plant.

4th Salinpork Congress

A group of researchers met in Leipzig, Germany in September to discuss the most recent information regarding food safety in pork. The meeting has expanded from Salmonella to cover other topics relating to food safety of pork products. Proceedings of the 4th Congress are available for purchase at the website www.salinpork2001.com. The full text of the 3rd Congress is available free online www.isecsp99.org/.

More information

Dahl et al. Salmonella reduction at the farm level. Proc 14th International Pig Vet Society. 1996. Page 181.

Various Authors, Proceedings of 4th Salinpork, 2001.

Hurd et al. Rapid infection in market weight swine following exposure to a Salmonella contaminated environment. AJVR 62(8); 1194-1197.